1. chapter five: microbial metabolism

2. oxidation-reduction redox reaction: coupled reactions
e- removed as part of H atom

3. redox reactions
aerobic respiration
oxygenic photosynthesis

4. nutritional classification: metabolic strategy
aerobic respiration
iron oxidizers
E source to oxidize e-
light/chemical
light energy phototroph
chemical energy chemotroph
carbon source
org./inorganic
photoheterotroph
photoautotroph
chemoheterotroph
chemoautotroph
electron source
organic/inorganic
photoorgano-
heterotroph
photolitho-
chemoorgano-
inorganic
autotroph
oxygen
other inorganic
electron acceptor org./inorganic
fermentation butanediol mixed acid lactic acid alcohol
respiration
chemolitho-
anoxygenic photosynthesis
anaerobic respiration
sulfur oxidizers
oxygenic photosynthesis
e- acceptor oxygen/other
Purple non-
Sulfur bacteria
PSB, GSB, GNSB
Cyanobacteria (plants)
We categorize based on carbon, energy, and electron source
NSP bacteria grow photoheterotrophically using malate or succinate as e-, C and light

5. classifying respiration & photosynthesis

6. complementary metabolism

7. acquiring ATP: substrate level phosphorylation

8. acquiring ATP: oxidative phosphorylation & chemiosmosis

9. heterotrophy: respiration
The ETC process
The ETC overview
Factors affecting the ETC
Switching to fermentation
electron path (oxidation)

10. heterotrophy: respiration & fermentation
C6H12O6
CO2
NAD+
NADH
ETC
ADP + P
lots of ATP
2 H+
reduced e- acceptor
inorganic e-
acceptor
C6H12O6
pyruvate
NAD+
NADH
substrate P
few ATP
lactic acid
ethanol & CO2
mixed acids
butanediol
organic
ferm

11. heterotrophy: respiration & fermentation
inorganic e- acceptor
does NOT mean O2
organic mole.  CO2
fermentation
organic e- acceptor
organic  organic mole.
incomplete H stripping, lower ATP yield
The Kreb’s Cycle
The Kreb’s Cycle in detail

12. metabolism & media

13. Chapter Five Learning Objectives
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?

14. autotrophy: chemosynthesis
chemo-: conversion of chemical E  ATP
iron oxidation
sulfur oxidation
-synthesis: carbon fixation (CO2  organic molecule)
ADP + P
ETC
ATP
NAD NADH
carbon
fixation
2 H+
2Fe2+
2Fe3+
heterotrophy
2 H+
ADP + P
ETC
ATP
NAD NADH
carbon
fixation
H2S
SO42-
heterotrophy

15. chemosynthesis: iron oxidation
Thiobacillus ferrooxidans
chemolithoautotrophy
energy = Fe2+  Fe3+
electron = same
carbon = CO2  CH2O

16. chemosynthesis: sulfur oxidation
Sulfolobus acidocaldarius
chemolithoautotrophy
energy = S2- (sulfide) / S2O32- (thiosulfate)
 SO32- (sulfite)
electron = same
carbon = CO2  CH2O

17. autotrophy: photosynthesis
photo: light E  chemical E
light-dependent (light) reactions
ATP & NAD(P)H “reducing power”
synthesis:
light-independent (dark) reactions
carbon fixation: piling e- onto CO2
H2S/H2O
ADP + P
chlorophyll
ETC
ATP
NAD(P) NAD(P)H
carbon
fixation
oxidized
heterotrophy

18. photosynthetic electron flow & chemiosmosis
cyclic photosynthesis
in the purple sulfur bacteria
non-cyclic photosynthesis
in the cyanobacteria
Comparing Eukaryotic & Prokaryotic photosynthesis

19. microbial CO2 fixation

20. photosynthesis compared
Eukaryotes
Prokaryotes
Algae, Plants
Cyanobacteria
Green Bacteria
Purple Bacteria
electron donor
H2O
H2O or H2S
sulfur compounds
O2 production
oxygenic
oxygenic anoxygenic
anoxygenic
environment
aerobic
aerobic anaerobic
anaerobic
CO2 fixation
Calvin-Benson
Reverse Citric Acid (Reverse Kreb’s)

21. amphibolism & ATP 21

23. 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

24. chapter 5 learning objectives
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?