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368 Cards in this Set
- Front
- Back
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Disease caused by microbes requires what 5 things?
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1. maintenance of organisms (reservoir) naturraly lives and replicates
2.transmission (from SOURCE) from one site to susceptible host 3.Adherence-sometime followed by invasion of host cells or tissues 4.Disease (pathology) 5.Evasion of host defense mechanisms |
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What is transmission?
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entry of organsims into host from Source
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Type of entry of microbes?
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*types of entry are not exclusive:
skin (wounds, burns) respiratory (direct droplets, aerosols) fecal/oral-food and water sexual transmission |
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Describe the immune response against transmission (1st line, second, third)
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1st: keratinized skin, sneezing, coughing
2nd: if break 1st line via wounds they encounter phagocytic cells and nonphag, NK cells 3rd: NOT directly involved in transmission step |
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How do bacteria and fungi adhere/enter?
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endocytosis
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How do viruses adhere/enter?
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endocytosis or fusion to host cell for entry
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How do parasites adhere/enter?
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endocytosis for entry
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External features of bacteria and fungi?
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capsules, surface Ag, flagella, fimbrae
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External features of viruses?
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envelopes(remnants of host cell they infected), peplomers(equivalent of surface Ag), capsids
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External features of parasites?
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surface Ags, mechanical attachment (ex: via teeth)
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What is the immune response against adherence? (1st, 2nd, 3rd lines of defense?
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1st: sneezing, coughing, flushing actions
2nd: phagocytic cells, nonphago, NK 3rd: Ab |
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How is the 1st line of defense evaded as microbes attempt to adhere?
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evaded by structural attachment features such as capsules and pili, secretions of hydrolytic enzymes
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How is the 2nd line of defense evaded as microbes attempt to adhere?
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evaded by capsules, molecular mimicry, intracellular replication, alteration of host cell fxn (downreg MHC) or genetic defects in phagocytic cells
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How is the 3rd line of defense evaded as microbes attempt to adhere?
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evaded by antigenic variation, secretions of proteases such as IgA protease
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What type of microorganism are bacteria (extracellular, intracellular ect)?
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extracellular
faculative intracellular obligate intracellular |
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What type of microorg are viruses?
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obligate intracellular
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What type of microorg are fungi?
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extracellular
faculative intracellular |
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What type of microorg are parasites?
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extracellular
faculative intracellular obligate intracellular |
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How does invasion of tissue/destruction of host cells occur by microbes?
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from replication (multiplication)of organism or due to production of exoenzymes (hydrolytic enzymes) by microorg
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Name 5 ways in which damage to the host can occur.
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1. replication of microorg (mechanical damage such as that caused by big parasite)
2. degradative/hydrolytic enzymes 3. exotoxins (secreted) and endotoxins (structural compoennt of microbe that causes damage when microorg dies) 4.build up of cellular debris, pH changes, competition for nutrients 5. collateral damage due to HOST immune response |
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What is the 1st line of defense of the host response against damaging microbial compents?
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detoxification by liver, production of new synaptic jxns
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How do microbes evade the host immune response?
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interference (inhibit phagosome fxn, antibody binding)
camouflage (hiding w/n cells, reduce expression of Ag) antigenic drift/shift (org recombin genomes to change the Ag that Ab were made against) destruction of immune system (kill immune cells) |
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all prokarytoes are ___
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bacteria
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Shape of bacteria?
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is usually round (coccus), rod-like (bacillus), or spiral (spirillum)
can be PLEOMORPHIC: variation in shape w/n same culture |
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What are the major bacterial groupings?
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gram +/ gram -
spirochetes (spiral, unique cell wall) Chlamydiae and Rickettsiae Mycoplasmas (NO cell wall) |
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What is a nucleoid and where would you find it?
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in bacteria: nuclear structure
-holds all the info for growth and maintence of the cell -no nuclear membrane -contains mesosome: 1 chromosome in nucleoid; closed, circular |
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What is a plasmid and where would you find it?
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Nuclear material of Bacteria
small, circular, nonchromosomal, dsDNA -capable of self-replicaition -**holds extra DNA NOT necessary for growth and maintence; replicates independent of nucleoid -*non essential genetic info |
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What is a mesosome?
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invaginations of PM that acts like spindle apparatus and anchors nucleoid to PM
fxn in DNA replication in bacteria and cell division |
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Do bacteria have double membrane bound organelles?
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NO!
70 S Ribosomes (necessary for translation)are found as wells as inclusion bodies |
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The cytoplasmic membrane of bacteria is the site of what?
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ATP synthesis, start of metabolism, transport system (PERMEASES)
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What do Permeases do in bacteria?
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part of cytoplasmic membrane
partipate in transport by targeting specific nutrients and pulling them across |
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What is the fxn of integral proteins in prok that makes it different than euk?
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in prok integral proteins are there for transport (like euk) but differ in that they act for ATP synthesis
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What do flagella do for bacteria? where are they ?
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external surface
*protein appendages for motility -contain protein called flagellin -found on many but not all bacteria therefore not a good target |
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Why aren't flagella a good target?
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b/c they aren't found on all bacteria
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What is the fxn of axial filaments on bacteria? what type of bacteria have them?
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for motility
found on outer membrane only found in Spirochetes |
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Why aren't axial filaments of bacteria good targets for antimicrobials?
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b/c covered over by outer membrane/sheath therefore not accesible by our immune system
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What is the fxn of Pili (fimbrae) in bacteria? which bacteria have them?
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for adhesion NOT motility, transport of bacterial material (sex pili)
-can consist of proteins fimbrins, pilins, adhesins -found ONLY in Gram - *two kinds: ordinary (adhesins) for adherance and sex pili (for attachement of donor and recipient in conjugation) |
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Are pili good antibody targets?
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yes! if Ab agains pili, then microbe can't adhere
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HOw do Pili participate in secretion? Which type are we concerned w/?
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they transport enzymes
Type III moves enzymes across periplasm into cytoplasm w/o stopping in b/n therefore damage host cell w/o evoking immune response |
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What is another name for glycocalyx? Composition?
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capsule/slime layer near cell wall
surrounding bacterial cells- -composed of mucopolysachharides and polypeptides (usually) |
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What is the purpose of the glycocalyx found on bacteria?
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adhesion
protection against : phagocytosis, dehydration, antibiotic penetration "firewall" for adherent resistance of antibiotics |
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is the glycocalyx immunogenic?
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yes: firewall for adherent resistance of antibiotics
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what is a biofilm?
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complex aggregation of microorganisms marked by the excretion of a protective and adhesive matrix.
-bacteria can form populations on surfaces of tissues linked together w/ type of capsule forming biofilm for adhesion and protections Ex: dental plaque and infections of prosthetic limbs |
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What is quorum sensing?
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ability of bacteria to communicate and coordinate behavior via signaling molecules.
When bacterial population reaches certain size (quorum), certain genes in bacteria turn on providing feedback signals Bacteria that use quorum sensing produce and secrete certain signaling compounds called pheromones |
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What are the 4 large classifications of bacteria what are they based on?
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based on cell wall
1. gram + 2. gram - 3. acid fast 4. cell wall-less |
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What is the difference in amt of peptidoglycan composing the cell wall of gram + vs -?
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gram +: thick mutiliayered peptidoglycan
gram -: single thin layer |
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Teichoic acids and Lipoteichoic acids are found in what types of bacteria?
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gram +
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fxn of teichoic and lipoteichoic acids?
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provide tissue specific adhesions
bonded to peptidoglycan help anchor the wall to membrane |
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Characteristics of peptidoglycan
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AKA: mucopeptide or murein
complex polymer that consists of a backbone of alternating NAG and NAM side chains linked by cross bridges by peptide bonds (think chain link fence) *site of action of certian antibiotics |
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Do gram + or - have a periplasm and what is it?
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Gram -
where the peptidoglycan is-arean b/n cell membrane and outer membrane |
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Do Gram + or gram - have outer membrane?
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gram -
LPS (PAMP) phospholipid bylayer in which instead of phospholipis there are lipopolysachharides -protects cell -contains porins for diffusion and permeases for transport |
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Structure of Gram - cell wall?
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outer membrane w/ lipopolysaccharides
thin layer of peptidoglycan periplasmic space |
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What are the surface Ag of Gram +?
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Teichoic and Lipoteichoic acids that are secreted to cell surface and then attached to peptidoglycan
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What are teh surface Ag of Gram-?
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LPS component:
Lipid A Core polysachharide O Ag |
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What is the M protein?
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type specifice M protein that surrouns lipotechoic acid in Gram +
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What part of LPS compenent is the endotoxin that achors into bilary?
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Lipid A: identical in all Gram -
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How is the core polysachharide of LPS different in different species?
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it is the same for all species: provides integrity to membrane
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What is the fxn of O Ag of LPS?
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used to distinguish serotypes (target for immune response)
unique to each bacteria *major Ag to elicit immune response -external component |
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is the LPS assembled then transported or vice versa?
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assembled than translocated to external outer membrane
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What bacterium have Acid Fast cell walls?
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Mycobacterium spp can cause Tb, leprosy
partially acid fast: Nocardia spp. |
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what does the acid fast cell wall contain?
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lipids, waxes and polysaccharides
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3 components of mycobacterium?
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1.arabinogalactan polymers coated w/ 2.mycolic acid making up a "cord factor"
3. trehalose dimycolate |
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Do acid fast microorg show virulence factor?
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yes. they are antiphagocytic: protect againt intraceullar killing therefore granuloma form ex: Tb
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why called acid fast?
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retains certain stains after being treated with acidic solution, and is thus classified as an "acid-fast bacillus
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Which bacteria are cell wall-less?
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mycoplasmas and ureaplasma
-mycoplasmas have no peptidoglycan contain sterols in PM cannot be stained w/ Gram |
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What do mycoplasmas have instead of cell wall?
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Mycoplasmas are unusual among bacteria in that most require sterols for the stability of their cytoplasmic membrane. Sterols are acquired from the environment, usually as cholesterol from the animal host
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What are the 2 repeating subunits in peptidoglycan?
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NAG and NAM
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how are peptidoglycan chains linked?
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by tetrapeptide crosslink in 3 dimensions
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Even though gram + and - both have peptidoglycan , what does gram - have that can protect it somewhat from antibiotics?
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LPS therefore more resistant
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What are the steps of peptidoglycan synthesis?
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1. produce NAG and NAM in cytoplasm
2.transport to membrane 3.attachement of sugars to bactoprenol; translocated to outside of cell 4.link sugars; transpeptidation |
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Fxn of autolysins?
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help degrade cell wall and get rid of damaged peptidoglycan for cell rebuilding
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What does protoplast imply? What cells are protoplasts?
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Have their cell wall entirely removed
Gram Positive Cells |
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What does speroplast imply? What cells are spheroplasts?
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have their cell wall only partially removed
Gram Negative cells |
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how do bacteria divide?
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binary fission: replicate mesosome and chromosome. Autolysins act on cell wall to allow elongation of cell. septum formation; 2 peptidoglycan layers move to bisect cell
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binary fission gives you what?
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clones--genetically identical daughter cells
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spore formation is for?
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survival
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do both gram + and - produce spores?
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only produced by some gram +
1 gram -: Coxiella burnetti |
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spores are formed in response to what?
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adverse conditions
for survival not reproduction |
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what does a spore contain?
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core that contains many cell components, chromosome, limited cytoplasm, coat with high concentration of calcium bound to dipicolinic acid, plus keratin-like protein
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What is the importance of the spore coat containing calcium dipicolinate?
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aids in heat resistance in the core..won't stain
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when a spore is formed, what is the mother cell that the spore is arising from called?
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sporangium
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Is cell division equal in the formation of an endospore?
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When sporulation occurs, cell division is unequal and the larger so-called "mother cell" envelops the daughter cell. The cell membrane of the daughter cell constitutes the inner membrane of the spore and the cell membrane of the mother forms the outer membrane .
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a vegetative cell is a ..
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metabolically active cell
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exoenzymes are also known as? and act where?
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also known as hydrolytic enzymes. they act outside of the cell
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are exoenzymes good antigens?
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yes!
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what are some examples of exoenzymes?
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lipases
collagenase (breaks down BM) protease hyaluronidase hemolysins Dnases |
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why do bacteria produce DNases?
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toxins can break down host cell releasing DNA that provides viscous environment. Bacteria w/ DNases break down DNA and move to surrounding tissues
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where are exotoxins synthesized?
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bacterial proteins synthesized internally
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what types of bacteria produce exotoxins?
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both gram + and -
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examples of diseases caused by exotoxins?
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tetanus
diptheria botulism |
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What are some roles of exotoxins in disease?
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-food poisoning by ingested exotoxin
-bacteria growing in wound or abscess produce exotoxin and cause local damage to host tissus like in gas gangrene -bacteria colonize, produce exotoxin and cause symptoms locally and systemically |
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What are the 3 types of exotoxins?
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A-B toxin
Membrane disrupting toxins superantigens |
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Most bacterial exotoxins fall into what category?
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A-B toxins
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What is the fxn of each unit of A-B toxins?
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B binds host cell R
A mediates the enzymatic activity *A=activity *B=binding |
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Explain the action of the cholera toxin.
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Cholera toxin is an A-B exotoxin. The B unit binds the R. Then A unit enters the cytoplasm and increases the activity of adenylate cyclase to increase cAMP leading to diarrhea
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Membrane disrupting toxins (category of exotoxin) is sometimes called?
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hemolysins (hydrolytic enzymes)
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What are the 2 types of membrane disrupting toxins?
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1. Pore (channel) former
2. Phospholipase (alpha toxin) |
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Why is phospholipase considered a type of membrane disrupting toxin? Isn't it an enzyme?
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it is named as an enzyme, but b/c it disrupts the membrane it is a toxin
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What is the action of superantigens as exotoxins?
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form bridges b/n MHC II of macrophages or other APC's and receptors on T cells
*NO specificity..polyclonal activation of T cells **cause cytokine storm of IL-2 and execessive production of other cytokines |
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Example of superantigen?
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TSST- toxic shock toxin of S. aureus
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is a endotoxin secreted?
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no..it is a structural component of the cell itself
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What does the Lipid A component of LPS of gram - act as?
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PAMP that triggers an innate response via PRR's on immune cells
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when does Lipid A of LPS exert its effects?
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when cells lyse..lysis of cells is due to MAC, C', phagocytosis, antibiotics
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what is the action of bacteriacidal antibiotic v/s bacteriastatic?
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bacteriacidal will kill the cell
bacteriastatic will not kill, but will inhibit division of microorg |
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What is the effect of low concentrations of Lipid A/endotoxin?
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low concentrations signal alarm reactions: fever, activation of C', activation of macs
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What is the effect of high concentrations of Lipid A/endotoxin?
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endotoxic shock characterized by hypotension and DIC: disseminated intravascular coagulation: is a pathological process in the body where the blood starts to coagulate throughout the whole body. This depletes the body of its platelets and coagulation factors, and there is a paradoxically increased risk of hemorrhage.
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What else besides Lipid A is considered endotoxic?
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peptidoglycan fragments (in huge concentrations), teichoic acids, and lipoteichoic acids of gram +
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toxicity of an endotoxin is linked to what?
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ability to activate complement cascade and activate cytokine system
Ex: if a gram - bacterium is phagocytosed and degraded, endotoxins will be released inducing the mac to produce IL-1..stimulates fever |
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What are the 4 appropriate responses of endotoxin in small amounts
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fever
vasodilation (PMNs increase kinins) increased antibody synthesis inflammation |
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Whatare the 2 inappropriate responses of endotoxin in large amts?
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shock (hypotension)
intravascular coagulation: DIC |
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chemical nature of endo vs/ exotoxin
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endo: LPS
exo: protein |
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relationship to cell of exo vs. endotoxin
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exo: extracellular, diffusible
endo: part of outer membrane |
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are endotoxins and exotoxins denatured by boiling?
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Endotoxins will not be..they will maintain structure
Exotoxins usually are affected by temp..it alters the protein structure |
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Are endotoxins and exotoxins antigenic?
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endo: poorly
exo: yes b/c forms toxoid |
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which are more potent: exo or endo?
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**exo (1 microgram)
endo (100 micrograms) |
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are both exotoxins and endotoxins specific?
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endo: low degree b/c Lipid A backbone is conserved
exo: highly specific |
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do endotoxins have enzymatic activity?
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no
exo usually do |
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what do strict (obligate) aerobes require?
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Obligate aerobes must grow in the presence of oxygen; they cannot carry out fermentation
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obligate aerobes must produce what?
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Catalase and superoxide dismutase: These enzymes detoxify peroxide and oxygen free radicals produced during metabolism in the presence of oxygen
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What is a facultative anaerobe? Do they contain both catalase and SOD?
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Facultative anaerobes can perform both fermentation, anaerobic respiration and aerobic respiration. In the presence of oxygen, anaerobic respiration is generally shut down and these organisms respire aerobically ** prefer O2
*have both Cat and SOD |
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What is an obligate anaerobe? Do they contain catalase and SOD?
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Obligate anaerobes do not carry out oxidative phosphorylation. Furthermore, they are killed by oxygen; they lack Cat and SOD
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What is an aerotolerant bacteria? Do they produce catalase and SOD?
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does not use oxygen; but can grow in presence (O2 is not toxic)
Only produce SOD |
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What is a microaerophilic bacteria? Do they produce both Cat and SOD?
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Microaerophilic bacteria grow well in low concentrations of oxygen, but are killed by higher concentrations
Sometimes have Cat, always produce SOD |
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What is a capnophilic bacteria?
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requires increased amts of CO2
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What 4 conditions determine whether a microbe grows optimally?
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O2
pH Temperature osmolarity |
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why is it important to take a biopsy of skin when suspecting Erysipeloid?
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b/c Erysipeloid bacteria are microaerophilic, they grow at PPO2 below 10%. If only scrape surface you will think it is due to an aerotolerant bug b/c they present similarly
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What is a mesophile?
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Bacteria that grow best at the middle of temp. range are referred to as mesophiles; which includes all human pathogens and opportunists
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What are the 3 categories of bacteria called based on temp?
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psychrophiles: cold (bacteria that can live in fridge)
mesophiles thermophiles: hot |
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What are the 3 categories of bacteria called based on pH?
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acidophiles
neutrophiles basophiles *most pathogens are neutrophiles |
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How is Staph aureus different in terms of osmolarity requirements?
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it can grow in presence of salt unlike other microorg
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What step is necessary for identification of most bacteria and occasionally other microorg?
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biotyping
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What is the basis of biotyping?
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anabolism + catabolism
catabolism = fueling anabolism = biosynthesis, polymerization, assemble |
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What is fueling?
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acquiring nutrients from the environment, production of precursor metabolites, and energy prodution via
DIFFUSION of O2, H20 and CO2 ENZYMATIC DEGRADATION |
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What do all transport systems for fueling utilize?
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permeases and thus are targets for antimicrobials
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What are the 3 transport systems of fueling?
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facilitated diffusion
active transport group translocation |
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What transport system of fueling is unique to bacteria?
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group translocation: phosphorylation linked transport taht requirs ATP and has enzymatic carrier proteins to speed up metabolism
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What is the most common pathway in bacteria for sugar catabolism?
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glycolysis
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What pathways does aerobic respiration require?
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Aerobic Respiration involves glycolysis and the tricarboxylic acid cycle
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What pathways does anaerobic respiration require?
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Anaerobic respiration includes glycolysis and fermentation
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What is the final electron acceptor in aerobic v.s anaerobic respiration?
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aerobic: oxygen
anaerobic: inorganic compounds like NO3 SO4 CO2 * do not have complete electron transport systems |
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What is the final electron acceptor in fermentation?
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organic metabolic intermediate
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Fermentation is important in ?
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determining metabolic pathway of the bacteria
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Fxn of SMAC?
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demonstrates fermentation or nonfermentation of Sorbitol. with fermentation get production of acids
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Fxn of enterotubes?
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contain various media demonstrating metabolic processes/end products
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Measurement of catalase production is impt for what type of bacteria?
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gram +
grow colonies, drop hydrogen peroxide in tube..if produces catalase see bubbling |
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Measurment of oxidase production is impt for what type of bacteria?
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gram -
tells you if org has complete electron transport system |
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bacterial growth is regulated by what?
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surface to volume ratio: too much cytoplasm, sensors say nutrient levels low-stimulate cell division
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what happens to bacterial growth if nutrient availability is low?
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once initiated must be completed
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In bacterial growth, what signals low metabolites?
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alarmones: trigger sporulation for survival
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What 2 methods can you use to measure bacterial cell growth?
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Haemocytometer- gives TOTAL count
Serial Dilution Plating-gives VIABLE count |
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Difference b/n Haemocytometer and Serial Dilution Plating?
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Haemo: does not distinguish b/n viable and nonviable cells ..gives TOTAL
Serial dilution: counts living cells/viable |
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What happens in the lag phase of population dynamics?
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Adjustment to new environment
Storage of precursors for cell division once it has started Growth of cell (volume to surface increases) Once surface to volume ratio becomes limiting, DNA synthesis begins/begin DNA replication |
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What happens in the log phase/exponential phase?
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Cell Division; number of new cells greater than cells dying
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what happens in teh stationary phase?
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Nutrients become limiting, toxic material accumulates
Number of new cells equal to number of cells dying |
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What happens in the decline/death phase?
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When cells begin to lose their integrity
Number of cells dying exceeds number of new cells SOME CELLS WITH SPORULATE TO SURVIVE REMEMBER: even when cells are dying they can cause damage! |
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During the decline phase of population dynamics, what increases?
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# of spores formed
no/few nutrients left stationary to maintain pop size |
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Describe the pathology that can occur during decline phase?
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LPS: Endotoxin Shock
LPS released, increse toxins Increase in toxins during this phase as they cells struggle to obtain nutrients |
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do bacteria have diploid or haploid genomes?
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haploid: genes usually present in one copy
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shape of bacterial chromosomes?
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most circular
some linear |
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Besides the genes that are essential for growth found in the single, circular chromosome, where are the specialized bacterial genes?
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on smaller extrachromosomal plasmids of non-essential info that are species specific
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what are the movable genetic elements that cannot self-replicate?
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transposons/insertion sequences "jumping genes" of non essential info
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what do transposons contain?
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insertion sequences and can transfer their info by inserting themselves into other loci in the same or other genetic elements (plasmids)
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what are phages?
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nuclear material incorporated into the bacterial chromosome after "lysogenic infection" ( prophage is a phage genome inserted as part of the linear structure of the DNA chromosome of a bacterium.; non essential info
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what is a bacteriaphage?
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a virus that infects bacteria
capable of inserting into bacterial chromosomes; get new genetic info into bacteria |
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what is a cistron?
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single coding gene/bacterial gene that is arranged into operon
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What is an operon?
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groups of one or more structural genes under the control of a single promoter. Possess recognition and binding sites for regulatory proteins called operators
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What is unique about the structural genes in an operon?
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they all contribute to a single metabolic pathway giving rise to POLYCISTRONIC messages
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what is a polycistronic message that is unique to bacteria?
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contains genetic info from all 3 genes of an operon onto a single message
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Bacterial chromosome replicates by means of a ____ structure
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replicon
Replicon think Replicate |
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what is a replicon?
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ds DNA circles capable of self replication; replicates bidirectionally (5'-3') from a fixed origin
Basic process: Theta model of Replication |
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What are the unique enzymes required for bactrerial replication that are only found in bacteria?
|
Certain topoisomerases: Gyrase (introduces supercoils into DNA) and Topoisomerase I (relaxes supercoils)
|
|
|
What are the 2 bacterial enzymes that are targets for antimicrobial agents?
|
gyrase
topo I Ab will bind to them and block repication |
|
|
what is the rolling circle method of replication?
|
process of nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA, such as plasmids, the genomes of bacteriophages, and the circular RNA genome of viroids.
in rolling circle replication one strand is replicated first (which protrudes after being displaced, giving the characteristic appearance) and the second strand is replicated after completion of the first one. *alternative method used by some plasmids and viruses |
|
|
what is the purpose of replicating via rolling circle method?
|
produce multiple copies of chromosome in short period of time: nick one strand, roll off other strand
|
|
|
What are 3 unique characteristics of transcription in prokaryotes?
|
1. no capping or tailing
2. no splicing of messages 3. polycistronic messages (single promotor) *transcription is making RNA from DNA template |
|
|
how many polymerases in bacteria?
|
1 RNA polymerase
eukaryotes have 3 |
|
|
what is the sigma factor?
|
prokaryotic transcription initiation factor that must be part of RNA polymerase for specific binding to promoter sites on DNA. *needed for accuracy and affinity of binding
|
|
|
new sigma factors allow new..
|
phenotypic expression
they can vary w/ organism recognizing different conserved seq in promotor *transcription is initiated by the binding of sigma factor to the promotor |
|
|
how does elongation of bacteria translation begin?
|
Elongation starts when the fmet-tRNA enters the P site, causing a conformational change which opens the A site for the new aminoacyl-tRNA to bind.
|
|
|
how is translation of bacteria regulated?
|
regulation of translation via transcription regulation b/c ***linked trascription and translation
|
|
|
what is a regulon?
|
genes in different locations, but all have promotor region that responds to the same regulatory protein: can include operans as well as single genes
|
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|
what is the subunit that allows RNA polymerase to recognize promotors?
|
sigma factor: bacteria use different sigma factors to allow expression of different sets of genes under ceterain conditions
|
|
|
What is the external regulator of gene expression?
|
TCTSs-two component signal transduction systems
signalbinding to surface R's on PM (sensor kinase). When bound,sensor kinase p-lates itself and the internal response regulator (cytoplasmic portion) which then activates transcription |
|
|
What are the 2 components of the external TCTSs?
|
sensor kinase: senses the signal and p-lates the second protein
response regulator: p-lated second protein that activates transcription |
|
|
What are the 2 internal regulators of bacterial gene expression?
|
operon
regulon |
|
|
What are the 2 pathways of internal gene exrpession in bacteria?
|
1. induction by substrate of enzymes coded by cistrons (catabolic pathway)
2. repression by product the enzymes synthesize (reg of anabolic pathway) |
|
|
what is attenuation?
|
type of repression
leader seq is in front of the operon..need operon for transcripition |
|
|
How does the TCTS coorelate with quorum sensing/
|
when bacteria reach a certain size (quorum), there is an increase in pheremone-like signals produced by bacteria that activate TCTS to induce new gene expression
|
|
|
what is the effect of point mutations on immune response?
|
certain microorg cause point mutations in their genome that result in chances to antigenic determinants and thus escape host immune response
|
|
|
chemical mutations may lead to...
|
antigenic variation: ex mehtylation represses genes
|
|
|
What are the types of chemical mutagens?
|
nucleotide-base exchange analogous ex AZT
polycyclic flat molecules Ex ethidium bromide (dye that affects ability of DNA to bind) DNA-reactive chemicals ex nitrous acid |
|
|
What are the types of physical mutagens?
|
radiation ex UV causes T-T dimers
|
|
|
what type of mutagen in bromouracil?
|
NT base analogue of chemical mutagens
|
|
|
what is the purpose of homologous DNA recombination in bacteria?
|
-stabilizes linear genomes (exogenotes) most linear DNA is not stable in cells
-requires long regions of homology -requires series of recomb enzymes -loss of some genes, replacement with new *Exchange of info. loss of original bacterial genes |
|
|
What is site specific recombination?
|
integration of foreing DNA where there is only a small site of homology (isertion seq) w/o losing genetic info..end result is the addition of new info, keeps old genes
|
|
|
Fxn of site specific recomb?
|
to STABILIZE linear DNA picked up from environment or other cells
may be used to insert circular DNA (foreign) into host chromosome=INTEGRATION of plasmid, temperate phage DNA or movment of transposons |
|
|
What are the 3 reasons for variation of gene expression?
|
1. allows phenotypic alteration of gene products recognized by the host immune system
2.contributes to dissemination of bacteria w/n a colonized hose 3.survival |
|
|
What is a phase variation?
|
switch genes on/off
|
|
|
What is antigenic variation?
|
altering the antigenic nature of genes: cassette switching(homologous DNA recombination), mutations, uptake and integration of mobile genetic elements
|
|
|
What is the def of transformation?
|
uptake of naked DNA from the environment
|
|
|
uptake of naked DNA from the environment is what process?
|
transformation
|
|
|
What is conjugation?
|
movement of DNA via pilus formation
|
|
|
movement of DNA via pilus formation is what?
|
conjugation
|
|
|
What is transduction?
|
movement of DNA via bacteriaphage
|
|
|
movement of DNA via bacteriaphage is called what?
|
transduction
|
|
|
Successful gene transfer is dependent on the absence of what?
|
restriction endonucleases
|
|
|
What does the shape of the bacteria have to do with recombination?
|
linear must go through site specific recombination while circular can be maintain autologously
|
|
|
what does it mean that cells must be competent to undergo transformation?
|
Some bacteria are able to take up DNA naturally. However, these bacteria only take up DNA a particular time in their growth cycle when they produce a specific protein called a competence factor. At this stage the bacteria are said to be competent. Other bacteria are not able to take up DNA naturally. However, in these bacteria competence can be induced in vitro by treatment with chemicals (e.g. CaCl2).
|
|
|
What is the most important mechanism of genetic exchange in gram pos microorg such as Strep pneumoniae?
|
transformation
|
|
|
At what phase does transformation occur?
|
log phase
|
|
|
What are the steps of transformation?
|
Uptake of DNA
Legitimate/Homologous/General Recombination : requires homology between the donor DNA and the chromosome and results in the substitution of DNA between the recipient and the donor. Recombination requires the bacterial recombination genes (recA, B and C) and homology between the DNA's involved. |
|
|
What is the difference in transformation b/n gram + and -?
|
Uptake of DNA by Gram+ and Gram- bacteria differs. In Gram + bacteria the DNA is taken up as a single stranded molecule and the complementary strand is made in the recipient. In contrast, Gram- bacteria take up double stranded DNA.
|
|
|
Transformation takes place b/n?
|
Because of the requirement for homology between the donor and host DNA, only DNA from closely related bacteria would be expected to successfully transform, although in rare instances gene transfer between distantly related bacteria has been shown to occur.
|
|
|
What method of gene tranfer is the following: movment of genetic info in a process that requires direct cell contant b/n 2 cells
|
conjugation
|
|
|
What mediates conjugateion?
|
F factor: The F factor is a circular piece of DNA that can replicate autonomously in the cell; it is an independent replicon and contains the tra operon: tra for transfer
|
|
|
What does the F factor code for?
|
One of the things the F factor codes for is the ability to produce a sex pilus (F pilus) on the surface of the bacterium. This pilus is important in the conjugation process
|
|
|
What must the recipient have or not have in conjugation?
|
The ability to act as a recipient is a consequence of the lack of the F factor.
|
|
|
What happens when an F+ cell integrates into chromosomal DNA?
|
After a F+ cell makes contact with a F- cell and transfers a ssDNA The F plasmid can become integrated into bacterial chromosome at various locations to produce Hfr (high-frequency recombination) donor strains. In addition, there is a high frequency of transfer of donor chromosomal genes
|
|
|
Why call Hfr?
|
Because donor strains with integrated F factors can transfer chromosomal genes to recipients with high efficiency, they are called Hfr (H igh f requency r ecombination) strains
|
|
|
Explain the transfer of chromosomal genes vs. F plasmid genes in conjugation
|
In matings between F+ and F bacteria, only the F plasmid is transferred with high efficiency to recipients. Chromosomal genes are transferred with very low efficiency, and it is the spontaneous Hfr mutants in F+ populations that mediate transfer of donor chromosomal genes.
|
|
|
What is an F' factor?
|
F' factors are produced by excision of the F factor from an Hfr. Occasionally, when the F factor is excising from the Hfr chromosome, donor genes on either side of the F factor can be excised with the F factor generating an F'. F' factors are named depending on the chromosomal genes that they carry.
|
|
|
What is generalized transduction?
|
Generalized transduction is transduction in which potentially any bacterial gene from the donor can be transferred to the recipient. If a recipient cell is infected by a phage that contains donor DNA, donor DNA enters the recipient. In the recipient a generalized recombination event can occur which substitutes the donor DNA and recipient DNA .
|
|
|
What is specialized transduction?
|
transfer of specific genes after integration of phage into bacterial chromosome: transfer of host DNA segments near the site of prophage integration
|
|
|
Diff b/n DNA transfered in specialized and generalized transducion?
|
generalized: transducing particle contains only host DNA
specialized: contains both viral and host DNA |
|
|
What happens in lytic replication? What form of transduction does this occur with?
|
occurs with generalized transduction
-linear phage dsDNA is convered to circular form after infection. -if the nutritional state of the host is favorable, most infected cells undergo lytic replication and makes many copies of itself, assembles new capsids and releases them. Sometimes in the assemble process, some capsids are packaged with bacterial chromosomes. That phage with bacteria then cannot transfer virus genes therefore no infexn |
|
|
What happens in lysogenic replication? What form of transduction does this occur with?
|
specialized transduction
-linear ds DNA infects cell and is converted to circular dna -if the nutritional state of the host cannot support production of large numbers of progeny phages, lysogeny is established. Proteins expressed from the viral DNa bind a specific seq on the circular viral dna to a similar seq on the circular bacterial dna. the viral proteins break both circular molecules and rejoin them so viral is inserted into host dna. NO replication occurs. Form a prophage that is under appropriate stimulation (UV or stress) is activated and undergoes lytic replication |
|
|
What are the 2 types of transposable elements/jumping genes?
|
insertion sequences-minimal genetic info reqd for transport
transposons-carry additional info, jump into and out of a plasmid *transposons pick up new gene every time they move. tend to code for virulence factors |
|
|
consequence of integration via transposable elements?
|
disruption of normal gene seq
insertion of new genetic info |
|
|
what genes control the movement of the transposon?
|
transposase
resolvase |
|
|
what is a pathogenicity island?
|
mobile dna element called a genetic island..could be a modified transposon that inserts virulence related genes w/n chromosome
*unstable, carry mobility genes *gene products include toxins, adhesins, antibiotic resistance |
|
|
are fungi eukaryotic or prokaryotic? bacteria?
|
fungi: eukaryotic
bacteria: prokaryotic |
|
|
fungi are commonly called?
|
yeasts, molds, mushrooms
|
|
|
do fungi have peptidoglycan?
|
All fungi are eukaryotic and have sterols but not peptidoglycan in their cell membrane
|
|
|
do fungi contain chlorophyll?
|
no, but they do have cell walls, filamentous structures and produce reproductive spores
|
|
|
what is the difference b/n spores in bacteria and fungi?
|
in bacteria they are for survival, in fungi they are for reproduction: sexual and asexual
|
|
|
what does it mean that most fungi are saprophytes?
|
they live off of dead or decaying organic material and contribute to its decomposition
|
|
|
what are fungi classified based on?
|
mode of sexual and asexual reproduction
|
|
|
what percent of fungi are known to be pathogenic to man?
|
<1%
|
|
|
describe the fungal cell wall
|
composed mainly of polysachharides:chitin, glucan and mannan
also Hydrophobins for adherence(b/c highly conserved, not good target for Ab) |
|
|
what is the fxn of hydrophobins? where do we see this?
|
part of fungal cell wall for adherence
|
|
|
what is contained in the cell membrane of fungi?
|
Ergosterol for fluidity, integrity, **anti-fungal target
|
|
|
describe the cellular components of fungi
|
eukaryotic nuclei, mitochondria and vacuoules
|
|
|
what components of fungi structure are good anti-fungal targets?
|
glucan (of cell wall)and ergosterol(of cell membrane)
|
|
|
describe the optimal fungi habitat.
|
strict (obligate) aerobes
prefers acidic environments for optimal growth but can adapt w/n tissue -wide range of temperature tolerance in environmental fungi |
|
|
what organism is a heterotrophic saprophyte?
|
fungi
produces cellulases, proteases, and nucleases |
|
|
what is a hydrogenosome?
|
hydrogenosome is a membrane-bound organelle of fungi. It produces molecular hydrogen and ATP.
|
|
|
what is the diff b/n yeast fungi and mold or filamentous fungi?
|
yeast: unicellular
mold: mulitcellular |
|
|
how do yeast fungi replicate?
|
asexually by budding
|
|
|
what type of fungi form long chains cold hyphae?
|
molds
|
|
|
what is hyphea?
|
filamentous subunits of molds which may be nonseptate(lack septa cross walls), aseptate (w/o regularly occuring cell walls) AKA coenocytic
|
|
|
a mass of hyphae is called what?
|
mycellium
|
|
|
when does dimorphism occur?
|
Dimorphism usually occurs when a free living fungus infects a living host.
|
|
|
what does monomorphic mean?
|
it is describing the life cycle of a fungi: one form, mold OR yeast only..once a yeast always a yeast
|
|
|
what does dimorphic mean?
|
2 forms: mold and yeast
With most fungi that cause systemic infections, the yeast is the parasitic form, and the mold form is found in the environment; can switch phenotypic expression based on temp, nutrients |
|
|
how do yeasts replicate?
|
Yeasts are unicellular organisms, normally ovoid or spherical in shape. Typically, they replicate by budding rather than binary fission.
|
|
|
what is a pseudohyphae?
|
produced by Candida albicans
-during budding, before a new cell wall is deposited to separate the two, buds fail to detach and may form a short chain of cells called a pseudohypha or germ tube |
|
|
How are fungi grouped?
|
4 groups based on reproductive structures: spores in sac, spores that re free, thick shell w/ spores and no form of sexual reproduction
|
|
|
what is a rhizoid?
|
anchors some fungi to tissue or environmental surface..extend off hyphae
|
|
|
Asexual reproductive structures of fungi are termed what?
|
Asexual reproductive structures are termed conidia. The condia can be formed at the tips of the growing hyphae on a specialized strucures called a conidiophore, directly off the hyphae, or within the hyphae themseles
|
|
|
sexual reproductive structures of fungi are termed what?
|
Sexual reproductive structures are termed spores and often are formed into complex structurs
|
|
|
Candida albicans is an example of what type of pathogenic fungi?
|
opportunistic: Candida is found as part of our normal flora on skin and mucosal membranes. It can cause infection if normal flora population dynamics are disturbed or if introduced into inappropriate body cavities.
Ex: oral thrush |
|
|
what determines the type of true pathogen when talking about fungi?
|
based on where they establish disease states: superficial/dermatophytes live on skin; subcutaneous are introduced via trauma; systemic cause disease when enter respirtory tract
|
|
|
what does it mean to be an opportunistic pathogen?
|
only cause disease in the immunocompromised: Human fungal infections in the United Kingdom are uncommon in normally healthy persons, being confined to conditions such as candidiasis (thrush) and dermatophyte skin infections such as athlete's foot. However, in the immunocompromised host, a variety of normally mild or nonpathogenic fungi can cause potentially fatal infections
|
|
|
what is the cause of the primary exposure to fungal disease?
|
*environmental exposure-EXOGENOUS: some are geo restricted
*overgrowth of normal flora (endogenous) |
|
|
do fungi cause disease in the healthy host?
|
no, they cause asymptomatic disease
in immunocompromised host they can cause disease |
|
|
waht is the primary response of the immune system against fungi?
|
inflammatory response with PMN's as the most important phagocytic cell. then removal of hyphae which are too large to be phagocytosed by degranulation
|
|
|
which Th arm is involved in response against fungi?
|
Th1 response and prolonged inflammatory response
*a Th2 response sets the stage for chronic fungal infxns..yikes! |
|
|
do you want an antibody response with fungi?
|
no..it will downregulate the cell mediated response and result in chronic disease
|
|
|
what determines the damage by fungi?
|
virulence factors, size of innoculum (#fungipresent) and host defenses
|
|
|
what are some examples of virulence factors that fungi use to cause damage?
|
-proteases
-capsules -melanin synthesis: acts as a free radical scavenger damaging host while protecting itself as well as being proinflammatory -intracellular growth (hide from immune response) |
|
|
what are the four major types of mycotic/fungal disease?
|
1. hypersensitivity
2.mycotoxicoses 3.mycetismus 4.mycoses |
|
|
what is mycotoxicosis?
|
type of mycotic disease the poisons man and animals by food products contaminated by fungi which produce toxins
|
|
|
what is mycetismus?
|
a type of mycotic disease
due to ingestion of toxic fungi like eating mushrooms |
|
|
What is mycoses?
|
a mycotic disease
actual infxn of the host by fungi *name for disease state |
|
|
what are the clinical manifestations of hypersensitiviy caused by mycotic infxn?
|
hypersensitivity pneumonitis
rhinitis bronchial asthma **hallmark of mycoses |
|
|
Mycotoxicoses and mycetismus are both due to the production of what?
|
secondary metabolites: Many moulds produce secondary metabolites (mycotoxins) that are highly toxic to humans. Ergotism is caused by eating bread prepared from rye infected with the fungus Claviceps purpurea.
|
|
|
what are the 2ndary metabolites produced by mycotoxicoses and mycetismus?
|
1. ergot alkaloids that cause vasoconstriction and smooth mm contraction
2. aflatoxins: potent carcinogens 3. psychotropic compounds |
|
|
what are superficial mycoses
|
The Superficial mycoses (or cutaneous mycoses) are fungal diseases that are confined to the outer layers of the skin, nail, or hair, (keratinized layers) rarely invading the deeper tissue or viscera. The fungi involved are called dermatophytes.
**no scarring |
|
|
What are subcutaneous mycoses?
|
involve dermis, subcutaneous tissues, muscle and fascia
ex: rose thorn penetrates leaving scar |
|
|
What are systemic mycoses?
|
invasive infections of the internal organs with the organism gaining entry by the lungs, gastrointestinal tract or through intravenous lines
|
|
|
what are opportunistic mycoses?
|
caused by fungi that are not true pathogens; they cause life-threatening disease only in immunocompromised pts or when introduced into inappropriate body cavities
|
|
|
Why would you perform direct LM examination and fluorescent microscopy?
|
to examine yeast vs mold
reproductive structures |
|
|
Why would you perform serology on fungi?
|
-dermal Hypersen testing
-*Dual sword Because fungi are poor antigens, the efficacy of serology varies with different fungal infections-may mount Ab response but not disease |
|
|
When does the presence of antibodies demonstrate exposure?
|
when an increase in titer is shown. increase titer of IgM is an acute infxn indicator
|
|
|
are parasites eukaryotic or pro?
|
euk cells
|
|
|
what is the difference b/n protozoans and helminths?
|
both parasites
protozoans: single cells helminths: multicellular w/ organ systems |
|
|
How do parasites obtain food?
|
by living on or w/n another organism
|
|
|
What is the diff b/n obligate and facultative parasite?
|
obligate: can live ONLY in association w/ host
faculatative: can live both in or on a host as well as in free form |
|
|
What are commensals?
|
parasites that benefit from the host w/o causing it any harm: establish infxn w/o causing disease
|
|
|
what is an endoparasite? ecto?
|
endoparasite lives inside the body
ecto: those which exist on the body surface |
|
|
How do you define the host when talking about parasites?
|
define host by what it provides for parasite
|
|
|
What is a definitive host?
|
the host in which the parasite lives its adult and sexual stage
|
|
|
what is an intermediate host?
|
the host in which a parasite lives as the larval and asexual stage (needs another host for life cycle)
|
|
|
What is a reservoir host:
|
other hosts that harbor the parasite and thus ensure continuity of the parasite's life cycle and act as additional sources of human infxn
|
|
|
What is a dead end host?
|
not reqd for development stage of organism but still cause disease in these hosts: parasites can't go through life cycle
|
|
|
what is a vector?
|
organism (usually an insect) that is responsible for transmitting the parasitic infxn (mosquito)
|
|
|
what makes protozoans fragile?
|
surrounded only by PM therefore increased susceptiblity to changeing environ, may requre vectors for survival
|
|
|
What are the 2 forms of protozoans?
|
trophozoite: motile, metabolicaly active, replicating form
cyst: dormant, non replicating form that is adapted for survival in environ |
|
|
how do protozoans cause disease?
|
large numbers of them
|
|
|
4 major divisions of protozoans?
|
amoebas
flagelletes sporozoans cilliates **based on motility |
|
|
what organ has a cuticle?
|
helminths..acts like our skin and is the target of attack by degran of eosinophils
|
|
|
what is the target for antimicrobials in helminths?
|
primitive muscular and nervous systems, digestive system.. they block peristalsis
|
|
|
how do helminths reproduce?
|
sexually w/ COMPLEX life cycles
|
|
|
low # parasites cuases?
high # parasites causes? |
low-infxn
high-disease *disease comes w/ burden |
|
|
helminths are divided into what groups based on ?
|
based on SHAPE
flatworms and roundworms |
|
|
source of parasitic disease is mostly?
|
exogenous: outside body
|
|
|
how is parasitic disease transmitted?
|
fecal oral: contaminated water (Katrina)
penetration through skin |
|
|
most parasitic infxns are subacute/chronic or actue?
|
subacute/chronic..dont know infected unti burden of parasite increases
|
|
|
what contributes to disease expression in parasitic disease?
|
burden of organsims and scar tissue
|
|
|
how do parasites inactivate host defenses though immunosuppression?
|
produce cytokines to down reg TH2 (humoral) arem of immune response in extracellular stage.
Intracellular stage: downreg TH1 response |
|
|
what is the main non specific response against parasites?
|
mast cells and eosinophils
|
|
|
what are the specific responses to parsites:
|
intracellular infxns: TH1
extracelular infxns: TH2 |
|
|
what is impt to understand about the immune response to parasites?
|
immunologic protection is rarely long term
|
|
|
what type of parsites are viruses?
|
obligate intracellular
|
|
|
when extracellular, viruses are considered?
|
inert..not to be considered living
|
|
|
What must virueses encode?
|
any reqd processes NOT provided by the host cell
|
|
|
A complete virus is a called a?
|
virion
|
|
|
What is a nucleocapsid?
|
complex of capsid and genome
|
|
|
explain the genome of virus?
|
RNA or DNA
linear, circular, segmented single or double stranded haploid, some diploid (HIV) |
|
|
what is the capsid of virus?
|
proteins that are helical or icosahedral in shape
|
|
|
What are some additional structures of viruses besides nucleocapsid?
|
envelope (protein containing lipid bylayer obtainined from budding off host)
peplomers (glycoprotein spikes) packaged enzymes (replicases, proteases) |
|
|
what is the diff b/n sloppy and non-sloppy envelope?
|
sloppy: lipid bilayer + host proteins like MHC
non-sloppy: lipid bilayer + viral proteins (peplomers) |
|
|
what does haploid mean? diploid?
|
haploid: 1 copy of genome
diploid: 2 copies of genome |
|
|
are both animal and plant viruses capable of being naked?
|
no, only plant virus
do not have naked helical animal virus |
|
|
shape of tobacoo mosaic virus?
|
non enveloped helical
|
|
|
waht is the most common shape of virus?
|
icosahedral capsid : 12 vertices and 20 triangular faces. each face may be composed of one or more capsomers. each capsomer may be composed of different polyeptides
|
|
|
what is the shape of adenovirus?
|
naked icosahedral virion
|
|
|
what make up capsomers of icosahedrals?
|
many different polypeptides
|
|
|
what are 2 classic examples of enveloped viruses?
|
HIV(diploid genome), influenze(segmented genome)
|
|
|
what are the 7 types of genomic replication in viruses?
|
1. dsDNA
2. ssDNA 3. dsRNA 4. ss+sense RNA 5. ss-sense RNA 6. ss+sense RNA w/ DNA intermediate in life cycle 7. partially dsDNA w/ RNA intermediate |
|
|
examples of dsDNA (w/n nucleus) genomic replication in viruses?
|
herpesvirus-linear
papillomavirus-circular |
|
|
herpesvirus-linear
papillomavirus-circular are examples of what type of genomic replication? |
dsDNA that replicates in NUCLEUS
|
|
|
examples of dsDNA(w/n cytoplasm) genomic replication in viruses?
|
poxvirus, variola virus
|
|
|
poxvirus and variola virus are types of viruses that use what type of genomic replication
|
dsDNA in cytoplasm
|
|
|
examples of ssDNA genomic replication in viruses?
|
parvovirus
|
|
|
parvovirus is an example of what type of genomic replication?
|
ssDNA
|
|
|
examples of dsRNA genomic replication in viruses?
|
rotaviruses
|
|
|
rotaviruses are examples of viruses that use what type of genomic replication?
|
dsRNA
|
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examples of ss+sense RNA genomic replication in viruses?
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poliovirus, rhinovirus, flavivirus
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poliovirus, rhinovirus, and flavivirus are viruses that use what type of genomic replication
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ss+sense RNA
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examples of ss-sense RNA genomic replication in viruses?
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influenza, measles
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influenza and measles use what type of genomic replication
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ss-sense RNA
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examples of ss+sense RNA w/ DNA intermediate genomic replication in viruses?
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retroviruses, HIV
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examples of partially dsDNA w/ RNA intermediate genomic replication in viruses?
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Hep B
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What are segmented genomes?
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each segment encodes for different proteins
Need to package all 8 segments together |
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what type of mixing do we see with segmented genomes? How does this occur
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genotypic mixing:Reassortment
EX: 2 diff strains of influenza infect same cell. we need to package segments together into a genome. only reqt is that we need 8 segments, but they can be from either strain therefore mixed progeny=reassortment progeny. still influenza, but different antigenic variant |
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why do we need to get vaccines for influeza every year?
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b/c of reassortment of progeny-leads to different antigenic variants
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what is phenotypic mixing?
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host cells infected w/ 2 non identical viruses. they mix but you get no changes in genome, possible alter host range, possibly resistant to Ab neutralization due to mixed peplomers on the progeny. 1st progeny has incrased tropism
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in phenotypic mixing, how do you end up with a pseudotype?
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entire coat from the other virus is surrounding the original genome "wolf in sheeps clothing"--masked as another virus
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can viruses replicat outside the host cell?
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NO!! they need to enter cells
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how can each type or strain of virus differ for the site of replication?
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tropism
permissveness: entry + replication (entry occurs by virus-Receptor interactions) |
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explain tropism in HIV
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tropism means the virus must bind to specific cell surface receptors to enter a cell. If a cell does not express these receptors then the virus cannot normally infect it. T trophic use CXCR4 R to enter T cells. M trophic use CCR5 to enter macrophages
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What is the fear involving the bird flu?
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Influenza A binds sialic acid
there are only slight differences b/n the sialic acid specificities of birds and humans. So the influenza might enter human and become tropic then lead to person person spreading |
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explain the steps in replication cycle of viruses?
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entry
1.attachement, 2 penetration, 3 uncoating capsids 4. macromolecules synthesis and replication 5. maturation assembly (assemble proteins + genome +capsule) and release (budding) |
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what are the 3 ways viruses penetrate?
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1. direct penetration by naked virus: binds to receptor sites on cellular mem, digest and enter
2. eveloped virus fuse w/ PM 3. enveloped virus enters by endocytosis into coated pit wich then fuses w/ endosome |
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when an eveloped virus fuses with the PM what type of fusion is this called?
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pH independent fusion
nuetral pH |
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When an enveloped virus is endocytosed into the cell into a coated pit then fuses with an edosome, what is this called?
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pH dependent fusion
acidic pH |
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how does Adenovirus enter cell?
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it is naked therefore it binds to R sites on cellular membrane, digests, and releases nucleic acid into cell
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herpes virus, paramyxoviruses and HIV enter cells how?
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enveloped viruses that fuse with PM (pH independent) by causing conformational change of R's (HIV and gp120)
can mediate cell-cell fusion forming syncytia: giant multinucleated cells |
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immediate early and early mRNA is synthesized when (during virus replication cycle)?
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before genome replication
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late mRNA is synthesized when (during virus replication cycle)?
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afer genome replication
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explain the assembly and release of naked and enveloped viruses.
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naked: form inclusion bodies then released
enveloped: assemble then bud off to obtain envelope |
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what is unique about Poxviruses?
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The replication of this virus is unusual for a virus with double stranded DNA genome because it encodes its own machinery for genome replication and therefore the replication occurs in the cytoplasm. Most viruses with a double stranded DNA genome replicate in the nucleus and use the host cells genome replication machinery.
**therefore they can have 2 membranes: 1 from Golgi then cytoplasmic membrane |
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The herpes virus derives its membrane from what?
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nucleus
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explain the general viral growth curve
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initially as the virus attaches, there is no change in viral titer. then as it disassebles into cell there is a decresae in titer. This is the start of the eclipse phase: infxn is not apparent b/c no virus particles. Then during replicatio (still eclipse) the titer stays constant. An the end of replication (and end of eclipse) there is a huge increase in viral titer and assembly: see virions
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what is the purpose of plaque assay?
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to determine viral titer (infectious particles) PFU= plaque forming unit
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What are the 4 types of viral infxns?
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1. abortive (nonpermissive cells: dont release new progeny virus)
2. inapparent (little to no damage) 3. acute/lytic (host cell death)-adnenovirus 4.persistent |
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what are the 4 types of persistant viral infexns?
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1. productive (nonlytic virus that keep budding virus out)
2. latent (limtd macromolecular synth but no virus synth) 3. transforming(DNA virus that integrates accidently. proteins then affect oncogenes..virus by itself is not suffiencient for oncogen) 4. slow (HIV) |
