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Physiology of Microbes > Anaerobic and Aerobic metabolism L14 > Flashcards

Anaerobic and Aerobic metabolism L14 Flashcards

1
Q

what is redox/reduction potential

A

ε is a measure of the tendency of a chemical speciesto acquire electronsand thereby bereduced

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2
Q

what is reduction potential measured in

A

volts (V), or millivolts (mV)

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3
Q

what are the reduction potentials foreach species like

A

each species has its own intrinsic reduction potential

the more positive the potential, the greater the species’ affinity for electrons and tendency to be reduced

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4
Q

what is the terminal electron acceptor in anaerobic respiration

A

a molecule other than oxygen

  • strict anaerobes
  • facultative anaerobes
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5
Q

what does the pathways and energy yields depend on

A

exact electron acceptor

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6
Q

do the more anoxic or oxic bacteria grow fastest

A

oxic grow fastest as get energy

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7
Q

do the more anoxic or oxic bacteria grow slowest

A

very anoxic bacteria don’t generate as much energy from electron transport system so grow very slowly

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8
Q

what is FNR

A

transcription regulator

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9
Q

where is FNR

A

cytoplasm

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10
Q

when is FNR inactivated

A

inactivated by reaction with oxygen

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11
Q

what happens if FNR is inactive

A

cant bind to DNA to affect gene expression

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12
Q

what happens in the absence of oxygen to FNR

A

active form of FNR represses the expression of both the cytochrome d (cydAB ) and cytochrome O (cyoABCDE) operons
Also induces the nar genes required for production of nitrate reductase

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13
Q

what happens in the regulation of gene expression by redox-sensitive Arc and FNR pathways

A
  1. High [O2] ArcB predominates – cyo O made from cyoABCDE
  2. [O2] drops, ArcB-P formed; ArcA-P down regulates cyoABCDE and induces cydAB
  3. [O2] absent FNR activated; cyoABCDE and cydAB repressed other electron acceptors induced
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14
Q

what happens to the TCA cycle during anaerobic respiration

A

becomes branched and generates less NADH

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15
Q

what happens to the TCA functions under anaerobic conditions

A

TCA functions mainly to supply intermediates to biosynthesis

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16
Q

what happens to the left branch reaction under anaerobic conditions in TCA

A 
Left branch reactions reversed and Succinate produced from Oxaloacetate  
Succinate dehydrogenase (Sdh) replaced by Fumarate reductase
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17
Q

what is TCA cycle

A

biosynthetic pathway

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18
Q

why do these changes happen in TCA cycle when anaerobic

A

enzymes need certain environment to work in

cant work in no oxygen

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19
Q

what can happen to an organic compound in aerobic repsiration

A

electron flow form oxygen
this forms ATP from proton motor force

carbon flow leads to biosynthesis

can form carbon dioxide

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20
Q

what can happen to an organic compound in anaerobic respiration

A 
electron flow:
- nitrate ions
- sulfate ions
- organic electron acceptors 
this the forms ATP from proton motor force

carbon flow cause biosynthesis

form carbon dioxide

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21
Q

what is respiration

A

O2 or some other atom serves as terminal electron acceptor

=

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22
Q

what is fermentation

A

oxidation/reduction reactions occur in the absence of a terminal electron acceptor to generate energy

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23
Q

what is involved in substrate level phosphorylation

A

aerotolerant anaerobes
facultative anaerobes under anaerobic conditions and in stationary phase of growth
strict anaerobes

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24
Q

what are the pathways involved in fermentation

A

glycolysis
various reduction pathways
branched TCA cycle in operation

25
Q

what is the net result of fermentation

A

some C atoms converted to CO2; ; the rest excreted

2 ATP molecular from one molecule of glucose

26
Q

what happens in stage 1 of anaerobic respiration

A

preparation

27
Q

what happens in stage 2 of anaerobic respiration

A

oxidation

28
Q

what happens in stage 3 of anaerobic respiration

A

pyruvate goes through various different phosphorylation reactions, can get energy, but also lactate, ethanol, acetyl aldehyde, formate
Which of the pathways predominates depends on exactly what nutrients the bugs are given

29
Q

what is the strickland reaction

A

coupled oxidation and reduction of amino acids to produce organic acids and to release energy
AAs acts as both electron donor and acceptor
Both AAs are converted to carboxylic acids
Donor = lose a carbon
Acceptor = stays same length

30
Q

what uses the strickland reaction, what does it produce

A

Used by amino acid-fermenting microbes to produce ATP by substrate level phosphorylation

31
Q

why is oxygen a ‘killer’

A

At the molecular level oxygen is a killer
Produces free radicals
Causes oxidative damages

32
Q

what is the benefit of oxygen

A

However, oxygen is a hugely efficient terminal electron acceptor
Allows efficient use of organic carbon for faster growth

33
Q

what is oxygen like

A

powerful oxidant and excellent electron acceptor

34
Q

how is superoxide formed

A

O2+ e- –> O2-

35
Q

how is hydrogen peroxide formed

A

O2- + e- + 2H+ –> H2O2

36
Q

how is hydroxyl radical made

A

H2O2 + e- + H+ –> H2O + OH.

37
Q

how is water formed

A

OH. + e- + H+ –> H2O

38
Q

what is the overall oxygen protecting enzyme equation

A

O2 + 4e- + 4H+ –> 2H2O

39
Q

how is oxygen linked to protection

A

Cells have evolved enzymes which break down toxic oxygen products

40
Q

where is peroxidase

A

Present in some aerotolerant bacteria that lack catalase (e.g. lactic acid bacteria)

41
Q

what does peroidase do

A

decomposes H2O2 using electrons from NADH2 to reduce peroxide to H2O

42
Q

where is superoxide reductase

A

in strict anaerobes

43
Q

what does superoxide reductase do

A

reduces superoxide without producing O2

44
Q

what anaerobic jar technique is used for small scale growth studies

A

Brewer Jar or similar container are used
basic principle of all anaerobic jars is the same:
Remove oxygen from chamber: hydrogen and oxygen with catalyst form water

45
Q

what happensin the disposable gas pak

A

H2-CO2 generator used to carry out the reduction of O2 and simultaneously replace it with a CO2 atmosphere

46
Q

what does the disposable gas pak contain

A

sodium borohydride and sodium bicarbonate

small packet of palladium-coated alumina pellets to act as a catalyst in the reduction of O2 to H2O

47
Q

what reaction occurs in the disposable gas pak

A

sodium borohydride and sodium bicarbonate react together when H2O added to produce H2 and CO2

48
Q

how can anaerobic conditions be produced

A

using the evacuation-replacement procedure
the air within the jar is removed by vacuum pump and replaced
with a mixture of 85% N2, 10% H2, and 5% CO2 (pump in gas you want)
Tending to enhance CO2 – as what they require for growth

49
Q

what happens in the branch chain TCA cycle when turns anaerobic

A

need to produce a new enzyme in order to produce succinate, lose a lot of energy as not a continuous cycle – growth is much slower as cant keep using the glucose

50
Q

what is the electron transport chain like when oxygen is available

A

glycolysis producing reducing agents which are then used to pump out H+ ions (later used to generate ATP), cyt O responsible for pumping out one H+ ion. overall 4H+ions out

51
Q

what is the electron transport chain like when oxygen is not available

A

using nitrate reductase, the proteins at the end of the system change, only 3H+ ions pumped out as nitrate reductase cannot pump out H+ ion, thus less ATP

52
Q

what changes in the electron transport chain when no oxygen is available

A

E. coli starts to produce cyt O, when become completely anaerobic this is replaced by nitrate reductase as the electron acceptor
3H+ ions pumped out instead of 4H+
so less ATP

53
Q

what happens in the overall fermentation scheme

A

Organic compound comes in, makes intermediates (act as electron carriers)
NADH brought back into other molecules then forms reduced organic compounds (fermentation product)

54
Q

what happens if different microbes are added to fermentation

A

Put in different microbes, different versions of reduction reactions – produce different molecules at the bottom which causes different flavours e.g. cheese

55
Q

what diagnostic tests are obligate aerobes and most facultative anaerobes positive and negative for

A

+ve superoxide dismutase
+ve catalase
-ve peroxide

56
Q

what diagnostic tests are most aerotolerant anaerobes positive and negative for

A

+ve superoxide dismutase
-ve catalase
+ve peroxide

57
Q

what diagnostic tests are obligate anaerobes positive and negative for

A

-ve superoxide dismutase
-ve catalase
-ve peroxide
Obligate anaerobe has non of these enzymes as they all produce oxygen

58
Q

what is superoxide dismutase like

A

aerobes
facultative anaerobes
some aerotolerant anaerobes
NOT strict anaerobes (generates O2)

59
Q

what is catalase like

A

most strict aerobes
facultative anaerobes
not usual in aerotolerant anaerobes
NOT strict anaerobes (generates O2)

Physiology of Microbes (21 decks)

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