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Microbiology > ch 7 bacterial and archaeal growth > Flashcards

ch 7 bacterial and archaeal growth Flashcards

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1
Q

binary fission

A

type of cell decision where the cell elongates as new cell envelope material is synthesized, nucleoid must replicate and partitioned in half, septum splits cell in half

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2
Q

cell cycle

A

the complete sequence of events extending from formation of a new cell through the next cell division
3 phases:
- initial growth
- chromosome replication and partitioning
- cytokinesis, during which a septum and daughter cells are formed

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3
Q

origin of replication

A

site at which replication begins

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4
Q

replisome

A

DNA synthesizing machinery

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5
Q

steps of septation

A

process of forming a cross wall btw two daughter cells
1. selection of the site where the septum will form
2. assembly of the Z-ring, which is a polymer of the cytoskeletal protein FtsZ
3. assembly of the machinery for synthesis of peptidoglycan and other cell wall constituents
4. constriction of the cell and septum formation

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6
Q

divisome formation

A

z-ring associates discontinuously at mid-cell
FtsZ filaments attach to the plasma membrane through anchoring proteins, which also coordinate the enzymes that synthesize and remodel peptidoglycan in the developing septum

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7
Q

cellular growth and determination of cell shape

A

after the cell is born, it enters growth where a single cell increases in size
cell shape is strict and passed on through generations
some microbes change shape under certain circumstances

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8
Q

cocci cell shape

A

cellular location of peptidoglycan synthesis determines coccus shape

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9
Q

rod and curved cell shape

A

rod: elongasome - MreB is scaffolded, creates filaments along cytoplasmic face of plasma membrane; growth occurs in numerous bands around the cell, not at the poles
curved: crescentin - localized to one side of the cell, resulting in asymmetric cell wall and vibroid shape

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10
Q

batch culture

A

incubated in a closed vessel with a single batch of medium

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11
Q

five phases of growth

A
  1. lag phase
  2. exponential phase
  3. stationary phase
  4. death phase
  5. long-term stationary phase
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12
Q

lag phase

A

when microorganisms are introduced into fresh culture medium and no immediate increase in cell number occurs
- cells are synthesizing new components
- replenish spent materials
- adapt to new medium or conditions

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13
Q

exponential phase

A

microorganisms grow and divide at the maximal rate possible given their genetic potential, the nature of the medium, and the environmental conditions

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14
Q

stationary phase

A

in a closed system, population growth eventually ceases and the growth curve becomes horizontal
- total number of viable cells remain constant
- balance btw cell division and cell death
- bc of nutrient limitation, limited oxygen, toxic waste accumulation, critical population density reached

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15
Q

death phase

A

number of viable cells declines exponentially, with the cells dying at a constant rate
- nutrient deprivation and the buildup of toxic wastes cause irreparable harm to the cells

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16
Q

long-term stationary phase

A

bacterial population continually evolves so that actively reproducing cells are those best able to use the nutrients released by their dying brethren and best able to tolerate the accumulated toxins
- process marked by successive waves of genetically distinct variants
- natural selection occurs within a single culture

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17
Q

mechanosensitive channels

A

mechanisms to protect the cell from changing osmotic concentrations
in a hypotonic solution, the membrane stretches due to an increase in hydrostatic pressure and cellular swelling. MS channels then open and allow solute to leave, protecting the cell from bursting

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18
Q

osmophiles

A

microbes adapted to extreme hypertonic solutions
- halophiles - require presence of NaCl at a conc above 0.2M

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19
Q

water activity (aw)

A

measure of the degree of water availability
equal to the ratio of solution’s vapor pressure to that of pure water
- most grow well at 0.98

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20
Q

osmotolerant

A

microorganisms that can grow over a wide range of water activity but optimally at higher levels

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21
Q

xerotolerant

A

microbes that withstand high solute concs
- can preserve dessication

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22
Q

cardinal temps

A

minimum, optimum, and maximum growth temps

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23
Q

five types of relationships to O2

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A
  1. obligate aerobe - requires O2
  2. obligate anaerobe - usually killed in presence of O2
  3. microaerophile - require 2 tp 10% O2
  4. facultative anaerobes - do not require O2 but grow better in its presence
  5. aerotolerant anaerobes - grow with or without O2
24
Q

barotolerant

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A

adversely affected by inc pressure, but not as severely as nontolerant organisms

25
barophilic
requires high pressure for growth
26
sunlight
major radiation source on earth
27
eutrophic
nutrient rich environments
28
oligotrophic
low nutrient environments
29
growth arrest
stationary phase microbes are not actively dividing, nor are they dead they are stressed by lack of nutrients or by deviation from optimal conditions
30
viable but not culturable state (VBNC)
the transient inability to grow under conditions that previously permitted routine growth may happen after an extended time in growth arrest
31
persisters
have the ability to survive exposure to an antibiotic even though they do not harbor antibiotic resistance genes characterized by low ATP levels
32
sessile
microbes found on surfaces
33
planktonic
microbes that are free floating
34
biofilm
slime-encased communities of microbes found everywhere in nature
35
extracellular polymeric substances (EPS)
carb and nucleic acid polymers secreted by biofilm bacteria that comprise the biofilm matrix include polysaccharides, proteins, glycoproteins, glycolipids, DNA
36
steps of biofilm formation
1. substratum preconditioning by ambient molecules 2. cell deposition 3. cell adsorption 4. desorption 5. cell-to-cell signaling and onset of exopolymer production 6. convective and diffusive transport of O2 and nutrients 7. replication and growth 8. secretion of polysaccharide matrix 9. detachment, erosion, and sloughing
37
emergent properties
population has properties that could not be predicted from studying its component single cells - - biofilms - interactions occur among the attached organisms, use molecules to communicate and DNA uptake can occur
38
quorum sensing
the process in which bacteria monitor their own population density or the presence of other species of bacteria by sensing the levels of signal molecules
39
autoinducer
a small molecule that induces synthesis of the enzyme responsible for the autoinducer's synthesis - N-acyl homoserine lactone (AHL) moves across the plasma membrane from the cytoplasm to the outside of the cell when cell population is high, AHL diffuses in the cell which induces specific gene expression (virulence factors, light)
40
culture medium
solid or liquid mixture of nutrients and other compounds used to grow, transport, and store microorganisms
41
defined/synthetic medium
each ingredient can be described with a chemical formula
42
complex media
contain at least one ingredient of nonspecific chemical composition such as peptones, meat extract, or yeast extract
43
supportive media
sustain growth of many types of microorganisms ex. tryptic soy broth, tryptic agar
44
enriched media
when other nutrients are added to supportive media to encourage the growth ex. blood
45
selective media
allow the growth of particular microorganisms, while inhibiting the growth of others ex. gram-negative grow on media containing bile salts or dyes, gram-positive is inhibited
46
differential media
distinguish among different groups of microbes and even permit tentative identification of microorganisms based on their biological characteristics
47
goal of streak plate
obtain individual cells that are separated from each other
48
why/when is a pour plate useful
when sampling a heterogeneous population of microbes, some of which might produce colonies that overgrow an agar surface if isolated by the streak or spread plate method
49
culturomics
use mini cultures and robotics to formulate many types of media and incubate in many different conditions to find the best one
50
direct counts
- counting chamber easy, inexpensive, quick gives info about size and morphology - membrane filter technique microbes filtered then stained with fluorescence - flow cytometry creates a stream of cells that one cell at a time passes through a beam of laser light - electronic counters coulter counter - microbe suspension of forced through a small hole, counted by electrical current flow
51
colony forming units (CFU)
the number of microorganisms that form colonies when cultures using spread plates or pour plates, an indication of the number of viable microorganisms in a sample
52
membrane filter method
bacteria from aquatic samples are trapped on membranes, soaked in culture media, then grown colony count determines number of bacteria in sample
53
method of measuring cell mass
dry weight - cells from liquid culture are pelleted by centrifugation and weighed spectrophotometry - amount of scattering is directly proportional to the biomass of cell present and indirectly related to cell number
54
continuous culture system
method of growing microorganisms in a system with constant environmental conditions maintained by supplying nutrients and removing wastes allow study of microbial growth at very low nutrient concs, close to those present in natural environment
55
chemostat
method of continuous culture system rate of incoming medium = rate of removal of medium most stable and effective at lower dilution rates
56
turbidostat
continuous culture system regulates flow rate of media through vessel to maintain predetermined turbidity maintains a desired cell density dilution rate varies, contains all nutrients in excess best at high dilution rates

Microbiology (13 decks)

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