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microbiology > microbial growth and reproduction 9/26 > Flashcards

microbial growth and reproduction 9/26 Flashcards

(67 cards)

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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
what must culture media contain
all the nutrients required by the organism for growth
26
what needs to be taken into account for culture media classification
–chemical constituents from which they are made –physical nature –function
27
what types of culture media are there in general
defined or synthetic and complex
28
what are defined or synthetic media
all components and their concentrations are known
29
what is complex media
•Contain some ingredients of unknown composition and/or concentration
30
what is minimal medium
•media containing minimal nutritional requirements for a particular microorganism; varies from microbe to microbe
31
what is rich medium
medium containing much more than minimal; may have proteins, amino acids, starches, monosaccharides, ion, lipids
32
does minimal or rich medium take longer to grow
minimal
33
what are the types of functional types of media
supportive, enriched, selective, differential
34
what is supportive or general purpose media
–support the growth of many microorganisms (rich media) •e.g., (TSA) tryptic soy agar (rich medium)
35
what is enriched media
–general purpose media supplemented by blood or other special nutrients –e.g., blood agar (TSA + sheep blood) – high in iron
36
what is selective media
* 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
differential media
•Media which allows different microorganisms to grow differently –i.e., blood agar
38
what is pure culture
•population of cells arising from a single cell developed by Robert Koch
39
what does isolation of pure cultures allow for
study of single type of microorganism in mixed culture
40
what techniques are used to isolate pure cultures
Spread plate, streak plate, and pour plate
41
what is the streak plate technique
•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
what is the end product in terms of cells for the streak plate technique
•Each cell can reproduce to form a separate colony (visible growth or cluster of microorganisms) and the colony grows from the original cell
43
what is the spread plate technique
–small volume of diluted mixture containing approximately 30–300 cells is transferred –spread evenly over surface with a sterile bent rod
44
what is the pour plate technique
–sample is serially diluted –diluted samples are mixed with liquid agar –mixture of cells and agar are poured into sterile culture dishes
45
what can the spread and pour plate be used to determine
the number of viable microorganisms in an original sample
46
what could an increase in cellular constituents result in
–increase in cell number –increase in cell size
47
what does growth refer to
population growth rather than growth of individual cells
48
when is the growth curve observed
•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
what is the growth curve plotted as
•logarithm of cell number versus time
50
how many distinct phases does the growth curve have and what are they
3 or 4 distinct phases - –Lag (+/-), exponential, stationary, senescence, and death
51
what does the growth curve look like
52
what is the lag phase of the growth curve and what are examples of this
•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
what is the exponential or log phase of the growth curve
–Cells growing exponentially; cell divisions \> cell deaths because plenty of space and nutrients, and little waste; maximum growth rate
54
what is the stationary phase of the growth curve
–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
what is the death phase of the growth curve
cell deaths \> cell divisions; too much waste and too little nutrients in medium
56
what does entry into the stationary phase activate
survival strategy
57
what are characteristics of survival strategy
–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
what occurs when there is a production of starvation proteins in a starvation response
59
–increase cross-linking in cell wall –Dps protein protects DNA –chaperone proteins prevent protein damage
60
what are persistar cells
–long-term survival –increased virulence -involved in starvation response
61
what are two other hypotheses for the death phase
–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
what is the generation or doubling time
–time required for the population to double in size
63
what does the generation time depend on
–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
what is the best replication time for e.coli
every 20 min
65
what is exponential population growth
population doubling every generation
66
what is the formula for exponential growth
N=No2n N=final cell number No=initial cell number n=number of generations during the period of exponential growth
67
what is the generation time formula
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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