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59 Cards in this Set
- Front
- Back
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What is a genome? What are metagenomes?
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sum total of an organism's genetic info; collection of DNA sequences and enables identification of non-cultruable microbes
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What is spontaneous generation? What was Lazzaro Spallanzani’s contribution to disproving this?
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life arise from non-living matter; he demonstrated cell fission when he watched a single microbe grow in size until it split into two (sealed flask of meat broth sterilized by boiling failed to grown microbes)
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How did Louis Pasteur finally disprove the theory of spontaneous generation?
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heated growth medium; swan neck design remained free of microbial growth for many years but when flask tilted to enable contact of broth with microbe-containing dust, growth occurred immediately
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Describe Robert Koch’s contributions to microbiology, specifically:
a. Germ Theory of Disease – What is this? b. Describe the theory behind pure culture – how can one grow microbial cultures? What is the difference between growth on liquid vs. solid media? c. Koch’s Postulates: What are these? What is their significance? |
a) many disease are caused by microbes
b) isolate a single bacteria from a mixed culture; c) causative link between an infectious agent and a disease; microbe absent from healthy individuals, microbe isolated from the diseased host and grown in pure culture, when microbe introduced in healthy indv., same disease occur, same stain of microbe is obtained from the newly diseased host |
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What is the principle of immunization? What is vaccination and how does this relate to immunization?
What were Edward Jenner’s and Pasteur’s contributions to this field? |
stimulation of an immune response by deliberate inoculation with an attenuated pathogen; rely on attenuated virus/bacteria; cowpox vaccination to protect against smallpox; first to recognize the significance of attenuation and devised rabies vaccine with multiple heat treatment
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What is meant by aseptic technique? What were Semmelweis’ & Lister’s contribution to this?
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something that kills microbes; decline in childbed fever with used of antiseptic; employed use of antiseptic agents to treat wounds and surgical treatments
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What is the key rule of chemotherapy? What are antibiotics? What did Alexander Fleming do and how did
he do it? |
cure disease without harming healthy cells; kill microbes internally; discovery of penicillin; cultured Staphylcoccus and found one plate was contaminated with a mold (penicillin) which killed bacteria
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What was Sergei Winogradski’s contribution to microbiology? What is enrichment culture? What are
endosymbionts? |
first to study microbes in natural habitat; use of selective growth media that support certain classes of microbial metabolism while excluding others; association between microbe and other organism (ex. E.coli and intestine)
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What was Carl Woese’s contribution to the classification of life on Earth? What are Archaea? What is the
endosymbiont theory? |
used rRNA to show archaea is distinct from bacteria and eukaryotes; prokaryotes that have some molecular features of eukaryotes and inhabit extreme environments on earth; internalization of certain bacterial cells to form chloroplast and mitochondria
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How did electron microscopy and ultracentrifugation advance microbiology in the 20th century? How did
microbiology contribute to recombinant DNA technology and its application to medicine and industry? |
detailed visualization of cell structures; isolation of subcellular structures and characterization of their functions; restriction enzymes and biotechnology
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What are the disciplines of microbiology?
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bacteriology, mycology, phycology, virology, protozoology (non-pathogenic), parisitology (pathogenic), immunology, epidemiology, and chemotherapy
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In microscopy, what is meant by resolution and detection? How do these differ?
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limits the size of the object visible to the unaided eye (min. distance at which two objects can be separated); the ability to determine the presence of an object; detection requires magnification
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What are the size limits for light
microscopy, electron microscopy, atomic force microscopy, and X‐Ray crystallography? |
0.2 um; 0.01 um; 1 nm; 1 nm
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What are the factors that help to improve resolution of an object when using a light microscope?
How/why does immersion oil improve resolution? What is an Airy disk? What do these arise from? |
optimal light, refraction (bending of light), magnification, numerical aperature, shorter wavelength, and high contrast; it has refractive index comparable to glass and allows more light to enter objective lens
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What is an Airy disk? What do these arise from?
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central sphere of intensity form surrounded by concentric spheres of light and dark
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On a compound microscope, what is the function of the condenser and diaphragm? What is meant by “depth of field” and “parfocal”? How is total magnification calculated?
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consist of one or more lenses that focus parallel light rays from the light source onto a small area of the slide; vary the diameter of the light column;object in focus remains focus when lens rotated ; ocular lens x objective lens
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What is the purpose of staining a microbial sample for observation under a microscope? What is the
difference between a simple stain & differential stain? What are examples of differential stains? What is a counterstain? |
enhances contrast and resolution; differential stains one type of cell but not another; gram stain, acid fast stain, spore stain, and negative stain; allows visualization of gram-negative material
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What are the types of light microscopy? Which type is typically used for viewing cells in their natural state?
Which type is used for viewing structures unresolvable by usual light microscopy such a flagellum? Three dimensional images are provided by this type of microscopy. What can one do with fluorescence microscopy? |
darkfield, phase-contrast, interference, and fluorescence; phase-contrast; darkfield; interference; stain specimen with fluorophore and label specific parts
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What is the difference between scanning and transmission electron microscopy? How does atomic force microscopy differ from electron microscopy? What does analysis by X‐Ray crystallography determine? Is the latter a method of microscopy?
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in TEM electrons are transmitted through the specimen as in light microscope and in SEM electron beams scan across the surface of the specimen and are reflected to reveal the contours of its 3D surface; produces 3D image resolving power and in electron, electrons are focused using magnets; 3D structure of molecules based on x-ray diffraction; yes
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Why is it important to study microbial growth? What is required for growth? What is complex media? What
is defined medium? |
Understanding how to isolate, culture, and grow microbes
allows us to exploit them for different purposes; Essential nutrients, macronutrients, and micronutrients; contains one or more complex nutrients of undefined composition; the exact chemical composition is known |
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How is a microbe defined as a heterotroph or autotroph? What are the two types based on energy source and how is energy obtained by each? Describe the following in terms of carbon & energy source:
chemoautotroph, chemoheterotroph, photoautotroph, and photoheterotroph. What is a chemolithotroph? In what forms is energy stored in microbes? |
heterotroph: breakdown of complex organic cpds, and autotroph: breakdown on inorganic cpds; Phototroph: absorb & convert light energy to chemical energy, and Chemotroph: obtain energy
from oxidation reduction reactions; chemical, carbon sources, and light carbon source; organisms that use light for photosynthesis; ATP or in the production of H+ gradients |
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What is nitrogen fixation, nitrification, and denitrification? What types of nitrogen‐fixing bacteria are there?
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N2 gas enters the soil as nitrogen‐fixing bacteria convert it to NH4, NH4 to NO3-, and NO3 to N2; symbiont
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List and describe the active transport mechanisms of nutrient transport in microbes. Why must they generally use active transport mechanisms? What is the non‐energy using transport mechanism called? How are these nutrients transported?
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Symport and Antiport: Gradient of one molecule transports another, Transports material against its gradient, and Electron transport creates Proton‐Motive Force, Group Translocation: Uses ATP energy to pass material into cell, Modifies material as it enters cell and gradient is maintained, pushing material into cell,and Sequestering iron from the environment: bacteria
produce & secrete siderophores for this function, ABC Transporters: Use ATP energy to pass material into cell, Transport material against gradient, Some cellular nutrients enter by facilitated diffusion (passive); Due to typically low nutrient conditions in the environment, microbes must concentrate nutrients inside the cell |
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What is the dilution streaking method? What is it used for? What is the purpose? What is the spread plate method and how is this executed? What is meant by “viable but non‐culturable” and axenic culture?
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mechanical dilution of cells as they
are spread on the plate surface; goal |
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How does growth of bacteria on rich media compare to growth on minimal media? Why is there a difference? What is enrichment culture? Why would one employ this latter technique? How is selective media different from differential media? What is the purpose of each?
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rich: possesses pre‐formed nutrients the cells can readily assimilate and minimal: cells must synthesize all required molecules from simpler building blocks; enhancement of the growth of microbes present in small numbers and Add components to media to favor their growth; selective: contains chemical
components that inhibit certain bacteria, favors the growth of others and differential: can visualize metabolic differences between Blood agar is differential; bacterial types; |
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List and briefly describe different ways to enumerate bacteria (categorize as a direct, indirect, or viable count method). What is meant by direct count, indirect count and viable count? How do these differ?
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Direct count methods: obtain actual cell concentrations- Petroff‐Hauser chamber: count cells under microscope, Fluorescence microscopy: dyes distinguish between live/dead cells, and Coulter counter or cell sorter; Indirect count methods: employ liquid culture; counts live & dead cells- Dry weight of culture samples, Biochemical: analyze protein or DNA concentration of samples, and Optical Density: measure light absorbance by culture; Viable count methods- Spread plate or Pour plate method: count colonies on/in plates;
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What is generation time? Why is growth data from a bacterial culture best represented using the log scale? What is the equation for determining the number of generations? What is the mean growth rate constant (k)
represent? How does growth in pure culture differ from growth of a microbe in nature? |
time for cell to divide; linear growth; n = log10 (Nt/N0)/0.301; rate of exponential growth;
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Draw a hypothetical growth curve for a bacterial culture growing in liquid medium and indicate the different stages of growth. What is occurring during each stage?
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Lag Phase: cells transferred to
fresh media; cells adjust to new surroundings, initiate gene expression – no cell division occurs, Log phase: exponential, or log growth, Stationery Phase: in late log phase, generation time slows, quorum sensing occurs |
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How does growth in batch culture differ from growth in fed‐batch culture? What is continuous culture? Draw a basic diagram showing how continuous culture would be prepared. What effect would increasing the rate of nutrient addition have?
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closed system; growth of
cells in a culture flask without any manipulations or additions to the culture, closed system; growth of cells in a culture flask without any manipulations or additions to the culture; culture system that allows for perpetual growth of cells at specific cell densities ( Continuous addition of fresh culture medium and continuous siphoning of culture fluid); Increasing addition of nutrient (dilution rate), increases cell density |
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What is a biofilm and how do they form? What is meant by quorum sensing?
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surface‐attached communities, Biofilm formation critical roles in pathogenesis, infections due to medical apparati, environmental issues; Cellular communication (quorum sensing) triggers formation of exopolysaccharide from the microcolony forming an extracellular
matrix of entrapped organic & inorganic molecules |
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What is cellular differentiation? What is an endospore and what are the features of a spore? What are two major taxonomic groups among bacteria that form spores? What are heterocysts? What microbes form
these? What happens to Myxococcus under conditions of nutrient limitation? How do many members of the Actinomyces group, e.g., Streptomyces, Nocardia, grow on solid media? What organism do they resemble? |
Under conditions of environmental stress certain bacterial
types will differentiate, generating different structural forms; Nutrient limitation stimulates genetic changes that initiate sporulation |
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What is an extremophile?
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Microbes that live and thrive outside these ranges
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How does temperature affect cellular function? What is the Arrhenius effect? What are the different temperature classifications of microbes and their temperature ranges? What does the heat shock response refer to?
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affects the molecular motion of molecules, thus entire physiology of microbe is impacted by temperature
changes ( Membrane fluidity, transport, DNA/RNA stability, enzyme structure & function); growth rate doubles for every 10°C rise in temp; breaks down beyond upper/lower limits of growth; High temp: protein denaturation and Low temp: decreases in protein activity & membrane fluidity; Psychrophiles ~ 0–20'C, Mesophiles ~ 15–45'C, Thermophiles ~ 40–80'C, and Hyperthermophiles ~ 65–121'C; activation of stress response genes, expres‐sing proteins that stabilize protein shape & others that change membrane lipid composition. |
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What are barophiles or piezophiles?
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microbes are adapted to grow at high
pressures |
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What is meant by water activity? How does this relate to osmolarity? During osmotic stress how does the cell respond to hypertonic solution? to hypotonic solution? What are halophiles?
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measure of water availability; ratio of solution’s vapor pressure relative to pure water; is equivalent to the total solute concentration; in hypertonic media, cells import or synthesize compatible
solutes and in hypotonic media, pressure sensitive (mechanosensitive) channels leak solutes out of cells; require 10‐20% NaCl; aw = 0.75 |
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How do extremes of pH (high or low) affect microbes? How does intracellular pH differ from extracellular pH? How can organic acids affect intracellular pH? What classifies microbes as acidophilic, alkaliphilic, or
neutralophilic? How do alkaliphiles maintain pH homeostasis? What basic mechanisms of maintaining pH homeostasis in neutralophiles? |
Extremes of either ion affect protonation of amino‐ & carboxylgroups
in cellular proteins, and thereby alter their charges |
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How is oxygen utilized by aerobic microbes? How is oxygen damaging, even to aerobic microbes? List and
describe the types of microbial responses to oxygen or lack of oxygen. What are protective mechanisms microbes have to minimize oxygen damage. How are anaerobes cultured? |
Special enzymes protect against potential damage by ROS’s: Superoxide dismutase (SOD) –
neutralize superoxide radicals Catalase (detoxifies H2O2) Peroxidase (detoxifies H2O2); Obviously culturing anaerobes requires procedures to remove oxygen from the growth environment: Reducing media, Anaerobe jar; pellets release H2, CO2 & catalyst that removes O2, and O2 removal by purging culture medium with N2 |
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What happens to cells when under nutrient deprivation? What are oligotrophs?
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Starvation response p by cells occurs when nutrients decline;
purpose of response is to gear itself to find new nourishment (Numerous genes expressed; growth slows; progeny cells become smaller, Increased concentrations of signal molecules, and Transport systems for potential nutrients are produced; synthesis & storage of glycogen. Some species yield changes in colony formation); microbes that can grow very well under low organic substrate amounts |
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In terms of controlling microbial growth, describe the differences between: sterilization, disinfection,
antisepsis, and sanitation? How do bactericidal agents differ from bacteriostatic agents? What is a germicide? |
Sterilization: destruction of all living cells, spores, viruses from an
object, Disinfection: reduction of disease producing organisms from inanimate objects, Antisepsis: reduction of microbial numbers from living tissues, and Sanitation: related to disinfection; reduction of microbial populations to safe levels; ability to kill cell and inhibiting growth; chemical kills pathogenic microbes & viruses |
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What is the decimal reduction time, or D‐value? What factors affect the D‐value of an antimicrobial agent?
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Equals length of time for agent
to kill 90% of the population; microbial load; agent concentration; time of exposure; population composition |
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Describe physical agents that control microbial growth and the mechanisms by which they act. Which is most
effective in killing spores? |
High temperature & pressure: moist g p p heat is the key to killing cells
as water can penetrate cells, Pasteurization: for food & beverages; various time/temp combinations to kill Coxiella burnetii, most heat resistant non‐sporeformer, Cold temperature: microbes grow more slowly die slower, Irradiation: bombard with high energy radiation; causes DNA damage, killing cells. Used to sterilize food & non‐biologicals, Deinococcus radiodurans: microbe with the highest ability to resist radiation; accumulates Mn2+ to remove free radicals; High temperature & pressure |
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What is the phenol coefficient test? What is this used for and how is it carried out? What is the disk diffusion method? How does this method evaluate antimicrobial agents?
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phenol is the benchmark
against which other disinfectants are evaluated (Phenolic compounds are useful as disinfectants since they denature proteins & remain active on surfaces after application), inoculate fixed amounts of culture to dilutions of test chemical, a timed intervals, withdraw samples from dilution tubes & transfer to fresh broth (not containing disinfectant); incubate, and highest dilution tube of disinfectant that kills all bacteria in a test after 10 minutes exposure & leaves survivors after 5 minutes exposure = maximum effective dilution (MED); Confluent growth of bacteria on plate, place disks soaked in disinfectant on plate. Look for zones of inhibition |
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List examples of common commercial disinfectants and briefly describe how they act on microbes. Do microbes generally become resistant to these agents? Why or why not? What are antibiotics? Where do they originate from?
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Ethanol, iodine, chlorine: damage proteins, lipids, DNA, Detergents: solubilize membranes, Gases: for plastics; ethylene oxide; No, bc most disinfectants have multiple cellular targets, thus cellular resistance not likely; produced by microbes to kill other microbes
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What are probiotics? What is the idea behind their mode of action in controlling microbial growth?
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exploit microbial competition to regulate or control populations; eating yogurt;
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What are the features all prokaryotic cells possess? Which are variable characteristics?
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DNA contained in a nucleoid region, cell (plasma) membrane, Ribosomes, proteins, RNA, Most have a cell; flagella, pili, plasmids, capsule/slime, and inclusions
wall |
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What is the role of hopanoids in prokaryotic cell membranes? What are hopanoids analogous to in animal cell membranes? How do the phospholipids of Mycobacteria species and Archaea differ from typical prokaryotes?
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lipid molecules between
phospholipids; reinforce the bacterial membrane; mycolic acids (up to 50‐60 carbon atoms in length) and terpenoid compounds linked to glycerol by ether linkages |
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Describe the structure of a prokaryotic cell wall
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The cell wall provides protection, confers shape, and helps to withstand changes in osmotic pressure, It is a single molecule that surrounds
the cell membrane and is permeable to ions & small molecule, and composed of peptidoglycan |
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Compare and contrast
the differences/similarities in the outer membrane/cell wall structure of Gram‐negative and Gram‐positive bacteria, respectively |
G-: thin cell wall, bridged to the
outer membrane via the murein lipoprotein, posses complex outer membrane ( Contain proteins not found in the inner cell membrane, and Porins: permit entry of sugars and peptides; cell controls expression of porins as dictated by the environment), The LPS layer can act as an endotoxin; when the microbe dies, the LPS layer is released and can overstimulate host defenses, causing shock, and Periplasm: between inner membrane & outer membrane ( Contains unique enzymes and nutrient transporters) G+: thick cell wall; multiple peptidoglycan layers penetrated w/teichoic acids,Teichoic acids penetrate the peptidoglycan layers helping to reinforce it, S‐Layer: surface layer comprised of an ordered array of protein or glycoprotein; is porous, Mycobacteria: complex cell envelope containing mycolic acids linked to sugars and phenolic glycolipids – produces a waxy envelope ( Provides protection against host defenses & is the basis for acid fast staining) |
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What is the nucleoid? How is prokaryotic DNA compacted inside the cell? What proteins and/or enzymes help to compact the DNA?
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The DNA is organized in loops; supercoiling; gyrase
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How does cell division occur in a prokaryotic cell? Where does DNA replication begin? What is septation?
How does this differ between rod‐shaped cells and cocci? What is a cytoskeleton? How does this function in bacteria? |
DNA replicates bidirectionally (requires 2 replisomes, Can begin next replication
before cell divides, and Terminator sequence ends replication); ORI sites; daughter cell divide at equator into two furrow; cocci: new cell wall synthesis at equator yields furrow; 2 cell walls synthesized between cells and rods: cell division requires elongation of envelope before septation (FtsZ); functions to provide shape & form to a cell as well as provide protection & other functions; FtsZ: Forms a “Z ring” essential for cell septation, MreB Protein:Forms a coil inside rodshaped cells, and CreS: Curves inner side of crescent‐shaped bacteria |
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What are specialized structures of phototrophic bacteria? What are their functions? What are intracellular inclusions? List and describe the different types found in bacteria.
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Thylakoids: extensive foldings of the inner cell membrane; packed with photosynthetic
components and Carboxysomes: protein‐covered bodies containing CO2 fixation enzymes; Metachromatic granules (volutin): inorganic phosphate stores, Polysaccharide granules: glycogen/ starch, Lipid inclusions: PHB, Sulfur granules: from oxidation of H2S, Magnetosomes: crystals of magnetite (Fe3O4) in magnetotactic bacteria, and Gas vacuoles: maintain buoyancy in aquatic environment |
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What are the functions of pili/fimbriae? What is a sex pilus?
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cells adhere to surfaces; attachment to appropriate recipient cell for transfer of DNA
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How does bacterial motion occur via a flagellum (or flagella)? What is chemotaxis? What are the different flagellar arrangements a bacterial cell may possess?
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rotary flagella; Movements are toward attractants or away from repellents; Counterclockwise flagellar
rotation propels the cell forward and clockwise motion stops motion causing tumbling. |
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What is the glycocalyx? How does a slime layer differ from a capsule? What does a capsule provide?
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general term for polysaccharide/protein secretions surrounding cell; a viscous, gelatinous polymer; loosely attached and not well organized and firmly attached & organized, virulence
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Write a brief description of the roles microorganisms have in the following areas: (a) ecology, (b) public health, (c) genetics, and (d) biotechnology.
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a) possess a diverse array of
metabolic capabilities and nutrient cycling & decomposition; b) cause disease, vaccination, antibiotics, and viruses; c) genetic code & protein synthesis, DNA technologies, and Gene regulation; d) agricultural, textiles, medicine, food industry, chemical industry, energy |
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How do you define a microbe? What are exceptions to this definition? Are microbes always not visible to
the naked eye? |
need a microscope to see; Viruses: are acellular; exploit
host cells to replicate, Microbial communities: biofilms, certain algae/fungi, and Super‐sized cells |
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What are the six major groups studied by microbiologists? How do these latter groups fit into the three domains of life? Which are prokaryotic and eukaryotic?
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bacteria, archaea, fungi, virus, algae, and protist; bacteria-prokaryote, archaea-prokaryote, and eukarya-eukaryotes
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What are some of the basic differences between
prokaryotic and eukaryotic cells? |
non-membrane bound nucleoid
region; 1-10 μm diameter, Lack organelles; has cytoskeleton elements, and Domains Eubacteria & Archaea; Chromosomes: located in a membrane bound nucleus, 10-100 μm diameter, Organelles of specific form & function, Possess fully developed cytoskeleton, and Domain Eukarya |
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Domain
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Eukaryak
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