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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
Q

How to set up experimentally to maximise the likelihood of prolonged exponential growth

A
  • allow for fresh medium from a resevoir via a flow-rate regulatory mechanism
  • sterile air or other necessary metabolic gases
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26
Q

When measuring g

A

dilution rate is directly proportional to growth rate

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27
Q

Describe the minimum for bacterial temperature

A
  • undergo membrane gelling
  • transport processes are so slow as to not facilitate growth
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28
Q

Describe bacteria at their optimum temperature

A

metabolism is at the maximum possible rate

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29
Q

Describe the maximum for bacterial temperature

A
  • protein denaturation occurs
  • cytoplasmic membrane collapse
  • thermal lysis
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30
Q

Psychrophile Polaromonas vascuolata

A

optimum is 4 degrees Celsius

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31
Q

Mesophile Escherichia Coli

A

optimum is 39 degrees Celsius

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32
Q

Thermophile Geobacillus stearothermophilus

A

optimum is 60 degrees Celsius

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33
Q

Hyperthermophilic archaea Pyrolobus fumerii

A

optimum is 106 degrees Celsius

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34
Q

Describe Alkaliphiles

A
  • prefer alkaline pHs (of greater than or equal to 8
  • Chloroflexus aurantiacus
  • Bacillus firmus
  • archaea: Natronobacterium gregoryi
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35
Q

Describe Acidophiles

A
  • prefer acidic pHs (lesser than 5.5)
  • Rhodopila globiformis
  • Acidithiobacillus ferrooxidans
  • archaea: Picrophilus oshimae
36
Q

Describe Neutrophiles

A
  • prefer central pHs (greater than 5.5, but lesser than 8)
  • E. Coli
37
Q

Describe the acidic environments in which bacteria might dwell

A
  • volcanic soils and waters
  • gastric fluids
  • citric fruits
  • mine drainage efflux
38
Q

Alkaline examples are found in

A
  • seawater
  • some lakes
  • limey environments
39
Q

Why are buffers necessary?

A

to ensure the efficient and adequate growth of media cultures

40
Q

What is osmolarity?

A

an organism’s sensitivity to sodium chloride

41
Q

Describe Nonhalophiles

A
  • those who do not tolerate any salt
  • E. Coli
42
Q

Describe Halotolerance

A
  • grow at lesser than 5 percentage NaCl - Staphylococcus aureus.
43
Q

Describe Halophiles

A
  • grow between 5 and 10 percent NaCl
  • Aliivibrio fischeri
44
Q

Describe Extreme halophiles

A
  • grow at greater than 15% NaCl
  • Halobacterium salinarum.
45
Q

Describe the different categories of aerobicity

A
  • obligate
  • facultative
  • microaerophilic
46
Q

Describe obligate aerobes

A
  • oxygen is required to complete aerobic respiration
  • Micrococcus luteus
47
Q

List some frequent habitats for obligate anaerobes

A
  • skin
  • dust particles
48
Q

Describe facultative aerobes

A
  • do not require oxygen
  • more efficient growth in its presence
  • undergo aerobic respiration, as well as anaerobic respiration and fermentation
  • E. Coli
49
Q

Give a frequent habitat for facultative anaerobes

A

mammalian large intestine

50
Q

Describe microaerophilic aerobes

A
  • require oxygen at lower levels that atmospheric oxygen, so that they can complete aerobic respiration
  • Spirillum volutans
51
Q

Give a frequent habitat for microaerophilic aerobes

A

lake water

52
Q

Describe the classification of anaerobes

A
  • aerotolerant
  • obligate
53
Q

Describe aerotolerant anaerobes

A
  • do not require a totally anoxic environment
  • do not require oxygen to complete fermentation pathways
  • Streptococcus pyrogenes
54
Q

A frequent habitat for aerotolerant anaerobes is

A

the upper respiratory tract

55
Q

Describe obligate anaerobes

A
  • metabolise via anaerobic respiration or fermentation
  • find oxygenic presence either harmful or lethal
  • Methanobacterium formicicum
56
Q

Frequent habitats for obligate anaerobes are

A
  • sewage sludge
  • anoxic lake sediments
57
Q

How are compatible solutes acquired?

A

intake or synthesis

58
Q

Describe nonphototrophic bacteria

A
  • associated with glutamate and proline, sucrose and tehalose
  • Escherichia
59
Q

Describe freshwater cyanobacteria

A
  • associated with glutamate and proline, sucrose and tehalose.
  • Anabaena
60
Q

Describe the Halotolerants with respect to their compatible solutes

A

sucrose and tehalose

61
Q

Marine cyanobacteria

A
  • Synechococcus
  • associated with alpha-Glucosylglycerol
62
Q

Marine algae

A
  • Phaeocystis
  • associated with Mannitol, various glycosides and dimethylsulphoniopropionate
63
Q

Describe Halophilic photorophic purple bacteria

A
  • Halorhodospira
  • associated with Glycine betaine, ectoine and trehalose
64
Q

Describe the Alphanothece

A
  • salt lake cyanobacteria
  • associated with Glycine betaine
65
Q

Describe extremely halophilic archaea

A
  • Halobacterium
  • associated with potassium chloride
66
Q

Describe Salinibacter

A

associated with potassium chloride

67
Q

Describe Haloalkaliphilic archaea

A
  • Natrinema
  • associated with potassium chloride
68
Q

Describe Halophilic green algae

A
  • Dunaliella
  • associated with glycerol
69
Q

Describe the the Xerophilic and omsophilic yeasts

A
  • Zygosachharomyces
  • associated with glycerol
70
Q

Describe the Xerophilic filamentous fungi

A
  • Xeromyces
  • associated with glycerol.
71
Q

How do bacteria control growth?

A

recognising cell density

72
Q

How do Gram negative bacteria recognise cell density?

A
  • 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
Q

Describe AHLs

A

the group of intracellular esters acyl homoserine lactones

74
Q

Describe a quorum

A

a level of high enough cell density

75
Q

Describe quorum sensing

A
  • synthesising AHLs of varying alkyl side chain length
  • activate gene expression once a quorum is reache
  • can be important for pathogenicity
76
Q

Describe cell density recognition in the bioluminescent bacteira Aliivibrio fischeri

A
  • 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
Q

What is LuxI?

A

AHL synthase

78
Q

How do Gram positive bacteria control growth?

A

using peptides

79
Q

Describe the stringent response

A
  • 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
Q

What generally causes cessation or downshift in prokaryotic growth

A

transfer from rich to a poor medium, oxygen mutation or carbon limitation

81
Q

(p)ppGpp

A

guanine penta- or tetraphosphate

82
Q

Describe the heat shock response

A
  • 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
Q

HSPs

A
  • Heat Shock Proteins
  • e.g. HSP60, HSP10
84
Q

HSP60

A

also known as GroEL

85
Q

HSP10

A

also termed GroES

86
Q

HSP70

A
  • also known as DnaK
  • degrades RpoH sigma factor
87
Q

Describe the amino acid starvation pathway

A

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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