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Physiology of Microbes > Bacterial Aerobic Respiration L13 > Flashcards

Bacterial Aerobic Respiration L13 Flashcards

1
Q

what is the terminal electron acceptor

A

in aerobic respiration oxygen is used as terminal electron acceptor in electron transport chain

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2
Q

what are the pathways in aerobic respiration

A

glycolysis
Krebs cycle/citric acid cycle (CAC)/tricarboxylic acid cycle(TCA)
oxidative phosphorylation via electron transport chain

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3
Q

what is the net result of aerobic respiration

A

all C atoms in glucose are converted to carbon dioxide

38 ATP molecules from one molecule of glucose

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4
Q

where does glycolysis and TCA cycle occur in bacteria

A

in bacteria glycolysis and the TCA cycle occur in the cytoplasm

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5
Q

what happens to the electrons after glycolysis and TCA cycle

A

electrons are picked up from intermediates of glycolysis and TCA cycle by NAD /FAD

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6
Q

what produces NADH

A

conversion of pyruvic acid to acetyl CoA

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7
Q

what does NADH and FADH2 do

A

NADH or FADH2 take the electrons to the electron transport chain

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8
Q

what creates the most ATP

A

Most ATP is generated by the chemi-osmotic potential generated as part of electron transport = oxidative phosphorylation

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9
Q

what reactions in glycolysis use ATP

A

glucose in cell and prepared we start to consume ATP – preparatory reactions use ATP

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10
Q

what happens in stage 2 glycolysis

A

+2 ATP
+1 NADH
-1 Pi

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11
Q

what is the structure of glucose at the start of the reaction

A

glucose –> glucose-6-phosphate

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12
Q

what is formed at the end of glycolysis

A

pyruvate 3 carbon atoms

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13
Q

what is produced in the TCA cycle

A

3 carbon dioxide
4 NADH
FADH
GTP

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14
Q

what happens in the TCA cycle

A

pyruvate enters lose COA = acetyl Coa
Lose c if lose a CO2
Join cycle with a4 c
Lose two more carbon round cycle

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15
Q

how does the electron transport system allow energy conservation

A

production of the proton motive force which is used to synthesise ATP

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16
Q

what is oxidative phosphorylation

A

electrons ——————->O2
ADP–>ATP
electron flow - proton motive force

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17
Q

what is a classic experiment to show bacteria can grow under a range of different atmospheric conditions

A

Bacteria are inoculated at low cell density (not visible) into soft agar
Poured into test tubes and incubated to allow growth
agar becomes opaque = growth
Cells evenly distributed in the tube wont move around as embedded in agar

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18
Q

what happens if oxygen is the terminal electron acceptor - patterns of growth in test tube

A

growth at top where oxygen is

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19
Q

what happens if bacteria grows all through the tube

A

doesn’t require oxygen for growth

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20
Q

what do patterns reveal - growth of bacteria in test tubes

A

ability of bacteria to adapt to different levels of oxygen present in their environment

21
Q

how does the bacterial electron transport chain differ to mitochondria

A

Bacterial electron transport chains are usually shorter than those in mitochondria

22
Q

how do the bacterial electron transport chains vary

A

contain different cytochromes

also contain branches allowing alternative routes of electron flow

23
Q

what are the cytochromes

A

CytO

CytD

24
Q

what is CytO

A

better at pumping out hydrogen levels, but limited as not as good at finding oxygen
high aeration, fast growth

25
Q

what is CytD

A

better at scavenging oxygen when low

low aeration, stationary phase growth

26
Q

what is NADH

A

electron donor

27
Q

what is ubiquinone

A

(Q) connects NADH dehydrogenase to branches I and II

28
Q

what happens in electron transport

A

Electrons pumped out – energise, membrane
Electron go from cytochrome B to O
On other side B B D
Different options of which cytochromes will form complexes
Change depending on the conditions

29
Q

why does the system change between CtyO and CytD

A 
System I (Cyt D) is better at scavenging oxygen when concentrations are low but is less efficient at pumping out H+ ions
System II (Cyt O) is better at pumping out H+ ions but requires higher oxygen concentrations to function
Different systems used to optimise energy production depending on the external environment
30
Q

what is ArcB

A

transcription regulator

31
Q

what does the transcription regulator do

A

senses the levels of O2 and switches from low affinity to high affinity cytochromes
will pickup phosphate and autophosphorylate in response to lower [O2 ]
Transfers phosphate to cytoplasmic ArcA which can regulate gene expression

32
Q

cytochrome O

A

cyoABCDE

33
Q

cytochrome D

A

cydAB

34
Q

where is ArcB

A

in the membrane

35
Q

what happens in regulation of gene expression by redox-sensitive Arc

A
  1. High [O2] ArcB predominates – cyo O made from cyoABCDE
  2. [O2] drops, ArcB-P formed;
  3. ArcA-P down regulates cyoABCDE
  4. ArcA-P induces cydAB
36
Q

what is the response of further growth patterns

A

responses are bacteria making different cytochromes

37
Q

what is a way we can classify bacteria according to growth pattern

A

bacteria can grow under different atmospheric conditions

38
Q

what is a strict aerobe

A

cant grow without oxygen

growth at top of test tube only

39
Q

example of a strict aerobe

A

pseudomonas spp.

40
Q

what is a facultative anaerobe

A

grows fastest with oxygen but can grow without

growth most at top of test tube and spreads down

41
Q

what is an example of a facultative anaerobe

A

Enterobacteriaceae (e.g. Escherichia coli);

has to live in the environment and in the GI tract

42
Q

what is a microaerophile

A

requires lower oxygen than atmospheric growth

growth only under the ‘agar’ at top of the test tube

43
Q

example of a microaerophile

A

campylobacter

Intestinal pathogen capable of surviving in the environment

44
Q

what is aerotolerant anaerobe

A

grows best anaerobically but tolerates oxygen evolved before oxygen around
growth throughout test tube

45
Q

examples of aerotolerant anaerobe

A

Lactobacillus & Streptococcus

used in fermentations (cheese & yoghurt)

46
Q

what is a strict anaerobe

A

requires O2 to be absent

growth only at the bottom of the test tube

47
Q

examples of strict anaerobe

A

Clostridium spp. in soil
C. tetani in deep wounds
C. perfringens causing GI infections
Methanogens in GI tract

48
Q

what is a canophile

A

grows best with raised carbon dioxide levels

microaerophiles and aerotolerant anaerobes

Physiology of Microbes (21 decks)

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