Microbiology 202 Quiz 3 – Flashcards
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| Staphylococcus and Micrococcus are both in which family? |
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| Micrococcaceae |
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| Where are staphylococcus and micrococcus most likely to be found? |
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| on the human body, especially skin. |
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| what are the 6 common traits of staphylococcus and micrococcus ? |
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| gram positive, growth in tetrads(micrococcus) or clusters (staphylococcus), no endospores, tolerate salty conditions. both are catalase positive. |
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| How do micrococcus cells carry out respiration? |
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| strict aerobe |
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| how do staphylococcus cells carry out respiration? |
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| facultative |
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| Which type of staph cell causes TSS? |
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| staphylococcus aureus |
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| what is the most common type of staph? |
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| staphylococcus epidermidis |
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| Which type of Staph sometimes causes a urinary tract infection? |
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| staph sarophyticus |
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| what type of agar is mannitol agar? |
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| selective: high salt concentration that selects staph and micro..but also differential because it contains pH indicator phenol red |
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| What's the best way to tell the difference between micrococcus and staphylococcus? |
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| what they do in the absence of oxygen...micrococcus won't ferment mannitol but staphylococcus would |
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| which staph cannot ferment mannitol? |
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| s. epidermidis |
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| What is the purpose of the novobicin assay, and how does it work? |
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| to further differentiate staph strains....antibiotic resistance test. |
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| what is the only staph strain that is resistant to novobiocin? |
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| s. saprophyticus |
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| If a bacteria is sensitive to an antibiotic, what is the diameter of "no growth" that will occur? |
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| 18mm |
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| How does S. aureus cause clotting? |
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| the bacteria produces coagulase, which interacts with fibronogen, which is an insoluble protein and clogs circulatory system,. |
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| how do we detect coagulase? |
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| bead connecting assay |
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| can m. luteus ferment glucose? |
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| no |
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| which strept does not produce catalase? |
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| streptococcus enterococcus |
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| are pseudomonas pathogenic? |
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| no |
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| which type of gram negative bacteria have flagella? |
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| pseudomonas |
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| are pseudomonas gram positive or negative? |
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| gram negative rods (bacilli) |
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| which type of gram negative bacteria produce pigments that are water soluble? |
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| psuedomonas |
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| are all psuedomonas strike aerobes? |
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| no--some can live anaerobically if nitrate is available. |
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| can pseudomonas carry out fermentation? |
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| no...strictly electron transport chain |
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| Can psuedomonas oxidize glucose? |
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| yes, but only under aerobic conditions |
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| what is the O/F assay? |
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| seeks to identify pseudomonas through the oxidation of glucose --> production of organic acids in aerobic environment |
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| How are Enterics defined? |
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| gram negative rods, all facultative aerobes, do not produce spores, ...found in large intestines, ferment glucose to produce acid and gas |
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| All enterics ferment glucose, but do all enteric ferment lactose? |
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| no |
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| what is the difference between coliform and noncoliform? |
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| types of enteric that CAN ferment lactose are called coliforms. |
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| What are three types of coliform enterics? |
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| E. coli, enterobacter, klebsiella, citrobacter |
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| What are types of noncolifrom enterics? |
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| proteus, salmonella, shigella, serratia, providencia |
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| are MaConkey plates differential or selective? |
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| both....selective because it only allows the growth of gram negative bacteria and differential because it has a pH indicator to distinguish coliforms from non coliforms |
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| On Maconkey agar, how can you tell is an enteric can ferment lactose? |
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| the agar around the bacteria will be bright red for a positive reaction |
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| what kind of indicator is used in the MaConkey agar assay for enterics? |
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| neutral red |
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| What is the difference between EMB plates and MaConkey agar plates? |
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| EMB is more selective than MaConkey |
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| what is considered a positive reaction for lactose fermentation on EMB agar? |
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| colonies will become dark red //purple to black..therfore we can assume these are coliform species |
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| if a bacteria has a green metallic sheen on EMB agar, what can we say bout it? |
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| enteric, coliform, REALLY FERMENTS, and probably e. coli |
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| what is the purpose of the methyl red assay? |
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| to differentiate between bacterial species that produce a small amount of organic acids and high concentration |
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| What is the Voges-Proskaueh assay? |
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| test for presence of acetoin |
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| how does the methyl red indicator work? |
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| turns red at extremely high organic acid concentratoin..turns orange at pH 4.6-5.6 and turns yellow around neutral pH |
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| what is the purpose of the citrate assay? |
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| to detect the use of citrate as carbon source |
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| Is Simmons Citrate agar differential or selective? |
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| selective for gram negative...differential in that it changes color for which type of carbon source used. |
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| what is a positive reaction for citrate assay? |
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| if there is macroscopic evidence of cell growth and if the medium is deep or royal blue in color, this is considered a positive reaction |
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| Would e. coli be able to survive on citrate alone? |
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| no...it wouldn't. if it was a positive reaction, it probably would be E. aerogenes. |
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| Which species is noted for its ability to produce urease? |
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| proteus |
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| does urease production increase or decrease pH? |
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| increase |
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| what is a positive reaction for the urease assay? |
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| if the broth turns bright pink within 24 hours, it has the ability to produce urease |
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| what is the positive reaction for the H2S assay? |
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| if the SIM agar turns black |
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| what does the indole production assay test for? |
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| the breakdown of the amino acid tryptophan |
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| Why do we add Kovac's reagent to the broth? |
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| it will combine with indole present to form a red compound |
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| what are the approx. lengths of flagella? |
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| 30 to 40 nanometers |
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| Do most enterics have flagella? |
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| yes except klebsiella and shigella |
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| what's the difference between bacterial strains and and species? |
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| strains: derived from a single colony...there are thousands of strains within one species |
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| What is the name of the guide used to identify ID of enterics? |
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| Enterotube Interpretation Guide |
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| What do we look for to indicate fecal contaminated water? |
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| coliforms |
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| What is the presumptive test? |
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| a series of dilutiions to assess if there are coiforms present in large to trace amounts of water. |
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| coliforms are an example of an ______ species |
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| indicator |
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| What is the confirmed test? |
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| uses EMB agar to determine if the results from the presumptive test actually came from coliforms |
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| What is the completed test when testing for fecal contamination? |
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| a colony is picked from the confirmed test EMB plate and grown up again in another lactose broth with a Durham tube. it tests to see if it is positive for gas from lactose and gram negative rod |
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| How do we determine if E. coli and Salmonella are in meat? |
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| selection through HE agar...selective for gram negative...high bile salts so there is high selection for salmonella and shigella |
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| how is HE agar differential? |
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| differentiates between "lactose or sucrose fermenters" and "nonfermenters" |
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| what is a positive result in the HE agar assay? |
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| if the colonies and the medium surrounding the colonies becomes pink-orange |
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| what is considered a negative reaction in the HE agar lactose fermentation assay? |
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| if the colonies appear blue-green |
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| What is a positive reaction for the H2S production on HE plates? |
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| black center of colony |
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| what is nitrogen fixation? |
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| the reduction of atmospheric nitrogen to ammonia or ammonium. |
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| what is the name of the bacteria genus that fixes nitrogen? |
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| rhizobium |
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| what are some examples of the legume family? |
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| clover, alfalfa, pea, soybeans |
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| what is the symbiotic relationship between nodules and nitrogen fixing bacteria? |
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| the nitrogen fixing bacteria give the plant nitrogen, the plant gives the bacteria shelter |
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| what is nitrogenase? |
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| the enzyme that turns N2 to NH4+ |
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| how do nitrogen fixing bacteria affect the soil? |
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| make it more fertile because they release ammonia after the nearby plants die |
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| what type of cells are rhizobium cells? |
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| gram negative rods...once the symbiotic relationship is established, they change shapes and turn into club-shaped bacteriod forms |
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| what is weird about rhizobium cells after they are in an established relationship with a plant? symbiotically? |
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| they stain gram positive |
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| what is unique about cyanobacteria? |
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| they are able to carry out photosynthesis and use nitrogen to create glucose |
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| can azobacter use photosynthesis? |
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| no |
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| How does mannitol salt broth select nitrogen fixers? |
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| the medium inhibits the growth of non-N2 fixers by denying these species of the nitrogen compounds they need to make amino acids and proteins |
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| Mannitol is used as a selective agent for Azobacter cells. How? |
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| Azobacter cells can survive on mannitol as the only organic molecule available for carbon and energy. But many other nitrogen fixing species would need other nutrients |
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| what shape are azobacter cells? |
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| cysts |
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| what is nitrification? |
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| the process of converting NH4+ to NO2- and then to NO3 |
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| In nitrification, which species first carries out the first oxidation? |
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| nitrosomas |
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| in nitrification, which species carries out the second oxidation? |
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| nitrobacter |
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| are nitrosomas and nitrobacter photosynthetic? |
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| noo, chemotrophic |
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| what is leaching? |
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| the removal of nitrates from the soil by water |
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| what are examples of denitrifyers? |
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| bacillus and pseudomonas |
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| what is a positive result for the test of denitrification? |
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| bubble |
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| in the indole assay's Kovac's reagent, what are the roles of butanol and dimethylaminobenzaldehyde? |
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| butanol- absorbes the indole, dimethyl amino: combines with reagent's aldehyde group to produce red color. |
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| Say you started with a mixed culture of E. coli and Enterobacter aerogenes. If you were going to choose one of the media described in this lab to favor the growth of Enterobacter aerogenous over E. coli, which medium would you choose? |
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| methyl red indicator, clearly turned the E. aero yellow and the E.coli red ..this means that E. coli ferments more lactose than E. aerogenes |
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| Why is the urease assay so helpful for the identification of Proteus species, and why is this relevant to the Proteus species' ability to cause kidney infections? |
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| production of ammonia fro urea damages kidneys |
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| How or why can two different isolates or pure culture produce two different brocades and yet be identified by the Enterotube system as being the same species ? |
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| there are different strains within species "not genetically identical" |
