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Physiology of Microbes > Temperature stress and Osmoregulation L9 > Flashcards

Temperature stress and Osmoregulation L9 Flashcards

1
Q

what happens when temperature changes

A

chemical and enzymatic reactions change
- faster rates at higher temperatures
- slower rates at lower temperatures
growth rates change

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2
Q

what is an arrhenius plot used for

A

describe the relationship between growth rate and growth temperature

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3
Q

effect of temperature on microbes growth

A

Can cool microbes to a point where stop growing, if warm them up again will grow again

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4
Q

what occurs at minimum growth rate

A

membrane gelling

transport processes slow so growth cant occur

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5
Q

what occurs between minimum and optimum growth rate

A

enzymes and reactions occurring at increasingly rapid rate

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6
Q

what occurs at optimum growth rate

A

enzymes and reactions occurring at maximal possible rate

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7
Q

what occurs at maximum growth rate

A

protein denaturation, collapse of cytoplasmic membrane, thermal lysis

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8
Q

in frozen water what grows

A

nothing as microbes need water to grow

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9
Q

what is a psychotroph

A

organism that has an extended growth range

can adapt to extremes of temperature by changing cellular processes

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10
Q

what does each single stress response induce

A

specific set of stress proteins

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11
Q

what are stress responses controlled by

A

alternative sigma factors

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12
Q

what happens if stress response genes induced

A

helps cell repair any damage and adapt to new temperature

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13
Q

what happens to the cell after heat shock occurs

A

major damage - proteins denatured
macromolecular complexes dissociate e.g. ribosome
individual cell proteins denatured

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14
Q

how does cell respond to high temperature stress

A

inducing synthesis of heat shock proteins (Hsps)

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15
Q

what are heat shock proteins function

A

role in getting proteins to fold correctly

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16
Q

how do proteins fold

A

not all proteins fold spontaneously inside bacterial cells

~30% need assist

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17
Q

what do proteins that cant fold need

A

chaperone

heat shock proteins are chaperones

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18
Q

what are the two major groups of heat shock proteins - chaperones

A

20% need DnaJ and DnaK

10-15% also need GroES and GroEL

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19
Q

what happens in response to heat shock

A

needs more heat shock proteins and other new gene products

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20
Q

what prevents heat shock gene production

A

DnaK normally binds to sigma 32 and prevents it binding to promoter to express heat shock genes

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21
Q

what happens to the unused sigma 32

A

targeted for degradation by protease FtsH

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22
Q

what happens when heat shock occurs

A

DnaK now needed in cell to bind to denatured proteins

releases sigma 32 and heat shock proteins induced

23
Q

when is sigma 32 made

A

sigma 32 always present in cell

24
Q

what happens to DnaK under normal conditions

A

DnaK targeted, picked up by DnaJ sent to FtsH, gets broken down

25
Q

what happens when DnaK and DnaJ release sigma 32

A

can interact with RNAP and switch on heat shock genes

26
Q

how does osmoregulation effect the cell

A

Turgor pressure controlled by adjusting total osmotic solute pool
Solute accumulation /efflux is central to control
Many different cellular systems involved

27
Q

what is the most abundant cation in bacteria cytoplasm

A

potassium

28
Q

when does potassium concentration increase

A

following hyperosmotic shock

29
Q

what effects potassium concentration

A

adaptive process so must be reversible

30
Q

what causes potassium influx

A

response to increasing osmolarity = trk, kdp

31
Q

what causes potassium efflux

A

response to reducing osmolarity = kdpB, kdpC

32
Q

what operon controls potassium efflux

A

Encoded by kdpFABC operon

33
Q

what REGULATES potassium efflux

A

KdpD and KdpE = “2 component response regulator”

34
Q

where is KdpD

A

inner membrane protein of E. coli

35
Q

what is KdpD

A

autophosphorylating sensing protein

cytoplasmic regulator protein

36
Q

what happens in Kdp regulation

A

periplasm proteins change shape in response to potassium concentration
- if potassium conc low = protein on outside in periplasm changes shape = protein picks up a phosphate group from ATP = autophosphoprylation
phosphate transferred to KdpE protein (in cytoplasm)
KdpE-phosphate binds to kdpFABC operon promoter

37
Q

when is the kdpFABC operon activated

A

Switch on in response to potassium depletion outside cell

38
Q

wat happens in kdpFABC operon when high enough potassium

A

signal goes away

reset system in response to environment

39
Q

what are porins function

A

allow diffusion of small polar molecules across OM of Gram-negative bacteria
Allow bulk transport across lipids

40
Q

what are the two major porins produced

A

OmpF

OmpC

41
Q

how do the porins differ

A 
OmpF = 1.16 nm pore allows rapid diffusion of molecules
OmpC = 1.08 nm excludes bile salts & allows slower diffusion of molecules
42
Q

In human gut where high solute concentration present which omp is made

A

OmpC produced -bile cant get through

Small regulatory proteins involved in controlling this switch

43
Q

what is the pro of small porins

A

bile salts can’t get through

44
Q

what is the con of small porins

A

slow diffusion of molecules

45
Q

what is EnvZ

A

sensing protein

46
Q

what happens in low osmolarity in porin regulation

A 
outside gut = low osmolarity 
Phosphate group transferred EnvZ in inner membrane from regulatory protein OmpR 
ompR phosphate goes towards C
OmpR-P conc always low
will only bind to ompF
OmpC porin not activated
47
Q

what is IHF

A

Small DNA binding protein known to be involved in the regulation of many genes

48
Q

what is IHF made of

A

consists of 2 subunits (α and β)

49
Q

what does IHF do

A 
binds to specific consensus sequence in promoters
5′-TATCAA-3′ and 5′-TTG-3′
pulls DNA round in really tight curve 
IHF can bind and pull it round
change shape to stop promoters bind
50
Q

what happens in high osmolarity in porin regulation

A

inside gut = high osmolarity
Direction of Phosphate transfer is now towards OmpR
[OmpR-P] increased and can now bind to weak promoter binding sites
ompF repressed by DNA bending of promoter induced by IHF binding
ompC porin activated by OmpR-P

51
Q

what are stress responses for

A

required for the survival of individual cells

Cell has to change itself to match the change in the environment

52
Q

how is the role of alternative sigma factors identified

A

identified in controlling sets of genes (regulons) linked to different stress responses

53
Q

what are examples of stresses and different regulatory systems

A 
General stress (RpoS)
Starvation “stringent” response (ppGpp)
Heat shock (DnaK, σ32)
Osmotic shock (K+, compatible solutes, Omps, 2-component response regulators)
54
Q

what regulates which omp porin is made

A

regulated in response to changes in the environmental conditions

Physiology of Microbes (21 decks)

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