Microbiology Midterm

Question 1

phase microscopy is best used for

Answer 1

live cells

Question 2

bacteria in milk can survive pasteurization temperatures and cause spoilage or souring of milk, these bacteria are called

Answer 2

thermodurics

Question 3

what allows bacteria to normally survive hypotonic solutions

Answer 3

cell wall

Question 4

what is the average ratio of bacteria to human cells in the human body

Answer 4

10 to 1

Question 5

osmophiles are organisms that can grow

Answer 5

at high concentration of sugar

Question 6

what is the bacterial arrangement term for cocci arranged in clusters

Answer 6

staphylococcal

Question 7

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

Answer 7

the stage and the objective lenses

Question 8

these kinds of bacteria use aerobic respiration to make their energy but can only tolerate very low concentrations of oxygen

Answer 8

microaerophiles

Question 9

some bacteria can grow at 4C and can cause food spoilage they are called

Answer 9

psychrotrophs

Question 10

Gram’s iodine is added to the Gram stain procedure for what reason

Answer 10

it combines with the crystal violet and forms an insoluble complex in Gram positive cells

Question 11

in a typical light microscope, what are the series of lenses that focus light onto the specimen called

Answer 11

condenser

Question 12

when we say bacteria are ubiquitous, we mean

Answer 12

they are found everywhere

Question 13

IMViC tests are used to

Answer 13

differentiate between E. coli and E. aerogenes

Question 14

what type of slides would you most likely look at with phase-contrast microscopy

Answer 14

wet mount slides

Question 15

what type of media would you use for the growth of fastidious organisms

Answer 15

enriched media

Question 16

which type of organism does NOT need oxygen and is NOT poisoned by it

Answer 16

aerotolerant

Question 17

what are the two types of light rays important for phase contrast microscopy

Answer 17

direct rays and diffracted rays

Question 18

which of the following microorganisms would you NOT be able to observe using light microscopy

Answer 18

ultramicrobacteria (184 nm long, shorter than other options)

Question 19

coliforms have which of the following characteristics

Answer 19

• gram negative
• facultative anaerobes
• non-endospore forming rods
• ferment lactose to produce gas

Question 20

most human pathogens belong to what group of bacteria

Answer 20

mesophiles

Question 21

who developed the phase contrast microscope

Answer 21

Frits Zernike

Question 22

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

Answer 22

1: 1000

Question 23

respiration uses what as the terminal electron acceptor

Answer 23

oxygen

Question 24

endospores are highly resistant to heat, radiation, acids and many chemicals because of their protective protein coating known as

Answer 24

exosporium

Question 25

after the alcohol step in the gram stain procedure, what color will gram negative bacteria be

Answer 25

clear

Question 26

why might a bacterial culture give Gram-variable results

Answer 26

• the culture is too old
• the culture is a Bacillus species
• the smear is too thick
• it was over decolorized

Question 27

acid-fast staining is used

Answer 27

when the bacteria have a high mycolic acid content

Question 28

Brownian motion is caused by

Answer 28

Bombarding molecules

Question 29

as you increase the magnification, __________ decreases

Answer 29

• the field of view

- the working distance

Question 30

which of these tests is not matched correctly with a material used in the test

Answer 30

confirmed test …. tryptone glucose extract agar

correct:

• presumptive test … lactose broth
• presumptive test … durham dube
• confirmed test … endo broth
• confirmed test … EMB agar

Question 31

which of these can NOT be measured by a spectrophotometer

Answer 31

Most probable number

Question 32

which of the following environments is most likely to cause plasmolysis

Answer 32

hypertonic

Question 33

what’s the most critical step of the gram stain

Answer 33

using the alcohol

Question 34

which setting should the condenser be on when looking at bacteria under oil immersion using phase contrast microscopy

Answer 34

3 (x100?)

Question 35

which of the following is NOT a part of a bacterial flagellum

Answer 35

N-ring

yes:

• filament
• L-ring
• S-ring
• hook

Question 36

motility medium can be used to determine if bacteria are motile because

Answer 36

it has an agar concentration of ~ 0.4%

Question 37

where would you NOT normally find bacteria among the following

Answer 37

your blood

Question 38

your light microscope has a limit resolution of (??)

Answer 38

0.2 micrometers

Question 39

which of these statements is true

Answer 39

-the presence of microorganisms in food doesn’t mean it has potential to cause disease

Question 40

it is easier to test water for presence of indicator bacteria such as

Answer 40

E. coli

Question 41

microorganisms used enzymes like catalase and peroxidase to

Answer 41

convert toxic oxygen forms to less harmful compounds

Question 42

Thermodurics are bacteria capable of what?

Answer 42

survival at high temperature

Question 43

which of these is a reason microbiologists use acid-fast staining

Answer 43

able to stain cells with a high lipid content cell wall

Question 44

which of the following is an example of a bacterium that is present in the form of a tetrad cocci

Answer 44

micrococcus leteus

Question 45

the telescopic eyepiece is used for

Answer 45

aligning the phase rings

Question 46

what is the bacterium that has two bundles of flagella at opposite poles called

Answer 46

amphitrichous

Question 47

which of these techniques is used in the isolation of pure bacterial cultures

Answer 47

streak plate

Question 48

what is the cell wall of bacteria composed of

Answer 48

peptidoglycan

Question 49

what microscope part should never be used with the two highest power objectives

Answer 49

coarse focus know