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158 Cards in this Set
- Front
- Back
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What is the major cause of human death worldwide?
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Infectious disease
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Four assets that contribute to our problems with bacteria?
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ability to multiply rapidly
ability to respond rapidly to environmental changes small size rapidly change genetically |
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What are 4 mechanisms of genetic change?
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mutation
conjugation transformation- from environment transduction (involves bacteriophages) |
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Which kingdom has 70S ribosomes?
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prokaryotes
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True/False. DNA makes up 23% of the dry matter of a bacterium.
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False. RNA makes up 23%, DNA 3%
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Role of topoisomerase I
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relaxes supercoiling by making nicks in the DNA
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Role of DNA gyrase
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introduces supercoiling to circular DNA.
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What do nalidixic acid, ciprofloxacin, and novobiocin have in common?
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Antibiotics that target subunits of DNA gyrase
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Define strain.
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a population of organisms that descend from single organism
serovars- differ in cell surface biovars- differ biochemically morphovars- differ morphologically |
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5 steps in classifying or identifying an organsim
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isolation
colony morphology gram stain biochemical antigenic |
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General name for organisms that rquire special components to grow?
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fastidious
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If we wanted to distinguish gram + and gram- bacteria by culture, which medium would we use?
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MacConkey agar- is selective for gram - bacteria
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What is the Ziehl-Neeson stain used for?
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Acid fast organisms
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Name some biochemical characteristics used to distinguish bacteria
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surgar utilization
oxidase catalase indole production urease production |
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What phylogenic analysis is used to help classify species and determine whether a stretch of DNA has been recently inserted into a chromosome?
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G-C analysis
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What analysis is useful to determine how alike 2 bacterial strains are?
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nucleic acid hybridization, particularly of rRNA
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Organisms with an identical pulse field electrophoresis profile should be considered the same ______.
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strain
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What are 2 general mechanisms used to drive ATP synthesis?
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chemiosmosis- forming ion gradient across a membrane (respiration)
substrate level phosphorylation (fermentation) |
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What is an auxotroph?
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organisms that have found a niche closely associated with animals and require many different compounds for growth.
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What is a prototroph?
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Cells that have no requirements for organic compounds other than a carbon source.
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How do cells cope with fast growth rates?
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increase number of ribosomes
initiate a new round of DNA synthesis before the last round has finished |
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What is the purpose of the promotor?
The operon? |
Promoter- where RNA pol binds
Operon- where activators/repressors bind |
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What is a regulon?
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a bunch of operons regulated by a single element
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What event induces the SOS response?
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chemical or physical damage to DNA
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What condition induces the Quorum Sensing response of Staphlococcus?
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high cell density
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How does a bacterium sense DNA damage?
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DNA fragments bind to RecA
RecA catalyzes self cleavage of LexA LexA is a repressor for SOS genes |
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What is another name for the SOS genes?
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damage inducible genes (din)
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What is the cellular response to extreme heat?
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Attempt to renature damaged proteins or destroy them
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Which subunit of RNA polymerase involved in recognizing the promotor site?
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Sigma factor
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How is dramatic temperature sensed and heat shock response initiated?
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Sigma factor 32 is responsible for increased transcription of a set of proteins in heat shock response
DNAk is a chaperone that regularly degrades sigma 32, unless the more pressing issue of DNA damage occurs |
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What is the result of quorum sensing response in staphylococcus?
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Production of exotoxins- proteases, hemolysins, enterotoxins and toxic shock syndrome toxin
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Which molecular component is responsible for exotoxin secretion in high cell densities?
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RAP
binds TRAP increase in RNA III expression of toxic exomolecules |
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What is the difference between gram negative and gram positive bacteria?
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gram -: 2 membranes
gram +: one membrane and a thick cell wall |
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What is found in the periplasmal layer of gram - bacteria?
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peptidoglycan layer
degradative enzymes toxins? |
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What do b-lactamasees do?
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inactivate penicillin
found in periplasm of some gram - bacteria |
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True/False. When a bacteria rotates its flagellum CCW they move forward, and tumble when the flagellum rotates CW.
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True.
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What does the H stand for in E. Coli O157:H7?
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H antigen, is actually flagellin
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What kind of proteins are pili or fimbriae made up of?
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monomers called pilin.
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What type of proteins make up the sex pilus of gram - bacteria?
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lectins
they bind sugar |
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True/False. The type of pili on a bacterium are renewed only with the same type of pili.
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False. Is a method of evading the immune system.
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Why are gram - bacteria more resistant to antibiotics?
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Contain and can control porins that are in the outer membrane
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Bacteria with what feature form smooth glistening colonies on agar plates?
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Capsules
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What is responsible for the cell shape of the bacterium?
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Peptidoglycan
long polysaccharide chains linked together by peptide linkages |
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True/False. The peptidoglycan layer is very thick in gram - bacteria.
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False. Gram +
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What are the 3 components of LPS?
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lipid A
core polysaccharide O-specific |
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True/Flase. Teichoic acid is a component of gram + cell wall.
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True.
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A particular feature of Clostridium and Bacillus
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endospores
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At what stage is sporulation favored?
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starvation (carbon or nitrogen sources depleted).
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True/False. During sporulation and unequal division of cell cytoplasm, each side has a complete complement of DNA.
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True. Not sure why though....
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During sporulation, what becomes of the forespore?
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Becomes the spore.
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Define infectivity.
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The attack rate of a pathogen. Equals # of cases of disease/#exposed
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Define pathogenicity.
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# of cases of disease/ # infected
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What is the virulence?
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The relative capacity of a pathogen to cause damage in a host. (Diff from pathogenicity?)
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What are the 4 requirements for pathogen identification acc'd to Henle-Koch's Postulates?
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Organism must be present in every case of the disease
Organism must not be present in other diseases or normal tissues Organism must be isolated from tissues in pure culture Organism must be capable of inducing disease under controlled conditions and re-isolated |
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How does one identify virulence factors?
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inactivate gene associated and observe decrease in virulence
transferring suspected gene to non-virulent organism and conferring virulence |
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Define saphrophyte.
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Organism that survives of decaying organic matter.
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What are the steps of infection?
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Exposure
Transmission Attachment and Colonization Invasion and Dissemination Multiplication Shedding |
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What are three types of mechanical transmission?
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Fomite
Vector-borne Inoculation (contaminated needle or bite wound) |
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What bacterial enzymes assist in invasion of host tissues?
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hyaluronidase
collagenase phospholipase hemolysins coagulase protease |
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Ability of pathogen to either evade or breach localized host defenses
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invasion
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ability of pathogen to evade or breach host immune defenses and invade systemically
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dissemination
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What types of infection wind up spreading to other individuals by contact transmission?
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Urogenital
Skin Ocular |
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Organisms disseminated in which part of the body often rely on vector-borne transmission?
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blood
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What are three ways disease can be described in a population?
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sporadic: separate scattered events
endemic: occurs with predictable regularity epidemic: occurs at a frequency in excess of expected |
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Where is endotoxin found?
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In the cell wall of gram - bacteria
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True/False. Exotoxins are proteoglycans produced by gram - or gram + bacteria.
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False. Proteins produced by either gram+ or gram-
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What are some examples of diseases that are solely caused by an exotoxin?
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anthrax
tetanus botulism dephtheria cholera |
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True/False. Exotoxins are protein in nature, heat and acid labile and sensitive to proteolytic enzymes.
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True.
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True/False. Exotoxins are all cytotoxic.
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False. Many merely alter cell function.
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What are the three basic categories of exotoxins?
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AB toxins act intracellularly
membrane disrupting toxins superantigens |
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What are the roles of the 2 domains of AB toxins?
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A- responsible for enzymatic activity
B- responsible for binding |
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True/False. The AB domains of exotoxins are always found on separate subunits.
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False. Ex- diphtheria toxin, pseudomonas exotoxin A, and tetanus toxin
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Which subunit of the cholera toxin is for GM1 receptor recognition?
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B subunit
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Define cytotonic and give an example.
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A toxin that alters cell function but is not cytotoxic
cholera toxin |
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ADP ribosylation is a common biochemical activity of what category of toxins?
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AB toxins.
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What is the mechanism of ADP ribosylation by cholera toxin?
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Ribosylates the stimulatory component of AC
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True/False. Pertussis toxin binds to the inhibitory component of AC enzyme, resulting in decreased cAMP.
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False. It does bind the inhibitory unit, but still acts to raise cAMP.
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How does the mechanism of action of E.Coli ST differ from cholera toxin?
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Stimulates production of cGMP but with similar results
Does not seem to require cell entry? |
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What is a classic example of a single peptide toxin?
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Diphtheria toxin
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What is the mechanism of diphtheria toxin?
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binds to target and is internalized in a vesicle
enters the cytoplasm in response to pH change inside vesicle inactivates protein elongation factor 2 |
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What are the 3 organisms in which Shiga toxin is found?
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Shigella dysenteriae
enterohemorrhagic E. Coli (ETEC) E. coli in piglets |
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What is the general structure of Shiga toxin?
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5B:1A like cholera toxin
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True/False. Like cholera toxin, shiga toxin is a ribosylating enzyme.
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False. Inhibits protein synthesis by removing an adenine from the 28S rRNA
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What are the three components of the anthrax toxin?
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lethal factor- Zn++ dependent protease that induces cytokine release and cell death
edema factor- an AC protective antigen- binding unit for the 2 factors |
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How does anthrax toxin infect the host cell?
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PA binds to cell surface receptor and is cleaved by a host protease
PA is free to form multimers that can bind either EF or LF |
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What are the 2 ways membrane disrupting toxins lyse or damage cells? Give example of each.
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They act as membrane channels (alpha-2 toxin of S.Aureus)
They act as phospholipase (alpha-2 toxin of Clostridium perfingens). |
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True/False. The Lipid A component of endotoxin is associated with immunogenicity while O polysaccharide is associated with toxicity.
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False- reversed.
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What are 2 properties of endotoxin that are helpful for the host?
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Acts as a B cell activation factor (increase IgG and IgM)
activates macrophages |
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True/False. The structure of Lipid A is conserved amongst gram negative bacteria
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True.
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What are some clinical effects of endotoxin?
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fever
changes in white cell counts DIC hypotension shock death |
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General molecular mechanisms for clinical signs associated with endotoxic shock
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Triggering of monocytes/macrophages
cytokine production prostaglandin and leukotriene formation --> inflammation complement factors cause histamine release and vasodilation activation of clotting factor XII |
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Name 5 methods of avoiding humoral immunity
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Tolerance
Local blocking of immune forces Immunosuppression Hiding Antigenic variation |
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True/False. Tolerance involves a general dampening of the immune response.
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False. Only to a specific antigen.
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How does Bovine Viral Diarrhea Virus induce tolerance of the host?
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In utero infection leads to lack of Ab and T cell response throughout the cattle's lifetime.
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What are 3 methods of developing host tolerance for an organism?
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fetal exposure
high doses of antigen molecular mimicry |
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True/False. With host-adapted dermatophytes, relatively little inflammation and a chronic infection is established.
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True.
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The hyaluronic capsule of streptococci is what kind of host adaptive mechanism?
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Tolerance- molecular mimicry as it seems to be identical to the mammalian version in CT
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What are 2 methods that staphylococci locally block host immune forces?
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coagulase- surrounds itself with a fibrin layer derived from plasma
Protein A- binds to Fc portion of IgG. |
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Pseudomonas aeruginosa produces what enzyme that inactivates both C3b and C5a?
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elastase
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Which bacterial species produce IgA proteases?
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Neisseria
Haemophilus Streptococcus |
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True/False. One tactic to prevent antibody interaction is to make sufficient quantities of a released antigen so the released antigens bind most or all of the antibody.
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True
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What are 3 organisms that evade host humoral immunity by hiding in macrophages?
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Bucella
Listeria M. leprae |
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Name 2 organisms that evade host humoral immunity by hiding in non-phagocytic cells?
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Yersinia
Shigella |
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How do E. coli and Vibrio cholerae evade host humoral immunity?
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Lie in GI tract and cause little to no host cell destruction to sensitize lymphocytes and Ab
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Where does Brucella abortus hide to evade host humoral immunity?
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Mammary glands of cows
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What method of host humoral evasion does the spirochete Borrelia recurrentis employ?
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antigenic variation
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Which organism changes pili expression in order to evade host humoral immunity?
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Neisseria gonorrhea
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What are 5 ways pathogens evade host phagocytic defenses?
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Avoidance
Inhibition of engulfment Survival inside phagocytes Kill phagocytes Type III secretion system |
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What are some tissues that have relatively low phagocyte exposure?
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skin
lumen of glands |
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What are some anti-engulfment compounds and their pathogens?
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polysaccharide capsules- S. pneumoniae, H. Influenzae, Klebsiella pneumoniae
M protein of Streptococci Surface slime of pseudomonas aeruginosa O and Kantigen of E coli Protein A of S. aureus |
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What do the following organisms have in common?
Mycobacterium listeria salmonella shigella yersinia brucella legionella rickettsiae chlamydia |
Survive inside macrophages
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Which pathogens are engulfed by phagocytes and are resistant to lysosomal enzymes?
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mycobacteria leprae
brucella abortus coxiella burnetii histoplasma capsulatum |
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How do listeria, shigella, and rickettsia survive inside phagocytes?
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escape from phagosome and multiply in cytoplasm
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What are 3 organisms that kill the phagocyte that engulfs them?
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Staphylococci (hemolysins)
Streptococci (streptolysins) Pseudomonas |
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True/False. Type III secretion systems are found in an assortment of gram+ bacteria
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False. Gram-
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What are 3 things proteins injected by the type III secretion system accomplish?
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escape phagocytosis
limit the amount of cytokines the macrophage produces apoptosis. |
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How does Yersinia
inhibit phagocytosis inhibit cytokine production |
alter cytoskeleton
YopP interferes w/ MAPK cascade and TNF-alpha |
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What is the generalized life cycle of a bacteriophage?
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Adsorption
Penetration gene expression genome replication assembly release of progeny |
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What is the latent period?
The eclipse period? |
Time from initiation of infection to release of virions
Time to produce virions prior to release from host cells |
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Where does a bacteriophage inject its DNA?
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into the intramembrane space
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True/False. Some bacteriophages do not inject their DNA, but are engulfed by the bacterium.
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True. Filamentous phages.
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Which type of bacteriophage can enter a dormant stage and its DNA in host genome (prophage) and remains quiescent?
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Lysogenic phage
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Describe the adsorption and penetration process for tailed phages
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1) contraction of tail fibers to allow attachemnt of the base plate to the outer membrane
2) contraction of contractile sheath 3) passage of tail core through the cell wall 4) injection of phage DNA into intramembrane space 5) transport of DNA across cytoplasmic membrane |
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What are phages that insert their DNA into the bacterium by utlilizing the sex pilus?
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male-specific phages
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What are some strategies of phages to get their genes expressed in the host cell
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1) SPO1 uses its sigma factors to use host RNA polymerase
2) coliphage T7 encodes its own RNA polymerase that recognizes phage promoters |
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What is the strategy coliphage T7 uses to shut off host gene expression?
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Early gene product phosphorylates host RNA pol, later complexed and inactivated by a late gene product
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Define concatemer?
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Long stretch of DNA containing multiple copies of the phage genome as multiple copies of phage DNA are made at once
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What are the cos sites of lambda phage genome?
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Complementary ssDNA at either end of the linear genome that pair up after replication to form a circular chromosome for replication
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What is the benefit of circular DNA replication?
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DNA where the RNA primer binds is not replicated. Successive rounds would result in successfully shorter DNA molecules, but a rolling circle prevents this loss.
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How do linear phage genomes that don't circularize prevent genetic loss by replication?
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Ends of the genome contain identical sequences, so information missing at 3' end is present on the 5' end of the other daughter molecule.
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True/False. Phage assembly occurs without covalent modification of any of the components.
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True.
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What are 2 ways of releasing phage progeny from bacterial host?
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1) produce enzymes that destroy cell wall and cytoplasmic membrane
2) leak slowly without lysing the cell |
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What kind of phage causes a chronic, smoldering infection without lysing the host cell?
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pseudotemperate
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What is a lysogen?
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A cell bearing a prophage in its genome
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How might lysogeny by a lambda phage be beneficial to the host cell?
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It is immune to subsequent infection by lambda phages- imparts heteroimmunity
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How does host cell damage induce the lytic phase of a lysogenized phage?
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Activation of SOS
RecA promotes autocleavage of the cI repressor, ending lysogeny |
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How would plaques of temperate phages compare to lytic plaques?
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temperate are turbid
lytic phages form clear plaques |
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True/False. Some antibiotics can lead to phage induction.
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True.
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Determinants of bacterial virulence may be encoded by phages and plasmids as well as bacterial chromosome.
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True.
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True/False. Antibiotic-resistance carrying plasmids may be transmitted between gram - and gram + bacteria.
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True.
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What is it called when DNA from one bacterium is transmitted to another by phage?
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transduction
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What is an integron?
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Genetic element having an integrase gene, promoter element and attachment site. Often results in a series of genes in tandem with multiple antibiotic resistance genes and flanked by transposons.
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What is the difference between prophylactic and metaphylactic?
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metaphylactic is given during the incubation period of infection, prophylactic is to prevent infection.
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True/False. Not all members of the normal flora can cause disease.
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False.
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Name some benefits of normal flora?
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protection from more pathogenic bacteria by competition of bacteriocidins
nutritional- vitamin K low-level stimulation of antibodies develop of certain tissues (cecum) |
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How does stress influence the makeup of the natural flora?
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decrease anaerobic
increase gram - |
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What is the number 1 organism of the skin flora?
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coagulase negative staphylococci
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True/False. The respiratory tract is normally heavily colonized, including upper and lower airways.
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False. The lower respiratory tract is relatively free of microorganisms
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What are 2 normal floral organisms that can survive the stomach?
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lactobaccilus
helicobactor pylori |
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True/False. The proximal small intestin is not heavily colonized with bacteria.
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True. Likely due to peristalsis.
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True/False. Protozoa and bacteria represent the same dry weight in the rumen.
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True.
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About how much of the rumen bacteria are cellulolytic?
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5%
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What is the principle cellulolytic bacteria of the rumen?
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Bacteroides succinogenes
has cell-bound cellulase |
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How do bacteria help regulate the pH and redox potential of the rumen?
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Methanogens convert H2 (in equilibrium with H+) and CO2 to methane
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alpha hemolysin
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creates pore in host cell membrane
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beta hemolysin
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chews up cell surface
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delta hemolysin
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detergent-like molecule
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What does staphylokinase do?
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lyses fibrin
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