Temperature stress and Osmoregulation L9

Question 1

what happens when temperature changes

Answer 1

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

Question 2

what is an arrhenius plot used for

Answer 2

describe the relationship between growth rate and growth temperature

Question 3

effect of temperature on microbes growth

Answer 3

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

Question 4

what occurs at minimum growth rate

Answer 4

membrane gelling

transport processes slow so growth cant occur

Question 5

what occurs between minimum and optimum growth rate

Answer 5

enzymes and reactions occurring at increasingly rapid rate

Question 6

what occurs at optimum growth rate

Answer 6

enzymes and reactions occurring at maximal possible rate

Question 7

what occurs at maximum growth rate

Answer 7

protein denaturation, collapse of cytoplasmic membrane, thermal lysis

Question 8

in frozen water what grows

Answer 8

nothing as microbes need water to grow

Question 9

what is a psychotroph

Answer 9

organism that has an extended growth range

can adapt to extremes of temperature by changing cellular processes

Question 10

what does each single stress response induce

Answer 10

specific set of stress proteins

Question 11

what are stress responses controlled by

Answer 11

alternative sigma factors

Question 12

what happens if stress response genes induced

Answer 12

helps cell repair any damage and adapt to new temperature

Question 13

what happens to the cell after heat shock occurs

Answer 13

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

Question 14

how does cell respond to high temperature stress

Answer 14

inducing synthesis of heat shock proteins (Hsps)

Question 15

what are heat shock proteins function

Answer 15

role in getting proteins to fold correctly

Question 16

how do proteins fold

Answer 16

not all proteins fold spontaneously inside bacterial cells

~30% need assist

Question 17

what do proteins that cant fold need

Answer 17

chaperone

heat shock proteins are chaperones

Question 18

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

Answer 18

20% need DnaJ and DnaK

10-15% also need GroES and GroEL

Question 19

what happens in response to heat shock

Answer 19

needs more heat shock proteins and other new gene products

Question 20

what prevents heat shock gene production

Answer 20

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

Question 21

what happens to the unused sigma 32

Answer 21

targeted for degradation by protease FtsH

Question 22

what happens when heat shock occurs

Answer 22

DnaK now needed in cell to bind to denatured proteins

releases sigma 32 and heat shock proteins induced

Question 23

when is sigma 32 made

Answer 23

sigma 32 always present in cell

Question 24

what happens to DnaK under normal conditions

Answer 24

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

Question 25

what happens when DnaK and DnaJ release sigma 32

Answer 25

can interact with RNAP and switch on heat shock genes

Question 26

how does osmoregulation effect the cell

Answer 26

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

Question 27

what is the most abundant cation in bacteria cytoplasm

Answer 27

potassium

Question 28

when does potassium concentration increase

Answer 28

following hyperosmotic shock

Question 29

what effects potassium concentration

Answer 29

adaptive process so must be reversible

Question 30

what causes potassium influx

Answer 30

response to increasing osmolarity = trk, kdp

Question 31

what causes potassium efflux

Answer 31

response to reducing osmolarity = kdpB, kdpC

Question 32

what operon controls potassium efflux

Answer 32

Encoded by kdpFABC operon

Question 33

what REGULATES potassium efflux

Answer 33

KdpD and KdpE = “2 component response regulator”

Question 34

where is KdpD

Answer 34

inner membrane protein of E. coli

Question 35

what is KdpD

Answer 35

autophosphorylating sensing protein | cytoplasmic regulator protein

Question 36

what happens in Kdp regulation

Answer 36

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

Question 37

when is the kdpFABC operon activated

Answer 37

Switch on in response to potassium depletion outside cell

Question 38

wat happens in kdpFABC operon when high enough potassium

Answer 38

signal goes away | reset system in response to environment

Question 39

what are porins function

Answer 39

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

Question 40

what are the two major porins produced

Answer 40

OmpF | OmpC

Question 41

how do the porins differ

Answer 41

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

Question 42

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

Answer 42

OmpC produced -bile cant get through | Small regulatory proteins involved in controlling this switch

Question 43

what is the pro of small porins

Answer 43

bile salts can't get through

Question 44

what is the con of small porins

Answer 44

slow diffusion of molecules

Question 45

what is EnvZ

Answer 45

sensing protein

Question 46

what happens in low osmolarity in porin regulation

Answer 46

``` 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 ```

Question 47

what is IHF

Answer 47

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

Question 48

what is IHF made of

Answer 48

consists of 2 subunits (α and β)

Question 49

what does IHF do

Answer 49

``` 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 ```

Question 50

what happens in high osmolarity in porin regulation

Answer 50

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

Question 51

what are stress responses for

Answer 51

required for the survival of individual cells | Cell has to change itself to match the change in the environment

Question 52

how is the role of alternative sigma factors identified

Answer 52

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

Question 53

what are examples of stresses and different regulatory systems

Answer 53

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

Question 54

what regulates which omp porin is made

Answer 54

regulated in response to changes in the environmental conditions