Small is beautiful: challenges and consequences of life at the molecular level Flashcards
(71 cards)
1
Q
Describe unicellular life
A
interact directly with their environment, over which have limited control
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
3
Q
Describe membrane gelling
A
transport processes so slow that growth cannot occur
4
Q
Describe protein denaturation
A
- collapse of the cytoplasmic membrane
- thermal lysis
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
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.
7
Q
List some mesophilic bacteria
A
– Staphylococcus aureus
– Streptococcus pyogenes
– Neisseria meningitidis
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
9
Q
Describe Psychrotolerant microbes
A
- can grow at 0 degreesC
- have optima of 20-40 degreesC
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
11
Q
Describe Thermophiles
A
growth temperature optima: >45 degrees C
12
Q
Describe Hyperthermophiles
A
growth temperature optima: >80 degrees C
13
Q
Describe the environments of Thermophiles and Hyperthermophiles
A
– terrestrial hot springs: >100 degrees C
– hydrothermal vents: >350 degrees C
14
Q
Describe Methanopyrus
A
- methane procuring genus of archaea
- capable of growth up to 122 degrees C
15
Q
Describe some adaptations to extreme heat
A
- genomic changes
- base biases
- gene expression
- protein thermostability
16
Q
Describe the genomic changes of Thermophiles and Hyperthermophiles
A
- genes gained through HGT
- mutations
- genome reduction
17
Q
Describe the base biases of Thermophiles and Hyperthermophiles
A
- highly stable gene structure
- high GC content (not universal)
- codon use biases
18
Q
Describe the gene expression of Thermophiles and Hyperthermophiles
A
- stable and efficient protein synthesis
- temperature responses of gene expression
19
Q
Describe the protein thermostability of Thermophiles and Hyperthermophiles
A
- more disulphide bonds
- stability of protein
complices
20
Q
Describe reproduction by binary fission - the basics
A
- rapid
- efficient
- adapted for processes such as sporulation
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
22
Q
septation
A
separation
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
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.
25
Describe the limitations to microbial size
- 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
26
Describe rod-shaped bacterial size
- 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
27
... links surface growth rate to volume (in rod-shaped bacteria)
Biosynthesis of surface material in the cytoplasm
28
Define exponential volumetric growth
dV/dt alpha V
29
Define surface growth rate scaling with volume
dA/dt alpha V
30
if surface synthesis > volume synthesis
cell is smaller on average
31
if volume synthesis > surface synthesis
cell is larger on average
32
Describe nano- bacteria and archaea
- ‘filterable’
- 50-400nm
- abundant in biosphere
- oceans,riversand soils.
- mostly uncultured & characterised
- many likely non-cultivable
- very small genomes
- dependent on communities
33
Describe LSB
- large sulfur bacteria
- e.g. Thiomargarita magnifica
34
Describe Thiomargarita magnifica
- 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
Describe the advantages of polyploidy
– enables local transcription and translation
- occurs in specialised Pepin structures
36
Describe the Gram-positive cell wall
- glycan chain
- S-layer glycoproteins
- peptidoglycan
- cytoplasmic membrane
- lipoteichoic acid
- teichoic acid
- polysaccharide
- lipoprotein
- cytoplasm
37
Describe the Gram-negative cell wall
- porins
- LPS
- outer membrane
- peptidoglycan
- lipoprotein
- periplasm
- cytoplasmic membrane
- cytoplasm
38
Describe the cell envelope of Sulfolobales
S-layer
39
Describe the cell envelope of Ignicoccus hospitalis
- outer membrane
- Ihomp1
- 24nm pore
40
Describe the cell envelope of Methanosphaera
pseudomurein
41
Describe the cell envelope of Methanothermus
- S-layer
- pseudomurein
42
Describe the cell envelope of Methanospirillum
- sheath
- S-layer
43
Describe the cell envelope of Methanosarcina
- methanochondriotin
- S-layer
44
Describe the bacterial cytoplasmic membrane
- 6-8 nm
- separates cytoplasm from the environment
- nutrients must be transported inwards, waste products outwards
45
Describe the pmf
- consequence of the electrochemical gradient across the membrane
- major source of energy transduction, including active transport ant ATP generation
46
Describe the roles of the cytoplasmic membrane in bacteria
- free energy source
- signalling and processing
- antibiotic resistance
- pH homeostasis
- cell division
- dynamic communication
- membrane transport
- ATP synthesis
- motility
47
Describe phototrophy
organism uses light as the energy source to catalyse biochemical reactions
48
Describe chemotrophy
organism uses chemical reactions (oxidation) as the energy source to catalyse biochemical reactions
49
Describe autotrophy
organism is capable of fixing carbon from non-biological (inorganic) sources.
50
Describe heterotrophy
organism must obtain carbon from biological sources.
51
List some methods of microbial motility
- swimming
- twitching
- gliding
- sliding
52
Describe sliding
movement by growth on a surface.
53
Describe the microbial motile environment
- viscous environment
- subject to molecular forces leading to Brownian movement
54
Describe bacterial swimming
individually and in swarms
55
Describe bacterial twitching
mediated by pilus retraction
56
Describe bacterial gliding
active movement across a surface
57
Describe the flagella
- one or more
- allow bacteria to swim
- originate in the cytoplasm beneath the cell wall
- extend beyond the cell
58
Describe monotrichy
- single flagellum at one pole
- e.g. Vibrio cholerae
59
Describe amphitrichy
- presence of a single flagella at each pole
- e.g. Spirilum
60
Describe lophotrichy
- tuft of flagella at one pole
- e.g. Pseudomonas
61
Describe peritrichy
- flagella all over the surface
- e.g. E. coli
62
Non-motile bacteria that lack a flagella are called
atrichous
63
How to bacteria avoid unfavourable environments
resting stages
64
Describe endospory
produced by Gram positive bacteria
65
Describe Gram positive endospores
- 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
Describe the bacterial vegetative cycle
- growth
- medial division
67
Describe bacterial sporulation
- polar division (prespore and septum, mother cell)
- asymmetric cell division
- engulfment
- cortex (+ cell wall and membrane)
- spore coat
- maturation and cell lysis
- germination
68
Describe biofilms
- 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
Describe biofilm formation
- reversible attachment to surface
- irreversible attachment
- maturation: EPS and cell cluster
- microcolonies
- dispersion
70
Microbes exhibit
little or no homeostasis.
71
Name some factors microbes have to tradeoff
size, metabolic & genetic complexity, and growth rate.
