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Michaelmas Term 1 > Small is beautiful: challenges and consequences of life at the molecular level > Flashcards

Small is beautiful: challenges and consequences of life at the molecular level Flashcards

1
Q

Describe unicellular life

A

interact directly with their environment, over which have limited control

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2
Q

Describe cardinal temperatures

A

for every microorganism there is:
- a minimum temperature below which growth is not possible
- an optimum temperature at which growth is most rapid
- a maximum temperature above which growth is not possible

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3
Q

Describe membrane gelling

A

transport processes so slow that growth cannot occur

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4
Q

Describe protein denaturation

A
  • collapse of the cytoplasmic membrane
  • thermal lysis
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5
Q

Describe mesophiles

A
  • best studied and understood
  • occur in the digestive tract of animals
  • in terrestrial and aquatic environments in temperate and tropical latitudes.
  • Escherichia coli
  • most bacteria associated with humans
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6
Q

Describe E. coli

A

– optimum temperature for most E.coli: ~39 degreesC
– maximum is 48 degreesC
- minimum 8 degreesC
– temperature range: ~40 degreesC.

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7
Q

List some mesophilic bacteria

A

– Staphylococcus aureus
– Streptococcus pyogenes
– Neisseria meningitidis

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8
Q

Describe Psychrophiles

A
  • optimal growth temperature of <15 degreesC or lower
  • maximum growth temperature <20 degreesC
  • minimum growth temperature of 0 degreesC or lower
  • found in constantly cold environments
  • often intolerant to warmer temperatures
  • frequently grow in dense masses within and under sea ice in polar regions
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9
Q

Describe Psychrotolerant microbes

A
  • can grow at 0 degreesC
  • have optima of 20-40 degreesC
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10
Q

Describe Psychrophilic adaptations

A
  • enzymes that function optimally in the cold
  • high content of unsaturated and short chain fatty acids
  • express Cold shock proteins
  • express Cryoprotectants
  • exopolysaccharide cell surface slime
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11
Q

Describe Thermophiles

A

growth temperature optima: >45 degrees C

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12
Q

Describe Hyperthermophiles

A

growth temperature optima: >80 degrees C

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13
Q

Describe the environments of Thermophiles and Hyperthermophiles

A

– terrestrial hot springs: >100 degrees C
– hydrothermal vents: >350 degrees C

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14
Q

Describe Methanopyrus

A
  • methane procuring genus of archaea
  • capable of growth up to 122 degrees C
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15
Q

Describe some adaptations to extreme heat

A
  • genomic changes
  • base biases
  • gene expression
  • protein thermostability
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16
Q

Describe the genomic changes of Thermophiles and Hyperthermophiles

A
  • genes gained through HGT
  • mutations
  • genome reduction
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17
Q

Describe the base biases of Thermophiles and Hyperthermophiles

A
  • highly stable gene structure
  • high GC content (not universal)
  • codon use biases
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18
Q

Describe the gene expression of Thermophiles and Hyperthermophiles

A
  • stable and efficient protein synthesis
  • temperature responses of gene expression
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19
Q

Describe the protein thermostability of Thermophiles and Hyperthermophiles

A
  • more disulphide bonds
  • stability of protein
    complices
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20
Q

Describe reproduction by binary fission - the basics

A
  • rapid
  • efficient
  • adapted for processes such as sporulation
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21
Q

Describe reproduction by binary fission - the specifics

A
  • cell elongation
  • genome replication
  • separation of genomes
  • formation of cleavage furrow
  • cell wall forms in cleavage furrow
  • septation
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22
Q

septation

A

separation

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23
Q

Describe some features of binary fission

A
  • generates identical daughter cells,
  • exponential growth (geometric increase in numbers)
  • multiple genome replications per cell division (speeds up division rate)
  • ‘feast and famine’ lifestyle
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24
Q

Describe E. coli division

A

A single Escherichia coli cell dividing every 33.3 minutes without nutrient limitation could reach the mass of the earth in less than 48 hours.

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25
Q

Describe the limitations to microbial size

A
  • SA:V gets smaller as the cell gets larger,
  • if a cell becomes too large, insufficient material can cross the membrane fast enough
  • cell must divide to maintain favourable SA:V
  • cell must maintain sufficient genetic and metabolic capacity to function
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26
Q

Describe rod-shaped bacterial size

A
  • alter both their width and length to achieve a condition-dependent surface
  • maintenance of a condition-dependent SA:V sets bacterial size.
  • rates of volume and surface growth both scale with volume, producing SA:V homeostasis
  • surface material accumulation threshold for division could underlie length control
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27
Q

… links surface growth rate to volume (in rod-shaped bacteria)

A

Biosynthesis of surface material in the cytoplasm

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28
Q

Define exponential volumetric growth

A

dV/dt alpha V

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29
Q

Define surface growth rate scaling with volume

A

dA/dt alpha V

30
Q

if surface synthesis > volume synthesis

A

cell is smaller on average

31
Q

if volume synthesis > surface synthesis

A

cell is larger on average

32
Q

Describe nano- bacteria and archaea

A
  • ‘filterable’
  • 50-400nm
  • abundant in biosphere
  • oceans,riversand soils.
  • mostly uncultured & characterised
  • many likely non-cultivable
  • very small genomes
  • dependent on communities
33
Q

Describe LSB

A
  • large sulfur bacteria
  • e.g. Thiomargarita magnifica
34
Q

Describe Thiomargarita magnifica

A
  • found attached to leaves in sulphur-rich waters in
    mangrove swamps in Guadeloupe
  • almost 1cm
  • large vacuole
  • cytoplasmic layer only 2-3μm thick
  • polypoid (~40,000 genome copies)
  • grow relatively slowly
  • two weeks to produce daughter cells
35
Q

Describe the advantages of polyploidy

A

– enables local transcription and translation
- occurs in specialised Pepin structures

36
Q

Describe the Gram-positive cell wall

A
  • glycan chain
  • S-layer glycoproteins
  • peptidoglycan
  • cytoplasmic membrane
  • lipoteichoic acid
  • teichoic acid
  • polysaccharide
  • lipoprotein
  • cytoplasm
37
Q

Describe the Gram-negative cell wall

A
  • porins
  • LPS
  • outer membrane
  • peptidoglycan
  • lipoprotein
  • periplasm
  • cytoplasmic membrane
  • cytoplasm
38
Q

Describe the cell envelope of Sulfolobales

A

S-layer

39
Q

Describe the cell envelope of Ignicoccus hospitalis

A
  • outer membrane
  • Ihomp1
  • 24nm pore
40
Q

Describe the cell envelope of Methanosphaera

A

pseudomurein

41
Q

Describe the cell envelope of Methanothermus

A
  • S-layer
  • pseudomurein
42
Q

Describe the cell envelope of Methanospirillum

A
  • sheath
  • S-layer
43
Q

Describe the cell envelope of Methanosarcina

A
  • methanochondriotin
  • S-layer
44
Q

Describe the bacterial cytoplasmic membrane

A
  • 6-8 nm
  • separates cytoplasm from the environment
  • nutrients must be transported inwards, waste products outwards
45
Q

Describe the pmf

A
  • consequence of the electrochemical gradient across the membrane
  • major source of energy transduction, including active transport ant ATP generation
46
Q

Describe the roles of the cytoplasmic membrane in bacteria

A
  • free energy source
  • signalling and processing
  • antibiotic resistance
  • pH homeostasis
  • cell division
  • dynamic communication
  • membrane transport
  • ATP synthesis
  • motility
47
Q

Describe phototrophy

A

organism uses light as the energy source to catalyse biochemical reactions

48
Q

Describe chemotrophy

A

organism uses chemical reactions (oxidation) as the energy source to catalyse biochemical reactions

49
Q

Describe autotrophy

A

organism is capable of fixing carbon from non-biological (inorganic) sources.

50
Q

Describe heterotrophy

A

organism must obtain carbon from biological sources.

51
Q

List some methods of microbial motility

A
  • swimming
  • twitching
  • gliding
  • sliding
52
Q

Describe sliding

A

movement by growth on a surface.

53
Q

Describe the microbial motile environment

A
  • viscous environment
  • subject to molecular forces leading to Brownian movement
54
Q

Describe bacterial swimming

A

individually and in swarms

55
Q

Describe bacterial twitching

A

mediated by pilus retraction

56
Q

Describe bacterial gliding

A

active movement across a surface

57
Q

Describe the flagella

A
  • one or more
  • allow bacteria to swim
  • originate in the cytoplasm beneath the cell wall
  • extend beyond the cell
58
Q

Describe monotrichy

A
  • single flagellum at one pole
  • e.g. Vibrio cholerae
59
Q

Describe amphitrichy

A
  • presence of a single flagella at each pole
  • e.g. Spirilum
60
Q

Describe lophotrichy

A
  • tuft of flagella at one pole
  • e.g. Pseudomonas
61
Q

Describe peritrichy

A
  • flagella all over the surface
  • e.g. E. coli
62
Q

Non-motile bacteria that lack a flagella are called

A

atrichous

63
Q

How to bacteria avoid unfavourable environments

A

resting stages

64
Q

Describe endospory

A

produced by Gram positive bacteria

65
Q

Describe Gram positive endospores

A
  • highly resistant to heat, desiccation and radiation
  • stable for many years, decades, perhaps centuries
  • major reason for difficulties in sterilisation processes
  • important in medicine and the food industry
66
Q

Describe the bacterial vegetative cycle

A
  • growth
  • medial division
67
Q

Describe bacterial sporulation

A
  • polar division (prespore and septum, mother cell)
  • asymmetric cell division
  • engulfment
  • cortex (+ cell wall and membrane)
  • spore coat
  • maturation and cell lysis
  • germination
68
Q

Describe biofilms

A
  • association with surfaces forming biofilms
  • composed of single microbes or complex communities
  • various relationships, antagonistic, cooperative, or neutral
  • complex biological processes: crucibles of evolution
69
Q

Describe biofilm formation

A
  • reversible attachment to surface
  • irreversible attachment
  • maturation: EPS and cell cluster
  • microcolonies
  • dispersion
70
Q

Microbes exhibit

A

little or no homeostasis.

71
Q

Name some factors microbes have to tradeoff

A

size, metabolic & genetic complexity, and growth rate.

Michaelmas Term 1 (42 decks)

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