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microbiology > microbial growth and reproduction 9/26 > Flashcards

microbial growth and reproduction 9/26 Flashcards

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Biology 101 flashcards
1
Q

what must microorganisms replicate

A

genetic material (DNA), cytoplasm, and cytoplasmic structures

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2
Q

what are reproductive strategies of eukaryotic microbes

A

–asexual (mitosis) and sexual (meiosis- start with diploid)

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3
Q

what do mitosis and meosis refer to

A

the nucleus

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4
Q

are bacteria and archaea reproductive strategies haploid or diploid

A

haploid

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5
Q

what kind of reproductive strategies do bacteria and archaea have

A

•asexual - binary fission, budding (most common), filamentous

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6
Q

what must bacteria and archae do prior to cell division

A

replicate and segregate the genome

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7
Q

what is cell divison

A

•each daughter cell receives genetic material and sufficient copies of all other cell constituents to exist as an independent cell

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8
Q

what are two common ways of cell division for prokaryotes and eukaryotes

A

binary fission and budding

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9
Q

what is binary fission

A

cell gets roughly twice its size and then divides the genetic material and cytoplasm equally between the two cells

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10
Q

what is budding

A

a piece of the cell, containing the genetic material but only a little cytoplasm, pinches off to form a new cell. It will then grow bigger

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11
Q

what is the cell cycle

A

•sequence of events from formation of new cell through the next cell division

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12
Q

what do most bacteria/prokaryotes divide by

A

binary fission

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13
Q

what two pathways function during the cell cycle

A

–1) DNA replication and partition

–2) Cytokinesis – division of cytoplasm and structures within

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14
Q

what shape are most bacterial chromosomes

A

circular

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15
Q

origin of replication in bacteria

A
  • single
  • site at which replication begins
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16
Q

what is the terminus

A

site where replication is terminated and is located opposite the origin

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17
Q

what is a replisome

A

group of proteins needed for DNA synthesis

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18
Q

what direction does DNA replication proceed in

A

both directions from the origin

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19
Q

what is chromosome partitioning

A

2 daughter chromosomes moved to opposite ends

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20
Q

what is MreB (murein cluster B)

A

an actin homolog that plays a role in chromosome segregation; new origins assocate with MreB tracks and if MreB is mutated chromosomes do not segregate

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21
Q

an actin homolog in proks is analagous to what in eukaryotes

A

microtubules

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22
Q

what is cytokinesis

A

-septation: formation of cross walls between daughter cells directed by several enzymes in multiple steps

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23
Q

what do you need to do with microorganisms in the lab

A

grow, transport, and store

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24
Q

what kind of preparation can culture media be in general

A

solid or liquid

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25
Q

what must culture media contain

A

all the nutrients required by the organism for growth

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26
Q

what needs to be taken into account for culture media classification

A

–chemical constituents from which they are made

–physical nature

–function

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27
Q

what types of culture media are there in general

A

defined or synthetic and complex

28
Q

what are defined or synthetic media

A

all components and their concentrations are known

29
Q

what is complex media

A

•Contain some ingredients of unknown composition and/or concentration

30
Q

what is minimal medium

A

•media containing minimal nutritional requirements for a particular microorganism; varies from microbe to microbe

31
Q

what is rich medium

A

medium containing much more than minimal; may have proteins, amino acids, starches, monosaccharides, ion, lipids

32
Q

does minimal or rich medium take longer to grow

A

minimal

33
Q

what are the types of functional types of media

A

supportive, enriched, selective, differential

34
Q

what is supportive or general purpose media

A

–support the growth of many microorganisms (rich media)

•e.g., (TSA) tryptic soy agar (rich medium)

35
Q

what is enriched media

A

–general purpose media supplemented by blood or other special nutrients

–e.g., blood agar (TSA + sheep blood) – high in iron

36
Q

what is selective media

A
  • Favor the growth of some microorganisms and inhibit growth of others (has inhibiting agent)
  • e.g., MacConkey agar

–selects for gram-negative bacteria

•Crystal violet is inhibiting agent for gram + bacteria

37
Q

differential media

A

•Media which allows different microorganisms to grow differently

–i.e., blood agar

38
Q

what is pure culture

A

•population of cells arising from a single cell developed by Robert Koch

39
Q

what does isolation of pure cultures allow for

A

study of single type of microorganism in mixed culture

40
Q

what techniques are used to isolate pure cultures

A

Spread plate, streak plate, and pour plate

41
Q

what is the streak plate technique

A

•Involves technique of spreading a mixture of cells on an agar surface so that individual cells are well separated from each other

–involves use of bacteriological loop

42
Q

what is the end product in terms of cells for the streak plate technique

A

•Each cell can reproduce to form a separate colony (visible growth or cluster of microorganisms) and the colony grows from the original cell

43
Q

what is the spread plate technique

A

–small volume of diluted mixture containing approximately 30–300 cells is transferred

–spread evenly over surface with a sterile bent rod

44
Q

what is the pour plate technique

A

–sample is serially diluted

–diluted samples are mixed with liquid agar

–mixture of cells and agar are poured into sterile culture dishes

45
Q

what can the spread and pour plate be used to determine

A

the number of viable microorganisms in an original sample

46
Q

what could an increase in cellular constituents result in

A

–increase in cell number

–increase in cell size

47
Q

what does growth refer to

A

population growth rather than growth of individual cells

48
Q

when is the growth curve observed

A

•when microorganisms are cultivated in batch culture

–culture incubated in a closed vessel with a single batch of medium (a.k.a. closed culture)

49
Q

what is the growth curve plotted as

A

•logarithm of cell number versus time

50
Q

how many distinct phases does the growth curve have and what are they

A

3 or 4 distinct phases - –Lag (+/-), exponential, stationary, senescence, and death

51
Q

what does the growth curve look like

A
52
Q

what is the lag phase of the growth curve and what are examples of this

A

•Lag phase – does not always occur

–Interval of time between when a culture is inoculated and when growth begins

  • cell synthesizing new components
  • e.g., to replenish spent materials
  • e.g., to adapt to new medium or other conditions such as a change in temperature
53
Q

what is the exponential or log phase of the growth curve

A

–Cells growing exponentially; cell divisions > cell deaths because plenty of space and nutrients, and little waste; maximum growth rate

54
Q

what is the stationary phase of the growth curve

A

–Growth rate of population is zero

–Either an essential nutrient is used up or waste product of the organism accumulates in the medium; also less space

-cell divisions = cell deaths (equal amount)

55
Q

what is the death phase of the growth curve

A

cell deaths > cell divisions; too much waste and too little nutrients in medium

56
Q

what does entry into the stationary phase activate

A

survival strategy

57
Q

what are characteristics of survival strategy

A

–morphological changes

•e.g., endospore formation

–Decrease in size, protoplast shrinkage, and nucleoid condensation

–RpoS protein assists RNA polymerase in transcribing genes for starvation proteins

58
Q

what occurs when there is a production of starvation proteins in a starvation response

A
59
Q

–increase cross-linking in cell wall

–Dps protein protects DNA

–chaperone proteins prevent protein damage

A
60
Q

what are persistar cells

A

–long-term survival

–increased virulence

-involved in starvation response

61
Q

what are two other hypotheses for the death phase

A

–cells are Viable But Not Culturable (VBNC)

  • cells alive, but dormant, capable of new growth when conditions are right
  • Programmed cell death

–fraction of the population genetically programmed to die (commit suicide)

62
Q

what is the generation or doubling time

A

–time required for the population to double in size

63
Q

what does the generation time depend on

A

–Varies depending on species of microorganism and environmental conditions

–Range is from 10 minutes for some bacteria to several days for some eukaryotic microorganisms

64
Q

what is the best replication time for e.coli

A

every 20 min

65
Q

what is exponential population growth

A

population doubling every generation

66
Q

what is the formula for exponential growth

A

N=No2n

N=final cell number

No=initial cell number

n=number of generations during the period of exponential growth

67
Q

what is the generation time formula

A

g=t/n

t=duration of exponential growth

n=number of generations during the period of exponential growth

microbiology (11 decks)

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