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Microbial Physiology > Stress > Flashcards

Stress Flashcards

1
Q

What is stress

A

Any deviation from optimal growth conditions that result in a reduced growth rate

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2
Q

How do stress response systems interact together

A

By a complex of global regulatory networks

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3
Q

Types of stress

A

Osmotic
Oxidative
PH
Thermal
Nutrient

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4
Q

Osmotic stress happens when

A

Sudden change in solute conc
Hyper out
Hypo in

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5
Q

Osmoregulation is

A

A process to minimise cell damage

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6
Q

4 ways of osmoregulation

A

Controlling ions efflux and uptake
Accumulation of osmolytes
Osmosensors
Biofilms

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7
Q

Osmolytes func and who

A

Proline, betaine , trehalose
Allow cell to retain water
Protect proteins from denaturation or aggregation
Reduce ROS

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8
Q

Osmosensors are and lead to

A

Proteins that detect osmotic changes
Activation of some genes expression and metabolic adjustments

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9
Q

Biofilm in osmotic stress

A

Physical barrier
Gradient of osmotic conditions
Metabolic interactions
Genetic adaptation like plasmid transfer

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10
Q

Oxidative stress is
Due to

A

Imbalance between ROS and antioxidant mechanism
Disturbance in cells redox state
Aerobic metabolism or exogenously from enivironment

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11
Q

The ROS

A

Superoxide anion o2-

Hydrogen peroxide h2o2
Hydroxyl radical HO’

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12
Q

How ROS transfer to each other

A

O2&raquo_space; O2- by oxidase
O2-&raquo_space; H2O2 by superoxidase dismutase
H2O2&raquo_space; HO’ by peroxidase, most dangerous

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13
Q

2 reactions

A

Haber Weiss&raquo_space; O2- + H2O2 > OH- +OH’ +O2
Fenton&raquo_space; fe2 + H2o2&raquo_space; Fe3 +OH ‘ + OH-

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14
Q

How to regulate oxidative stress

A

Scavenger enzymes, no enzyme for hydroxyl
Redox signals by redox sensitive regulators

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15
Q

The overall reaction

A

Oxygen to superoxide by oxidase
Then to hydrogen peroxide by SODs then to water by catalase or hydroxyl radical by peroxidase

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16
Q

The genes of regulation in oxidative stress

A

SoxRS, respond to superoxide in all
OxyR respond to hydrogen peroxide in negative
PerR respond to hydrogen peroxide in positive
Transcriptional activators, upregulates genes concerned with antioxidative defense and repair mechanisms

17
Q

PH and acid tolerance mechanisms

A

PH homeostasis
Restriction of proton permeation
Consumption of protons
Alteration of cell membrane
Biofilm
Metabolic regulation
Protection and repair of macromolecules

18
Q

What are repair mechanisms in oxidative stress stimulated by redox sensitive regulators

A

Aa biosynthesis
Cell wall synthesis

19
Q

Ph homeostasis
Restriction of proton entry
Proton consumption

A

Proton pumps to pump protons out and import potassium and sodium to counterbalance acidification by antiporters

Less permeable membrane and modulated channel size

Consune excess ex urease combines with H+ to produce ammonia to neutralise the pH in heliobacter pylori

20
Q

Proton pump vs antiporter
Low pH vs High pH

A

Proton pump is unidirectional for protons

Antiporter is bidirectional for a range of ions

Low ph is high conc of protons, high ph is the opposite

21
Q

Altering membrane
Biofilm in pH
Metabolic
macromolecules repair

A

Change in integrity, fluidity and lipid composition to protect from proton influx

Protect and shield by extracellular matrix and interactions

Glycolysis increase by 70 percent

Chaperons protect misfolding and inhibit death signals

22
Q

Why glycolysis increase with low pH

A

ATP production and protons consumption
And fixing the NADH/NAD+ ratio
To compensate the damage

23
Q

What do some bacteria do to stabilise proteins and prevent their denature at low ph

A

Acid shock proteins

24
Q

High temp leads to
Low leads to

A

Denaturation
Disruption of membrane
DNA damage
Metabolic changes

Reduced metabolism and ice formation

25
Q

Mesophiles…leads to heat shock and
…leads to cold shock and code for..

A

40
15
Chaperons

26
Q

The signal controlling heat shock response is..HSP known as…help in..under
Types according to molecular weight

A

Unfolded proteins
Chaperone
Proper folding
Heat stress
HSP70, HSP90, smallHSP

27
Q

HSR phases, induction

A

Induction, in stress but not lethal signal activated transcription factor to increase heat shock genes to overproduce heat shock proteins.

28
Q

HSR adaptation

A

Adaptation, protein structure stabalized and not unfolded, misfolded are not aggregated, refolding of misfolded or denatured, correct folding of new proteins

29
Q

HSR,Steady state

A

Balance between protein synthesis and degradation, sustained as long as stress us present

30
Q

Response to nutrient limitation

A

Starvation
Stringent

31
Q

Starvation aim

A

Adapt till nutrients conditions improve

32
Q

Starvation steps 1

A

Express higher nutrient utilization systems to scavenge nutrients
Degrade glycogen stored for energy, release enzymes to degrade complex molecules and gain nutrients from the environment

33
Q

Starvation steps rest

A

DNA condensation
Ribosome degradation
Endospore
Altering amounts and types of lipid components
Energy saving

34
Q

Why degrade ribosomes
Who can form endospore
energy consuming processes are

A

To gain nutrients
Bacillus and clostridium
DNA replication and cell division

35
Q

Bacteria in starvation can increase…in membrane or adjust its…by…to make the membrane more…and maintain…

A

Unsaturated fatty acids
Thickness
Changing length of fatty acid chains
Fluid
Integrity

36
Q

Stringent response

A

Depletion of amino acids, growth stops them metabolism adjustments to maintain protein synthesis accuracy

37
Q

How stringent response

A

Low DNA replication
Low RNA accumulation esp stable ones r and t
Low biosynthesis of carbs, lipids, peptidoglycans
Shut down of transport of macromolecule precusors

Microbial Physiology (7 decks)

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