Microbiology Lab UTA – Final Questions With Complete
Solutions
Acidophiles Correct Answers below ph 5.5
Add 15 drops of Barrits Reagent A (alpha-napthol). MIX.
Add 5 drops of Barrits reagent B (KOH) to same tube and mix
well to oxygenate for 30 seconds. Vortex if you want. Incubate
up to 1 hour to see result. Correct Answers How to perform
VP test
Advantages to using semi-solid media Correct Answers To
test oxygen requirements, to test motility.
Agar Correct Answers linear polysaccharide polymer derived
from agarose in red algae.
Alcohol Correct Answers 65-70% is most widely used skin
disinfectant.
Alcohol/acetone mixture that dehydrates the cell, shrinking the
cell wall. Correct Answers What are decolorizers composed of
and what do they do?
alkalophiles Correct Answers above 8.5
Anaerobic metabolism by Correct Answers phosphoketolase
pathway
,Anaerobic respiration, where the terminal electron acceptor is an
inorganic molecule other than oxygen Correct Answers Nitrate
reduction is an example of _____
Antibiotics are Correct Answers natural antimicrobial agents
produced by microorganisms that inhibit or kill other
microorganisms.
Antimicrobials Correct Answers any natural/synthetic
substance that kills MOs
antiseptics are Correct Answers bacteriostatic agents
Antiseptics are Correct Answers safe for tissues
Autoclave Correct Answers sterilizes with steam at 121* C,
pressure at 15 PSI for at least 15 min. Tested weekly to daily.
Autoclaving removes the free oxygen in the media. As the agar
cools, oxygen diffuses and creates an OXYGEN
CONCENTRATION GRADIENT ranging from aerobic to
anaerobic. Correct Answers Why is media sterilized using the
autoclave?
Bacillus Correct Answers What shape are Gram (-) cells?
Bacteria require water to maintain Correct Answers cellular
turgor pressure
Bacteria that produce tryptophanase hydrolyze tryptophan, a
component of the peptone in the media, to produce the product
, indole Correct Answers How is the presence of the enzyme
tryptophanase tested for using the SIM media?
bacteriostatic agents Correct Answers inhibit microbial
multiplication without killing
Barritt's Reagents A/B Correct Answers Reagents used for
Voges-Proskauer test?
beads on a chain Correct Answers Morphology of Streptococci
because they can't make cytocrhomes Correct Answers
Streptococci cannot carry out oxidative phosphorylation to
ferment sugars
blue or black shiny slightly raised 1-2 mm colonies Correct
Answers Enterococcus spp.
Calculations for number of bacteria per ml Correct Answers #
of colonies x reciprocal of dilution of sample
Capsule / Glycocalyx Correct Answers Thick, mucoid
polysaccharide layer surrounding all bacterial cells. Prevents
desiccation, guards against the host immune response, and aids
in adhering to host cells.
Capsules resist stains, so basic crystal violet is applied to stain
the interior of the cell while acidic India Ink stains the
background. The capsule appears white. Correct Answers
Capsule Staining
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