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MCB 4403 > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

microbial growth

A

increase in the number of cells through binary fission, asexual reproduction, cloning, etc.

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2
Q

microbe populations increase….

A

exponentially

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3
Q

growth cycle of bacteria: lag phase

A

cells synthesizing materials and not dividing

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4
Q

growth cycle of bacteria: log phase

A

exponential growth

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5
Q

growth cycle of bacteria: stationary phase

A

cells no longer growing

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6
Q

growth cycle of bacteria: death phase

A

lol they die

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7
Q

photoautotroph

A

uses light and CO2 to make energy (plants)

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8
Q

photoheterotroph

A

uses light and organic compounds to make energy (purple nonsulfur bacteria)

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9
Q

chemoautotroph

A

uses chemical sources and CO2 to make energy (iron-oxidizing bacteria)

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10
Q

chemoheterotroph

A

uses chemical sources and organic compounds to make energy (animals, fungi)

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11
Q

culture medium

A

nutrients prepared for microbial growth

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12
Q

sterile

A

no living microbes

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13
Q

inoculum

A

introduction of mircobes into the medium

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14
Q

culture

A

microbes growing in/on culture medium

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15
Q

chemically defined media

A

exact chemical compositions is known

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16
Q

complex media

A

extracts and digests of yeasts, meat, or plants (nutrient broth or agar)

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17
Q

culture media has all materials necessary for growth including…(4)

A
  • electron sources
  • energy sources (if not phototrophic)
  • carbon sources (if not autotrophic)
  • nitrogen sources (if no N2 fixer)
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18
Q

agar

A

used as a solidifying agent for culture media in Petri plates, slants, and deeps

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19
Q

agar is made of complex _____

A

polysaccharides

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20
Q

only one kind of bacteria can grow on MacConkey agar, which is it?

A

Gram-
(Gram+ inhibited by crystal violet and bile salts)

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21
Q

how do you obtain a pure culture?

A

through dilution streaking

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22
Q

dilution streaking

A
  • streak cells on a plate
  • agar inhibits spread of microbes on the plate
  • all cells in a colony derived from a single cell
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23
Q

a pure culture contains…

A

only one species or strain

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24
Q

a colony is a population of cells arising from…

A

a single cell or spore or from a group of attached cells

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25
Q

a colony is also commonly called..?

A

a colony-forming unit (CFU)

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26
Q

dilution in liquid culture (2)

A
  • reduces the number of cells in each tube
  • spread liquid on a plate to see single colonies
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27
Q

how to calculate bacterial growth-viable count

A

(number of colonies on plate) x (reciprocal of dilution sample = number of bacteria/ml

EXAMPLE: (32 colonies on a plate) x (10,000 because the dilution was 1/10,000) = 320,000/ml in the sample

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28
Q

what is the Petroff-Hauser chamber?

A

it is a hemocytometer

29
Q

hemocytometer

A

a counting-chamber device originally designed and usually used for counting blood cells

30
Q

T/F: a hemocytometer can tell is a cell is alive or dead

A

FALSE: it cannot tell the difference and they must use stain to differentiate

31
Q

spectrophotometer

A

measures optical density

32
Q

T/F: A spectrophotometer can’t tell if a cell is alive or dead

A

TRUE

33
Q

flowcytometer

A

a technology that provides rapid multi-parametric analysis of single cells in solution

34
Q

MPN or _____ _____ _____

A

most probable number

35
Q

multiple tube MPN test

A
  • count positive tubes
  • compare with a statistical table
  • used for very low counts
36
Q

biofilms

A

cells acting together that secrete material to hold to a surface

37
Q

quorum sensing

A

cells signal to each other

38
Q

why are biofilms bad for antibiotics?

A

they prevent them from infiltrating

39
Q

Given a log phase bacterial culture with 1x10^6 cells per ml and a generation time of 30 minutes, how long does it take the culture to reach a density of 6.4 x 10^7 cells/ml?

A

1 hour

Work: (1x10^6)x = (6.4x10^7)
x = (6.4x10^7)/(1x10^6)
x = 64 = about 1 hour
(I think)

40
Q

Which of the following uses sunlight for energy and CO2 as a carbon source?

  • photoautotroph
  • chemoautotroph
  • photoheterotroph
  • chemoheterotroph
A

photoautotroph

41
Q

What is the fastest way to measure cell density?

A

spectrophotometer

42
Q

What shorted lag period would most likely be observed if a culture is transfered?

A

from a complex medium to a fresh complex medium

43
Q

Any organism found in ‘extreme’ environments are called…?

A

extremophiles
(extreme to humans)

44
Q

environmental limits on microbial growth (5)

A
  • temperature
  • pH
  • osmolarity
  • oxygen
  • pressure
45
Q

microbes are commonly classified by their environmental niche: hyperthermophile

A

grow above 80ºC

46
Q

microbes are commonly classified by their environmental niche: thermophile

A

grow between 50ºC and 80ºC

47
Q

microbes are commonly classified by their environmental niche: mesophile

A

grow between 15ºC and 45ºC

48
Q

microbes are commonly classified by their environmental niche: psychrophile

A

growth below 15ºC

49
Q

microbes are commonly classified by their environmental niche: alkaliphile

A

growth above pH 9

50
Q

microbes are commonly classified by their environmental niche: neutralophile

A

growth between pH 5 and 8

51
Q

microbes are commonly classified by their environmental niche: acidophile

A

growth below pH 3

52
Q

microbes are commonly classified by their environmental niche: halophile

A

growth in high salt contents

53
Q

microbes are commonly classified by their environmental niche: aerobe

A

growth only in O2

54
Q

microbes are commonly classified by their environmental niche: facultative

A

growth with or without O2

55
Q

microbes are commonly classified by their environmental niche: microaerophile

A

growth only in small amounts of O2

56
Q

microbes are commonly classified by their environmental niche: anaerobe

A

growth only without O2

57
Q

microbes are commonly classified by their environmental niche: barophile

A

growth at high pressures greater than 380 atm

58
Q

microbes are commonly classified by their environmental niche: barotolerant

A

growth between 10 and 495 atm

59
Q

some ‘extremophiles’ are only know from…?

A

DNA sequences obtained from environmental samples

60
Q

growth rate _____ with temperature

A

increases

61
Q

what happens to proteins if temperatures are too high?

A

proteins denature

62
Q

heat shock response

A

emergency proteins are produces to help keep proteins from denaturing

63
Q

what kind of conditions trigger the heat shock response? (3)

A
  • heat
  • high salt concentrations
  • arid conditions
64
Q

temperature and food preservation

A
65
Q

how are thermophiles adapted to high temperatures? (4)

A
  • different amino acids and composition of proteins
  • proteins that stabilize DNA and prevent denaturation
  • more robust chaperone proteins to help fold proteins properly
  • more saturated in linear lipids in the membranes
66
Q

microbes are commonly classified by their environmental niche: barosensitive

A

die at high pressure

67
Q

why are barophiles difficult to study? (3)

A
  • need a submarine or pressure chamber
  • they live at hydrothermal vents
  • deap-sea sites
68
Q

cellular mechanisms in response to osmotic pressure: low

A

mechanosensitive channels relieve stress to release cell content

69
Q
A

MCB 4403 (7 decks)

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