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Microbiology > Lab Final > Flashcards

Lab Final Flashcards

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Biology 101 flashcards
1
Q

what is the most important nutrient for bacteria to have

A

carbon (autotroph versus heterotroph)

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2
Q

what influence does temperature have on bacterial growth

A

influences the rate of chemical reactions in the cell

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3
Q

what are the two main types of bacterial cultivation

A

defined media and complex media

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4
Q

how are defined media composed

A

composed of known quantities of chemically pure and specific organic/inorganic compounds. (very specific recipe)

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5
Q

what are two examples of defined media

A

inorganic synthetic broths or glucose salt broths

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6
Q

what are complex media

A

exact chemical composition not known. made from animal and plant tissue extracts.

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7
Q

what are two examples of complex media

A

nutrient broths and yeast extract broths

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8
Q

what is a nutrient broth made of

A

peptone and beef extract

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9
Q

what is yeast extract broth made of

A

nutrient broth (peptone and beef extract) plus yeast

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10
Q

what does turbidity indicate

A

bacterial growth

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11
Q

what are selective media

A

used to isolate specific groups of bacteria

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12
Q

how do selective media work

A

chemicals to inhibit growth of one organism but allows growth of another organism

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13
Q

what are three examples of selective media

A

phenylethyl alcohol (pea), crystal violet, sodium chloride

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14
Q

what are differential/selective media

A

will produce a change in appearance of bacterial growth on or around the colonies, and also can inhibit growth of some organisms

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15
Q

what are examples of differential/selective media

A

MSA, MacConkey’s, Eosin-methylene blue

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16
Q

how does MSA work

A

inhibits by salt concentration, mannitol (to ferment) and a pH indicator for detecting fermentation (yellow -)

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17
Q

how does macconkeys work

A

does not allow gram positive to grow, fermentation of lactose with ph indicator

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18
Q

how does eosin-methylene blue work

A

fermentation of lactose, doesnt grow gram positive

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19
Q

how does PEA work

A

(phenylethyl alcohol) only allows gram positive growth

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20
Q

what are enriched media

A

media with highly nutritious materials

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21
Q

what are some nutrients used in enriched media

A

blood, serum, yeast

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22
Q

how do most microorganisms obtain their energy

A

through a series of orderly and integrated enzymatic reactions leading to biooxidation of carbohydrates

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23
Q

why would an organism use one carbohydrate over another

A

varying enzyme compliments

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24
Q

what is the function of carbohydrate tests

A

to determine fermantative pathways

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25
Q

what is the pathway used to describe the fermantation of carbohydrates

A

glycolytic pathway

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26
Q

one mole of glucose is turned into what

A

two moles of pyruvic acid

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27
Q

how is fermentative degredation achieved

A

under anaerobic conditions in a fermentation tube with a durham tube

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28
Q

what is typically found in a fermentation broth

A

nutrient broth with a specific carbohydrate and a pH indicator

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29
Q

why is there only a specific carbohydrate included in a fermentation broth

A

determines if the organism can ferment that specific carbohydrate (indicated by the pH indicator)

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30
Q

typically if fermentation has occurred, what colour will the broth turn

A

will turn yellow which is a negative result

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31
Q

what are positive and negative results based on acidity

A

positive is if it is basic, negative if it is acidic

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32
Q

what is the longest a broth should go

A

48 hours is the longest.

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33
Q

when should you let a broth go to 48 hours

A

if not positive after 18-24 hour window, let it go to a seconf period (up to 48 hours)

34
Q

how do you get a negative result in carbohydrate fermentation

A

when the carbohydrate present is not used, the organism will use the peptones in the nutrient broth, using these causes basic conditions (ammonia)

35
Q

lactose fermentation can distingush between what types of bacteria

A

enteric and non-enteric

36
Q

what does TSI stand for

A

triple sugar iron agar test

37
Q

what is the function of a TSI test

A

differentiate between groups of the enterobacteriaceae. tells fermentation patterns and hydrogen sulfide production

38
Q

what carbohydrate concentration is found in TSI

A

equal concentrations of lactose, sucrose, and glucose (1%)

39
Q

what pH indicator is found in TSI

A

phenol red

40
Q

how do you innoculate a tsi slant

A

stab and streak

41
Q

how is gas production measured in TSI slants

A

there can be gas bubbles in the media, they can even split the media

42
Q

how can you tell if only glucose production has occurred in TSI slants

A

red slant, yellow butt, with or without gas production

43
Q

how can you tell if lactose or sucrose production has occurred in a TSI slant

A

yellow slant, yellow butt, with or without gas

44
Q

how can you tell that no carbohydrate fermentation has occurred in a TSI slant

A

red slant, red butt

45
Q

what is the window of time for a TSI slant

A

18-24 hours strictly

46
Q

how can you tell if hydrogen sulfide production has occurred in a TSI slant

A

the mid section will be black (ferrous sulfate reacting with sodium thiosulfate)

47
Q

what bacteria of medical importance can be found in the enterobacteriaceae

A

pathogens, occassional pathogens, normal intestinal flora

48
Q

what comprises the IMViC test

A

indole, methyl red, voges- proskauer, citrate)

49
Q

what is tryptophan used for

A

ability of a bacterium to hydrolyze tryptophan in the presence of indole

50
Q

what media do you use for indole

A

SIM

51
Q

how do you detect the presence of indole in SIM agar

A

by adding Kovac’s reagent

52
Q

how do you tell if a positive result for indole in SIM media

A

after adding kovacs if positive it will turn cherry red

53
Q

what is the time period for indole (SIM)

A

24-48 hours

54
Q

how much kovacs do you add to a SIM tube to detect indole

A

about 10 drops

55
Q

what is the major substrate used by all enteric organisms

A

glucose

56
Q

when doing the methyl red test, if the solution turns red, what result is this

A

positive result with a lower pH (more acidic)

57
Q

how long do you incubate TSB broth

A

24-48 hours

58
Q

what is TSB broth used to detect

A

its the basis for methyl red and voges proskaur tests

59
Q

what does the voges-proskaur test determine

A

ability of an organism to produce nonacidic or neutral end products

60
Q

what is the reagent used in voges proskaur

A

barritts reagent

61
Q

how long does it take to perform the voges proskaur test

A

15 minutes after adding barritts reagent

62
Q

what colour will the solution be if there is a positive result for voges proskaur

A

dark red

63
Q

how do you perform voges proskaur

A

use innoculated TSB broth, add 10 drops barritts A and shake immediately, then add 10 drops barritts B and shake immediately. leave for 15 minutes, shaking occassionally

64
Q

what does the citrate test determine

A

if an organism is able to ferment citrate in the absence of glucose or lactose

65
Q

what is the pH indicator used in the citrate test

A

bromthymol blue

66
Q

what will a citrate positive test show

A

growth on the surface of the slant and a blue colouration

67
Q

what will a citrate negative test show

A

no growth and the media will remain green

68
Q

what is the incubation time for a citrate test

A

24-48 hours

69
Q

how does a SIM tube show hydrogen sulfide production

A

black

70
Q

how can you tell motility of an organism

A

use a SIM tube and when stabbing, if turbidity is outside of the stab line there is motility

71
Q

what pH indicator is found in urease test

A

phenol red

72
Q

what is urease

A

attacks amide of urea and forms an alkaline end product

73
Q

how does the urease pH indicator work

A

urea is split and forms ammonia, this is alkaline and produces a positive red result

74
Q

what is the incubation time for urease

A

24-48 hours

75
Q

what is decarboxylation

A

some organisms have decarboxylase enzymes capable of removing the carboxyl group of an amino acid.

76
Q

what is the pH indicator of decarboxylase tests

A

bromthymol blue

77
Q

what conditions must be met for LDC and ODC

A

anaerobic conditions (no oxygen)

78
Q

how are anaerobic conditions met in ODC and LDC

A

adding mineral oil to the surface of the innoculated broth

79
Q

organisms that have deaminase groups can remove what

A

amino groups from amino acids

80
Q

is performing a phenylalanine test what happens if the organism has phenylalaine deaminase

A

phenylpyruvic acid will be released and a green colour will result (positive result)

81
Q

what reagent is added to phenylalainine tests

A

10% ferric chloride solution

Microbiology (6 decks)

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