MIC 205: Final Exam
54 Cards in this Set
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Why is immersion oil used when using a microscope?
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It gives better resolution because it straightens out light rays and focuses them on the organism.
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What is the difference between a simple and differential stain?
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Simple stain uses only one dye. Used to show bacterial morphology. Differential stain uses more than one dye. Seperates (differentiates) organisms.
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What is a dye that can be used as a simple stain?
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Methylene blue
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Is a gram stain differential or simple?
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Differential
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Is a Schaeffer-Fulton endospore stain differential or simple?
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Differential
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Is an acid fast stain simple or differential?
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Differential
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What color are endospores and vegetative cells when stained with a Schaeffer- Fulton stain?
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Vegetative- red/pink
Endospores- green
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What genera form endospores?
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Gram- positive rods. Bacillus and Clostridium
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What biochemical test do we use to differentiate between Bacillus (aerobe) and Clostridium (anaerobe) since both are Gram positive rods?
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We can put the organism in a thioglycollate broth. If it grows in the bottom it is an anaerobe and if it grows close to the top it is and aerobe.
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How do endospores benefit the bacteria that produce them?
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It allows them to withstand harsh environments that would kill them. Can withstand radiation, drying, and chemicals.
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What is the difference between Gram positive and Gram negative cell walls? How does this affect the way they will stain on a Gram stain?
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Gram + cell wall has thick layer of petidoglycan and techoic acid. Gram - cell wall has thin layer of peptidoglycan surrounded by thick layer of lipopolysaccharides. Has lipid A portion (endotoxin). The thick layer of peptidoglycan allows the Gram + cell to retain the first dye when washe…
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What color is a Gram+ organism?
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Purple
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What color is a Gram- organism?
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Pink
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What does Staphylococcus look like when Gram stained? Color and morphology?
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Purple cocci in clusters
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What does Streptococcus look like when Gram stained? Color and morphology?
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Purple cocci in chains
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What does E. Coli look like when Gram stained? Color and morphology?
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Pink rods
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What do Clostridium and Bacillus look like when Gram stained? Color and morphology?
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Purple rods
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What does Neisseria look like when Gram satined? Color and morphology?
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Pink cocci
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Name an organinsm that produces a capsule.
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Enterobacter
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How do capsules benefit bacteria?
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Helps bacteria resist phagocytosis. Can be metabolized as energy source. Helps it attach to various objects (skin mucous membranes and hard surfaces such as door knobs or toilet seat)
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Give the genus name of an acid-fast organism.
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Mycobacterium
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Why don't acid fast organisms stain well with Gram stain?
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They have high contents of mycolic acid that don't allow the dye to penetrate the cell wall.
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What color are acid fast organisms when acid fast stained?
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Red
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What is the name of the lipid in the acid fast organisms cell wall?
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Mycolic acid
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What kind of an environment does a Gas Pak jar create and what kind of organism grows well in it?
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A Gas Pak jar creates an anaerobic environment and an organism that only grows in the complete abscence of oxygen will grow in it.
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What kind of environment does a candle jar create and what kind of organism grows well in it?
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A candle jar creates a microaerophilic environment. Only organisms that grow in low levels of oxygen and raised CO2 will grow in it.
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Define aerobic organism.
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An organism that grows in an environment where oxygen is readily available.
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Define microaerophilic organism.
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An organism that grows in an environment where the oxygen is reduced and the CO2 is increased.
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What is a facultative anaerobe?
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Organism that can grow in the presence of oxygen or without oxygen.
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What is an obligate anaerobe?
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Cannot grow in the presence of oxygen.
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Where would an aerobic organism, a microaerophilic organism, a facultative anaerobe, and an obligate anaerobe grow in a thioglycollate broth?
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Aerobic organism- Top
Microaerophilic organism- Middle
Facultative anaerobe- Throughout
Obligate anaerobe- Bottom
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How would an aerobic organism, a microaerophilic organism, a facultative anaerobe, and an obligate anaerobe grow in a candle jar? A Gas Pak jar?
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-Candle jar-
Aerobic organism- very little
Microaerophilic organism- very well
Facultative anaerobe- very well
Obligate anaerobe- none
-Gas Pak-
Aerobic organism- none
Microaerophilic organism- very little
Facultative anaerobe- very well
Obligate anaerobe- very…
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How do catalase reactions correlate with an organisms ability to tolerate oxygen?
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Organisms that produce catalase are able to break down toxic froms of oxygen and their intermediate products. Without catalase they will die when exposed to our atmoshpere.
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How would you use catalase to differentiate Staphylococcus and Streptococcus? Bacillus and Clostridium?
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You take the organism and put some of it on a clean slide. You then put a drop of H2O2 (hydrogen peroxide) on the organism and if it produces bubbles it mean that the organism has catalase that breaks the H2O2 into water and oxygen. Staphylococcus would be catalase positive and would prod…
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What is a viral plaque?
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A viral plaque is the clearing formed when bacteria growing on media are exposed to a virus and the virus lyses the bacteria.
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What factors influence the results of the Kirby-Bauer antibiotic sensitivity test?
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There are several factors including: antibiotic stability, diffusion rate of antibiotic, pH of culture medium, depth of culture medium, inoculum density, incubation time and temperature, antibiotic concentration.
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What is the advantage of doing an MIC test versus the Kirby-Bauer test?
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The MIC test is more accurate. It will tell you the lowest dose needed of the given antibiotic to treat the organism. The Kirby-Bauer test only tells you if the organism is sensitive to the anitbiotic.
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Name one way that bacteria give drug-resistance genes to each other.
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Conjugation
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How did E. Coli gain the flourescence gene in the bioluminescence experiment?
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Through transformation. The bacteria picked up the gene through a plasmid from the environment.
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What media is used to grow fungi?
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Sabouraud Dextrose agar
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Why do most bacteria not grow on Sabouraud Dextrose agar?
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Because the pH is too low.
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What is the difference between a conidiospre and sporangiospore?
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Sporangiospores are produced at the ends of aerial hyphae called sporangiosphores. They are contained in a saclike structure called a sporangium. Conidiospores are formed on hyphae called conidiosphores.
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What stain or dye is used to make mold spores more visible?
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Methylene blue
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What is selective media?
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Selective media is one that allows certain organisms to grow while suppressing the growth of others.
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What is differential media?
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Media that can cause two organisms growing on it to appear differently.
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What ingredients are in MacConkey agar?
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Bile salts and dyes make it selective for Gram negative organisms. Lactose makes it differential by showing whether it metabolizes lactose.
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What ingredients are in CNA agar?
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Antibiotics make it selective for Gram positive organisms. Blood cells determine whether it has hemolysin or not.
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What ingredients are in Mannitol Salt Agar?
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Salt makes it selective for Staphylococcus. Mannitol makes it differential between two Staphylococcus.
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What is the difference in appearance of media that contains a lactose fermenter versus media that contains a non lactose fermenter on MacConkey agar?
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The media will usually turn bright pink on a lactose fermenter if not the organism will.
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What does Mannitol Salt Agar look like when the organism growing on it ferments mannitol?
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It turns yellow
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What makes blood agar (CNA) differential?
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It is differential because of the blood cells it contains. What level of hemolysis the organism causes allows them to be classed as alpha, beta, or gamma hemolytic organisms.
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What does Alpha Hemolysis look like?
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Partial (incomplete) hemolysis with a somewhat green tint to the media.
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What does Beta Hemolysis look like?
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Complete hemolysis causing the media to go clear.
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What does Gamma Hemolysis look like?
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No hemolysis and no alteration of the media.
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MIC 205: Final Exam