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Hilary Term 1 > Control of Prokaryotic Growth > Flashcards

Control of Prokaryotic Growth Flashcards

1
Q

Most bacterial cells divide via

A

binary fission

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2
Q

Describe binary fission

A
  • cell elongation
  • central septum formation
  • cell wall formation occurs intercalatorially
  • cells separate
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3
Q

Describe the products of binary fission

A

one bacterial cell has equal products under binary fission: 2 genetically identical daughter clones

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4
Q

Describe budding

A
  • simple budding
  • budding from hyphae
  • unequal products in division
  • cell wall formation is not intercalatory, but polar
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5
Q

Give examples of cells exhibiting simple budding

A
  • Pirellula
  • Blastobacter
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6
Q

Give examples of cells exhibiting budding from hyphae

A
  • Hyphomicrobium
  • Rhodomicrobium
  • Pedomicrobedium
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7
Q

Describe Caulobacter formation

A
  • relies on unequal products post-division
  • stalks produce differentiated swimmer cells while the stalk itself holds fast
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8
Q

What is Caulobacter

A

a stalked organism

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9
Q

Give an example of unequal products formation

A
  • when a cell undergoes polar growth without differentiation of cell size (without elongating first)
  • occurs in the Rhodopseudomonas, the Nitrobacter and the Methylosinus
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10
Q

What is the adaptation of efficient cell division in bacteria?

A

exponential growth

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11
Q

One bacterial cell can divide into … after 10 hours

A

1,048,576

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12
Q

How is bacterial growth rate calculated?

A
  • measure logarithmic cell abundance per ml against time
  • plotting this graphically to allow slope calculation (the rate of division)
  • can also calculate g
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13
Q

What is g, in terms of bacterial cell division?

A

the mean generation time (time taken for cell abundance to double)

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14
Q

Why does bacterial culture growth occur in stages?

A

Because exponential growth is not sustainable in vitro

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15
Q

Describe the experimental set up for investigating bacterial culture growth

A
  • culture inside of a culture vessel with room for a gaseous headspace
  • overflow collected
  • effluent microbial cells analysed
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16
Q

Describe the classification of stages of bacterial cell culture growth

A
  • lag
  • exponential
  • stationary
  • death phases
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17
Q

Describe the lag phase

A
  • post-incodulation
  • due to the change of growth conditions in minerals and nutrients
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18
Q

Describe the exponential phase

A
  • relatively short
  • where g is calculated
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19
Q

Describe exponential growth

A
  • requires very rich media
  • not always feasible
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20
Q

Describe the death phase

A
  • often protracted
  • can be replaced by a quiescent phase if resistance is horizontally acquired
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21
Q

How is bacterial abundance calculated?

A
  • the viable organism count
  • turbidity (via optical density)
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22
Q

Explain the inability of expontential growth to persist

A
  • nutrients are limiting
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23
Q

Describe bacterial culture growth on sugar

A
  • usually produce an acid
  • toxifies the product, limiting growth by mutation induction
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24
Q

Describe bacterial culture growth on organic acid

A

tends to alkalise the media, resulting in slowed or arrested growth

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25
How to set up experimentally to maximise the likelihood of prolonged exponential growth
- allow for fresh medium from a resevoir via a flow-rate regulatory mechanism - sterile air or other necessary metabolic gases
26
When measuring g
dilution rate is directly proportional to growth rate
27
Describe the minimum for bacterial temperature
- undergo membrane gelling - transport processes are so slow as to not facilitate growth
28
Describe bacteria at their optimum temperature
metabolism is at the maximum possible rate
29
Describe the maximum for bacterial temperature
- protein denaturation occurs - cytoplasmic membrane collapse - thermal lysis
30
Psychrophile Polaromonas vascuolata
optimum is 4 degrees Celsius
31
Mesophile Escherichia Coli
optimum is 39 degrees Celsius
32
Thermophile Geobacillus stearothermophilus
optimum is 60 degrees Celsius
33
Hyperthermophilic archaea Pyrolobus fumerii
optimum is 106 degrees Celsius
34
Describe Alkaliphiles
- prefer alkaline pHs (of greater than or equal to 8 - Chloroflexus aurantiacus - Bacillus firmus - archaea: Natronobacterium gregoryi
35
Describe Acidophiles
- prefer acidic pHs (lesser than 5.5) - Rhodopila globiformis - Acidithiobacillus ferrooxidans - archaea: Picrophilus oshimae
36
Describe Neutrophiles
- prefer central pHs (greater than 5.5, but lesser than 8) - E. Coli
37
Describe the acidic environments in which bacteria might dwell
- volcanic soils and waters - gastric fluids - citric fruits - mine drainage efflux
38
Alkaline examples are found in
- seawater - some lakes - limey environments
39
Why are buffers necessary?
to ensure the efficient and adequate growth of media cultures
40
What is osmolarity?
an organism’s sensitivity to sodium chloride
41
Describe Nonhalophiles
- those who do not tolerate any salt - E. Coli
42
Describe Halotolerance
- grow at lesser than 5 percentage NaCl - Staphylococcus aureus.
43
Describe Halophiles
- grow between 5 and 10 percent NaCl - Aliivibrio fischeri
44
Describe Extreme halophiles
- grow at greater than 15% NaCl - Halobacterium salinarum.
45
Describe the different categories of aerobicity
- obligate - facultative - microaerophilic
46
Describe obligate aerobes
- oxygen is required to complete aerobic respiration - Micrococcus luteus
47
List some frequent habitats for obligate anaerobes
- skin - dust particles
48
Describe facultative aerobes
- do not require oxygen - more efficient growth in its presence - undergo aerobic respiration, as well as anaerobic respiration and fermentation - E. Coli
49
Give a frequent habitat for facultative anaerobes
mammalian large intestine
50
Describe microaerophilic aerobes
- require oxygen at lower levels that atmospheric oxygen, so that they can complete aerobic respiration - Spirillum volutans
51
Give a frequent habitat for microaerophilic aerobes
lake water
52
Describe the classification of anaerobes
- aerotolerant - obligate
53
Describe aerotolerant anaerobes
- do not require a totally anoxic environment - do not require oxygen to complete fermentation pathways - Streptococcus pyrogenes
54
A frequent habitat for aerotolerant anaerobes is
the upper respiratory tract
55
Describe obligate anaerobes
- metabolise via anaerobic respiration or fermentation - find oxygenic presence either harmful or lethal - Methanobacterium formicicum
56
Frequent habitats for obligate anaerobes are
- sewage sludge - anoxic lake sediments
57
How are compatible solutes acquired?
intake or synthesis
58
Describe nonphototrophic bacteria
- associated with glutamate and proline, sucrose and tehalose - Escherichia
59
Describe freshwater cyanobacteria
- associated with glutamate and proline, sucrose and tehalose. - Anabaena
60
Describe the Halotolerants with respect to their compatible solutes
sucrose and tehalose
61
Marine cyanobacteria
- Synechococcus - associated with alpha-Glucosylglycerol
62
Marine algae
- Phaeocystis - associated with Mannitol, various glycosides and dimethylsulphoniopropionate
63
Describe Halophilic photorophic purple bacteria
- Halorhodospira - associated with Glycine betaine, ectoine and trehalose
64
Describe the Alphanothece
- salt lake cyanobacteria - associated with Glycine betaine
65
Describe extremely halophilic archaea
- Halobacterium - associated with potassium chloride
66
Describe Salinibacter
associated with potassium chloride
67
Describe Haloalkaliphilic archaea
- Natrinema - associated with potassium chloride
68
Describe Halophilic green algae
- Dunaliella - associated with glycerol
69
Describe the the Xerophilic and omsophilic yeasts
- Zygosachharomyces - associated with glycerol
70
Describe the Xerophilic filamentous fungi
- Xeromyces - associated with glycerol.
71
How do bacteria control growth?
recognising cell density
72
How do Gram negative bacteria recognise cell density?
- quorum sensing - activator protein activated by an AHL - interacts with the chromosomes to produce quorum-specific proteins - interacts with AHL synthase, producing further AHL - creates a self-amplifying feedforward loop
73
Describe AHLs
the group of intracellular esters acyl homoserine lactones
74
Describe a quorum
a level of high enough cell density
75
Describe quorum sensing
- synthesising AHLs of varying alkyl side chain length - activate gene expression once a quorum is reache - can be important for pathogenicity
76
Describe cell density recognition in the bioluminescent bacteira Aliivibrio fischeri
- AHLs control expression of the luxCDABE operon - AHL-binding to the lux regulator LuxR activates transcription of the lux inducer LuxI - once a quorum is reached, bioluminescence is switched on.
77
What is LuxI?
AHL synthase
78
How do Gram positive bacteria control growth?
using peptides
79
Describe the stringent response
- arises from cessation or downshift of prokaryotic growth - (p)ppGpp synthesis reduces tRNA and rRNA synthesis - activation of amino acid biosynthetic operons (if this is the factor behind growth halt) - cell division arrest - increases cellular stress responses
80
What generally causes cessation or downshift in prokaryotic growth
transfer from rich to a poor medium, oxygen mutation or carbon limitation
81
(p)ppGpp
guanine penta- or tetraphosphate
82
Describe the heat shock response
- several HSPs tasked with refolding denatured proteins - HSP70 preoccupied with refolding denatured proteins - leaving RpoH sigma factor to accumulate and complete its function of heat shock gene transcription
83
HSPs
- Heat Shock Proteins - e.g. HSP60, HSP10
84
HSP60
also known as GroEL
85
HSP10
also termed GroES
86
HSP70
- also known as DnaK - degrades RpoH sigma factor
87
Describe the amino acid starvation pathway
under amino acid starvation, injured tRNAs bind to the ribosome and stall their tRNA and RRNA synthesis

Hilary Term 1 (61 decks)

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