chapter five:
microbial metabolism
oxidation-reduction
redox reaction: coupled reactions
e- removed as part of H
atom
redox reactions
aerobic respiration
oxygenic photosynthesis
nutritional classification: metabolic strategy
E source to oxidize elight/chemical
light energy
phototroph
chemical energy
chemotroph
carbon source
org./inorganic
carbon source
org./inorganic
photoheterotroph
photoautotroph
chemoheterotroph
electron source
organic/inorganic
photoorganoheterotroph
Purple nonSulfur bacteria
electron source
inorganic
electron source
org./inorganic
photolithoheterotroph
chemoorganoheterotroph
photolithoautotroph
chemolithoheterotroph
chemoautotroph
electron source
org./inorganic
chemoorganoautotroph
electron acceptor
org./inorganic
chemolithoautotroph
oxygen
other inorganic
oxygenic
photosynthesis
anoxygenic
photosynthesis
Cyanobacteria
(plants)
PSB, GSB, GNSB
fermentation
butanediol
mixed acid
lactic acid
alcohol
respiration
e- acceptor
oxygen/other
aerobic
respiration
anaerobic
respiration
sulfur oxidizers
iron oxidizers
classifying respiration & photosynthesis
complementary metabolism
acquiring ATP: substrate level phosphorylation
acquiring ATP: oxidative phosphorylation &
chemiosmosis
heterotrophy: respiration
The ETC process
The ETC overview
Factors affecting the ETC
Switching to fermentation
electron path
(oxidation)
heterotrophy: respiration & fermentation
inorganic eacceptor
+
C6H12O6
NAD
CO2
NADH
reduced
e- acceptor
ETC
ADP + P
lots of ATP
2 H+
C6H12O6
NAD+
organic
pyruvate
lactic acid
ethanol & CO2
mixed acids
butanediol
ferm
pyruvate
NADH substrate P
few ATP
heterotrophy: respiration & fermentation
respiration
• inorganic e- acceptor
• does NOT mean O2
• organic mole.  CO2
fermentation
• organic e- acceptor
• organic  organic mole.
• incomplete H stripping,
The Kreb’s Cycle
The Kreb’s Cycle in detail
lower ATP yield
metabolism & media
Chapter Five Learning Objectives
1.
2.
3.
4.
5.
6.
7.
Discuss redox reactions in biological systems.
Identify the redox partners in aerobic and anaerobic respiration and oxygenic and anoxygenic photosynthesis.
Correctly identify the carbon, energy and electron source for an organism when given its nutritional classification (e.g.,
chemoorganoheterotroph).
How is ATP generated in both substrate level and oxidative phosphorylation?
Why is it so important that the electron transport chain is housed in a lipid bilayer membrane? Why is a terminal electron
acceptor so important?
What happens in a microorganism if the terminal electron acceptor of the ETC is not available? What molecules build up?
What is done with these molecules?
Discuss the major differences between respiration and fermentation. What are the four basic kinds of fermentation?
autotrophy: chemosynthesis
• chemo-: conversion of chemical E  ATP
• iron oxidation
NAD+
NADH
2Fe2+
2 H+
ETC
carbon
fixation
2Fe3+
ADP + P
• sulfur oxidation
H2S
SO42-
ATP
heterotrophy
NAD+
NADH
+
2H
ETC
ADP + P
ATP
carbon
fixation
heterotrophy
• -synthesis: carbon fixation (CO2  organic molecule)
chemosynthesis: iron oxidation
Thiobacillus ferrooxidans
chemolithoautotrophy
• energy = Fe2+  Fe3+
• electron = same
• carbon = CO2  CH2O
chemosynthesis: sulfur oxidation
Sulfolobus acidocaldarius
chemolithoautotrophy
• energy = S2- (sulfide) / S2O32- (thiosulfate)
 SO32- (sulfite)
• electron = same
• carbon = CO2  CH2O
autotrophy: photosynthesis
• photo: light E  chemical E
– light-dependent (light) reactions
– ATP & NAD(P)H “reducing power”
chlorophyll
NAD(P)
NAD(P)H
ETC
H2S/H2O
oxidized
chlorophyll
ADP + P
• synthesis:
– light-independent (dark) reactions
– carbon fixation: piling e- onto CO2
carbon
fixation
ATP
heterotrophy
photosynthetic electron flow & chemiosmosis
cyclic photosynthesis
in the purple sulfur bacteria
non-cyclic photosynthesis
in the cyanobacteria
Comparing Eukaryotic & Prokaryotic photosynthesis
microbial CO2 fixation
photosynthesis compared
Eukaryotes
Algae, Plants
Prokaryotes
Cyanobacteria
Green Bacteria
Purple Bacteria
electron donor
H2 O
H2O or H2S
sulfur compounds
sulfur compounds
O2 production
oxygenic
oxygenic
anoxygenic
anoxygenic
anoxygenic
environment
aerobic
aerobic
anaerobic
anaerobic
anaerobic
CO2 fixation
Calvin-Benson
Calvin-Benson
Reverse Citric Acid
(Reverse Kreb’s)
Calvin-Benson
amphibolism & ATP
metabolic diversity: the non-sulfur purple bacteria
• chemoheterotrophic growth
– aerobic respiration
– fermentation
• photoautotrophic growth
– anaerobic, anoxygenic photosynthesis H2 for e- & CO2 for C
• photoheterotrophic growth
– anaerobic, anoxygenic photosynthesis C6H6O4 (succinate) for
both
chapter 5 learning objectives
1.
2.
3.
4.
5.
How is ATP generated in chemosynthesis, photosynthesis and respiration? How is the process different for each and
how is it the same?
Discuss the redox partners of sulfur and iron oxidizing bacteria.
How do non-cyclic and cyclic photosynthesis differ? How does each produce ATP and NADPH/NADH? What is each used
for?
How is carbon fixed during chemosynthesis and photosynthesis? How is the process similar and how is it different?
How do amphibolism, catabolism and anabolism relate to growth and repair in cells?