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Microbiology Chapter 3 Microbial Metabolism > Chapter 5: Microbial Growth and its Control > Flashcards

Chapter 5: Microbial Growth and its Control Flashcards

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Biology 101 flashcards
1
Q

Growth

A

-increases in the number of cells

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2
Q

Binary fission

A

-cell division following enlargement of cell to twice its minimum size

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3
Q

One generation

A
  • cell elongation
  • septum formation
  • completion of septum; formation of walls; cells separate
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4
Q

Septum

A

-partition between dividing cells, pinches off between two daughter cells

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5
Q

Generation time

A
  • time required for microbial cells to double in number

- depends on nutritional and generic factors and temperature

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6
Q

During cell division

A

-each daughter cell receives a chromosome and sufficient copies of all other constituents to exist as an independent cell

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7
Q

Budding

A
  • results from unequal cell growth and forms totally new daughter cell
  • form cytoplasmic extensions such as stacks (caulobacter), hyphae, (hyphomicrobium), and appendages (ancalomicrobium)
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8
Q

Cytoplasmic structure

A

-are not partitioned and remain in old cell

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9
Q

Cell division in bacteria

A
  • equal products of cell division
    • binary fission: most bacteria
  • unequal products of cell division
    • simple budding: pirellula, blastobacter
    • budding from hyphae: hyphomicrobium, rhodomicrobium, pedomicrobium
    • cell division of staked organism: caulobacter
    • polar growth without differentiation of cell size: rhodopseudomonas, nitrobacteria, methylosinus
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10
Q

Planktonic growth

A

-growth as suspension

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11
Q

Sessile growth

A
  • attached to surface
  • can develop into biofilms
  • attached polysaccharide matrix containing embedded bacteria
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12
Q

Biofilms form in stages

A
  • planktonic cells attach

- sticky matrix forms

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13
Q

Microbial mats

A

-multilayered sheets with different in each layer

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14
Q

BiofIlms

A
  • prevent harmful chemicals from penetrating
  • prevent protists from grazing
  • prevent washing away of cells
  • affect human health
  • water distribution systems
  • fuel storage
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15
Q

Exponential growth

A

-growth of a microbial population in which cell numbers double within a specific time interval

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16
Q

N=N_02^n (2^0→2^1→2^2)

A
  • a relationship exists between the initial number of cells present in a culture and the number present after a period of exponential growth
  • N is the final cell number
  • N_0 is the initial cell number
  • n is the number of generations during the period of exponential growth
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17
Q

g=t/n

A
  • generation time (g) of the exponentially growing population
  • t is the duration of exponential growth (days/hours/minutes)
  • n is the number of generations during the period of exponential growth
  • can be calculated from slope of the straight-line logarithmic growth plot
18
Q

Instantaneous growth rate constant

A

-(k) expresses rate of growth at any instant (measure in h^-1)

19
Q

Instantaneous growth rate

A
  • (k) is calculated as k=0.693/g

- useful for optimizing culture conditions for microorganism growth

20
Q

Batch culture

A

-a closed-system microbial culture of fixed volume

21
Q

Typical growth curve for population of cells grown in a closed system is characterized by four phases

A
  • lag phase
  • exponential phase
  • stationary phase
  • death phase
22
Q

Lag phase

A
  • interval between inoculation of a culture and beginning growth
  • time needed for biosynthesis of new enzymes and to produce required metabolites before growth can begin
23
Q

Exponential phase

A

-cells in this phase are typically in the healthiest state

24
Q

Stationary phase

A
  • growth rate of population is zero
  • either an essential nutrient is used up or waste products accumulate
  • some cells grow while others die, balancing each other
25
Q

Death phase

A
  • is inoculation continues after cells reach stationary phase, the cells will eventually die
  • typically much slower than exponential growth
  • re-adjust to dormant stage
  • viable cells remain for months or years
26
Q

Continuous culture

A

-an apen system, microbial culture of fixed volume

27
Q

Chemostat

A

-most common type of continuous culture device

28
Q

Dilution rate

A
  • F/V
  • F is the flow of adding fresh medium and removing spent medium
  • V is the culture volume
  • concentration of a limiting nutrient
  • both growth rate and population density of culture can be controlled independently and simultaneously
29
Q

Steady state

A
  • cell density and substrate concentration do not change over time
  • specific growth rate (D)= decrease in cell numbers due to dilution
  • experimental uses:
    • can maintain exponential growth phase for weeks/months
    • used for study physiology, microbial ecology and evolution, enriched and isolate of bacteria from nature
    • growth rate controlled by dilution rate
30
Q

Culture media

A
  • nutrient used to grow microbes in the laboratory

- typically sterilized in an autoclave

31
Q

Defined media

A

-exact chemical composition known

32
Q

Complex media

A

-composed of digests of microbial, animal, or plant products

33
Q

Enriched media

A
  • contain complex media plus highly nutritious materials

- used to culture fastidious (nutritionally demanding) microbes

34
Q

Selective media

A

-contain compounds that selectively inhibit growth of some microbes but not other

35
Q

Differential media

A

-contain an indicator, usually a dye, that detects particular metabolic but not during growth

36
Q

Microbes

A
  • sterilization of media is critical

- to prevent contamination, aseptic techniques should be followed

37
Q

Total cell count

A

-counting chambers with squares etched in a slide for liquid samples

38
Q

Microscopic cell count

A

-observing and enumerating cells present dried on slides or on liquid samples

39
Q

Limitations of microscopic cell counts

A
  • cannot distinguish between live vs dead cells without special stains
  • precision is difficult to achieve
  • phase-contrast microscope required if a stain is not used
  • cell suspensions of low density hard to count
  • motile cells need to immobilized
  • debris in sample can be mistaken for cells
40
Q

Microscopic cell counts in microbial ecology

A

-often used to natural samples
-use stains to visualize and provide phylogenetic information or metabolic properties
-DAPI (blue) reacts with DNA
-other fluorescent stains differentiate live and dead cells
phylogenetic stains can determine properties of bacteria and archaea

Microbiology Chapter 3 Microbial Metabolism (2 decks)

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