Microbiology Midterm Flashcards
phase microscopy is best used for
live cells
bacteria in milk can survive pasteurization temperatures and cause spoilage or souring of milk, these bacteria are called
thermodurics
what allows bacteria to normally survive hypotonic solutions
cell wall
what is the average ratio of bacteria to human cells in the human body
10 to 1
osmophiles are organisms that can grow
at high concentration of sugar
what is the bacterial arrangement term for cocci arranged in clusters
staphylococcal
while trying to view a specimen under the light microscope, turning the coarse or fine focus knows adjusts the distance between which of the following parts
the stage and the objective lenses
these kinds of bacteria use aerobic respiration to make their energy but can only tolerate very low concentrations of oxygen
microaerophiles
some bacteria can grow at 4C and can cause food spoilage they are called
psychrotrophs
Gram’s iodine is added to the Gram stain procedure for what reason
it combines with the crystal violet and forms an insoluble complex in Gram positive cells
in a typical light microscope, what are the series of lenses that focus light onto the specimen called
condenser
when we say bacteria are ubiquitous, we mean
they are found everywhere
IMViC tests are used to
differentiate between E. coli and E. aerogenes
what type of slides would you most likely look at with phase-contrast microscopy
wet mount slides
what type of media would you use for the growth of fastidious organisms
enriched media
which type of organism does NOT need oxygen and is NOT poisoned by it
aerotolerant
what are the two types of light rays important for phase contrast microscopy
direct rays and diffracted rays
which of the following microorganisms would you NOT be able to observe using light microscopy
ultramicrobacteria (184 nm long, shorter than other options)
coliforms have which of the following characteristics
- gram negative
- facultative anaerobes
- non-endospore forming rods
- ferment lactose to produce gas
most human pathogens belong to what group of bacteria
mesophiles
who developed the phase contrast microscope
Frits Zernike
if you transfer 1 mL of culture into 99mL of sterile water and then add 0.1 mL of that to an agar plate, what is the final dilution of the culture on that plate
1: 1000
respiration uses what as the terminal electron acceptor
oxygen
endospores are highly resistant to heat, radiation, acids and many chemicals because of their protective protein coating known as
exosporium
after the alcohol step in the gram stain procedure, what color will gram negative bacteria be
clear
why might a bacterial culture give Gram-variable results
- the culture is too old
- the culture is a Bacillus species
- the smear is too thick
- it was over decolorized
acid-fast staining is used
when the bacteria have a high mycolic acid content
Brownian motion is caused by
Bombarding molecules
as you increase the magnification, __________ decreases
- the field of view
- the working distance
which of these tests is not matched correctly with a material used in the test
confirmed test …. tryptone glucose extract agar
correct:
- presumptive test … lactose broth
- presumptive test … durham dube
- confirmed test … endo broth
- confirmed test … EMB agar
which of these can NOT be measured by a spectrophotometer
Most probable number
which of the following environments is most likely to cause plasmolysis
hypertonic
what’s the most critical step of the gram stain
using the alcohol
which setting should the condenser be on when looking at bacteria under oil immersion using phase contrast microscopy
3 (x100?)
which of the following is NOT a part of a bacterial flagellum
N-ring
yes:
- filament
- L-ring
- S-ring
- hook
motility medium can be used to determine if bacteria are motile because
it has an agar concentration of ~ 0.4%
where would you NOT normally find bacteria among the following
your blood
your light microscope has a limit resolution of (??)
0.2 micrometers
which of these statements is true
-the presence of microorganisms in food doesn’t mean it has potential to cause disease
it is easier to test water for presence of indicator bacteria such as
E. coli
microorganisms used enzymes like catalase and peroxidase to
convert toxic oxygen forms to less harmful compounds
Thermodurics are bacteria capable of what?
survival at high temperature
which of these is a reason microbiologists use acid-fast staining
able to stain cells with a high lipid content cell wall
which of the following is an example of a bacterium that is present in the form of a tetrad cocci
micrococcus leteus
the telescopic eyepiece is used for
aligning the phase rings
what is the bacterium that has two bundles of flagella at opposite poles called
amphitrichous
which of these techniques is used in the isolation of pure bacterial cultures
streak plate
what is the cell wall of bacteria composed of
peptidoglycan
what microscope part should never be used with the two highest power objectives
coarse focus know
