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microbio lab > lab quizzes > Flashcards

lab quizzes Flashcards

1
Q

Calculate the total magnification it a specimen is viewed under the high-dry objective (40x) objective

A

40 x 10 = 400x

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2
Q

Define “working distance”

A

The distance between the specimen and objective lens

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3
Q

How do you regulate the amount of light entering the condenser?

A

Iris diaphragm

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4
Q

What controls on the microscope affect the amount of light reaching the ocular lens?

A

Iris diaphragm and rheostat (intensity)

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5
Q

What are the 3 basic shapes of bacteria?

A

Bacillus, coccus, and spiral

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6
Q

Why is it desirable for objectives to be parfocal?

A

If one lens is focused, all of the lenses will be in partial focus

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7
Q

What is the function of the condenser and where is it located?

A

Has lenses to direct light to the specimen and is located below the stage

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8
Q

What needs to be done if microbial cultures are spilled?

A

Soak paper tower w/ disinfectant and let sit for 20 mins before wiping

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9
Q

How does true motility differ from brownian movement?

A

True motility: object moves from one point to another
Brownian movement: object shakes/ bounces bc of liquid molecules striking against it

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10
Q

For illumination, you shone increase/decrease light w/ increasing power

A

Increase

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11
Q

What are the steps of wet mount procedure

A

Add specimen suspended in liquid on slide, add coverslip, view w/ microscope

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12
Q

Why do we need petroleum jelly for the hanging drop procedure w/ a depression slide

A

To seal the coverslip and prevent evaporation

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13
Q

What is the purpose of adding methylcellulose to a slide

A

To slow down the microbes

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14
Q

Mode of motility for amoeba proteus, euglena, and paramecium

A

Pseudopods, flagella, and cilia

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15
Q

How do Cyanobacteria differ from algae

A

Cyanobacteria are prokaryotic cells w/o organelles

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16
Q

Which of the following is likely to phagocytose a food particle: volvox (pond algae), HIV virus, E. coli, amoeba proteus, penicillium chrysogenum, S. Aureus

A

Amoeba proteus

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17
Q

What do dinoflagellates in the genus Alexandria produce

A

Toxins

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18
Q

What do dinoflagellates in the genus Alexandria produce

A

Toxins

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19
Q

Define heterocyst

A

Specialized cell that fixes nitrogen

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20
Q

Define cytosome

A

Mouth-like opening

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21
Q

When inoculating, if you missed the opening and touched the outside of the tube instead, how should you proceed and why?

A

Flame the inoculating tool and tube because the tube may not have been fully sterilized

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22
Q

What is the hyphal strand that is separated by a cell wall

A

septate hyphae

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23
Q

Is yeast uni or multicellular

A

Unicellular

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24
Q

Sabouraud dextrose agar (SDA) is used to culture fungi. This is a selective media that contains simple nutrients and has a low pH why?

A

To inhibit growth of other organisms

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25
Q

What is the connect inoculating instrument: (1) agar slant, (2) agar deep, (3) lb broth, (4) lb agar Petri dish

A

(1) loop, (2) needle, (3) loop, (4) loop

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26
Q

What method of sterilization is suitable for culture media containing fetal bone serum (FBs)? (FBs is heat-sensitive)

A

Cold sterilization w HEPA filters

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27
Q

What are the phylum of these fungi: (1) Rhizopus stolonifera, (2) penicillium chrysogenum, (3) coprinus mushroom

A

(1) zygomycota, (2) ascomycota, (3) basidiomycota

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28
Q

How does differential staining differ from simple staining

A

using 2 reagents instead of 1

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29
Q

what are 2 methods to fix bacterial smears

A
  1. heat fixing
  2. chemical fixing using 95% methanol
30
Q

why is a thin layer of bacteria desired for a smear

A

otherwise, it will be too layered and crowded for viewing

31
Q

which inoculating instrument is used for a bacterial smear from liquid media

A

loop

32
Q

what is the value of using a negative stain technique to determine the cell morphology of bacterial cell

A

the cell remains colorless while the surrounding media is stained, we can view the cell’s morphology without heat fixing

33
Q

what dye is used in the direct staining procedure

A

methylene blue

34
Q

what is the major difference in the outcome of the direct and indirect staining procedures

A

direct: dye stains the cells
indirect: dye stains the surrounding media and cells are colorless

35
Q

define bacterial smear

A

thin film of bacteria on a slide

36
Q

when micrococcus luteus and e.coli are used for indirect staining:
1. what dye is used?
2. chromophore of the dye
3. shape of bacterial cells
4. color of bacterial cells

A
  1. nigrosin
  2. negative
  3. coccus/spheres and bacillus/rods
  4. colorless
37
Q

what is the colorless halo around some bacteria that were stained with both acidic and basic dyes

A

capusle

38
Q

what color is mycobacterium tuberculosis in acid-fast staining

A

red

39
Q

b.subtilis produces endospores if the conditions are no longer favorable for vegetative growth. what colors are expected for:
1. endospores
2. vegetative cells

A
  1. green
  2. red
40
Q

how do you remove liquid from ELISA microplate

A

tap on paper towel

41
Q

an old culture of 72 hours is used for endospore staining. the culture is gram-positive but the gram-stain shows pink-red rods. what is your conclusion?

A

since the culture is old, past 24 hours the cell walls begin to degrade. this prevents the CV-I complex from forming

42
Q

when conducting a gram-stain, you run out of safranin. can you still interpret your results?

A

yes because gram-pos will be purple and gram-neg will be colorless

43
Q

what is the difference between selective and differential media

A

selective: inhibits growth of other organisms and only allows one type of microbe to grow
differential: allows all microbes to grow to show differences based on by-products

44
Q

what does ELISA stand for

A

enzyme-linked immunosorbent assay

45
Q

what is the chromogenic substrate necessary for result interpretation of ELISA

A

TMB

46
Q

two similarities between direct and indirect ELISA

A
  1. positive result is blue
  2. involves enzyme-linked antibodies
47
Q

two differences between direct and indirect ELISA

A
  1. indirect is cheaper
  2. direct detects antigens and indirect detects antibody
48
Q

what is tween-20 and what function does it play in ELISA

A

a chemical in the buffer which acts like a blocking agent

49
Q

if the washing step after the addition of the secondary antibody was omitted when performing indirect ELISA, what is the expected outcome for +/- controls and test wells? why?

A

pos control: blue
neg control: blue
test wells: blue
there would be free-floating secondary antibodies in the well which bind to the substrate

50
Q

zombie virus is spreading on earth, there is a treatment but it must be distributed to infected people within 3 days of exposure. design a diagnostic assay that will confirm the presence of the virus.

A

direct elisa

51
Q

what is a media that is both selective and differential

A

MSA (mannitol salt agar)

52
Q

what is the desired outcome of the dilution streak method

A

to see individual colonies

53
Q

what causes metallic green appearance on EMB plate

A

precipitation of methylene blue from fermentation and production of acid

54
Q

two advantages of the dilution streak plate method

A
  1. can see individual colonies
  2. observing colony morphology
55
Q

two disadvantages of dilution streak plate method

A
  1. can’t count colonies
  2. time consuming because of incubation
56
Q

what is the dilution if you mix 10mL bacterial culture int 10ml sterile LB broth

A

volume of sample/total volume = 10/20 = 1:2 dilution

57
Q

what does EMB agar inhibit

A

gram-positive

58
Q

what does PEA agar inhibit

A

gram-negative

59
Q

what makes the MSA plate selective and differential

A

selective: 7.5% NaCl
differential: 1% mannitol

60
Q

how do you test to find out if a microbe is producing catalase? what do you add?

A

catalase test; add 3% H2O2

61
Q

in the presence of oxygen, what color does resazurin have?

A

pink

62
Q

why are palladium pellets added to the brewer jar with a gas pack

A

to catalyze reaction between hydrogen and oxygen to form water

63
Q

what is a microaerophile

A

uses limited oxygen and higher amounts can be inhibitory

64
Q

how do you fix a mixed tube of thioglycolate without using a fresh one

A

heat up the tube and wait for the layers to separate

65
Q

is an environment of .85% NaCl hyper or hypotonic for a microbe

A

hypertonic

66
Q

why is agar used as a solidifying agent instead of gelatin?

A

gelatin will get metabolized and agar will not

67
Q

what is the color of phenol red in neural ph and in presence of acid

A

neutral: red
acidic: yellow

68
Q

what is acetoin

A

neutral end-product of fermentation

69
Q

what is amylase

A

exoenzyme that hydrolyzes starch into smaller carbohydrates

70
Q

what is the visual outcome of MRVP test if acetoin is present

A

MR test: yellow
VP: red ring

71
Q

what is the ability of the lenses to reveal fine detail or distinguish between two points called

A

resolving power

72
Q

how is the inoculated agar plate incubated and why

A

upside down to prevent water from condensation to mix with the culture

microbio lab (2 decks)

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