1. Chapter 5 Metabolism

4. 3 Questions About Microbial Metabolism
How do microbes metabolize glucose?
How do microbes generate ATP?
How do microbes get around abnormal conditions?

5. 3 Ways to Metabolize Glucose
Glycolysis
Pentose Phosphate
Entner-Doudoroff Pathway.

6. Glycolysis (Embden Meyerhof)
Major route to pyruvate (sweet loosening)
Has 6 C stage and 3 C stage
net 2 ATP’s (substrate level phos.)
Pathway p. 138 (transparency).

9. Functions of Glycolysis
Major route of hexoses to pyruvate
Provides 6/12 critical intermediates
Generates energy.

10. Limitations of Glycolysis
Still need 5 carbon sugars (DNA, RNA)
Erythrose - 4 Phosphate needed for aromatic amino acids
Need NADPH.

11. Don’t Worry Be Happy! Solution for Most Microbes is
Pentose Phosphate Pathway

12. Pentose Phosphate Pathway - Hexose Monophosphate Shunt
Can occur aerobically or anaerobically
Two enzymes critical
transketolase: transfers 2-carbon molecules
transaldolase: transfers 3-carbon molecules
Pathway p. 140 (transparency).

15. Functions of Pentose Phosphate
Generates NADPH
Generates 4 and 5-carbon sugars
Ribose 5 Phosphate
Intermediates used to make ATP.

16. Entner - Doudoroff Pathway
Alternative to Pentose P. & Glycolysis
Provides 5/12 critical metabolites
Pathway p. 174 (transparency)
Found in Pseudomonas, Rhizobium, Azotobacter, Enterococcus.

17. Glycolysis vs. Entner Doudoroff
Both convert glucose to two molecules of pyruvate
In ED, one pyruvate from top half, other from G3P
In glycolysis, both pyruvates arise from G3P.
ATP from ED 1/2 of Glycolysis.

19. Tricarboxylic Acid Cycle (Krebs)
Provides remaining intermediates
Generates energy NADH & FADH2
Found in all aerobes & most anaerobes
Amphibolic
Pathway p. 183 (transparency).

21. ATP Generation Substrate Level Phosphorylation Photophosphorylation
Oxidative Phosphorylation.

22. Electron Transport
Electrons progressively transferred from donors to acceptors
Passed from NADH and FADH2 to electron carriers in membrane
Ends at terminal electron acceptors -- oxygen.

23. Electron Transport High potential difference = energy production
ET produces proton gradients --- makes ATP.

24. H2 e-
2H+
Electron Transport

25. H2 e-
2H+
Electron Transport

26. H2 e-
2H+
Electron Transport

27. H2
ATP
2H+ e-
Electron Transport

28. H2
2H+ e-
Electron Transport

29. H2
2H+ e-
Electron Transport

30. H2
2H+
ATP e- O2
Electron Transport
H2O

31. Oxidative Phosphorylation
Production of ATP at expense of proton motive force from ET.

33. Fermentation Without O2, NADH not oxidized by ET
NADH (glycolysis) must be oxidized
Some use pyruvate as terminal electron acceptor
Organic molecules are terminal electron acceptors.

35. Fermentation Types

37. Anaerobic Respiration
Terminal electron acceptors inorganic - nitrate, sulfate, carbon dioxide
Not as efficient at ATP synthesis as aerobic.

38. Anaerobic Respiration Types
Dissimilatory Nitrate Reduction: nitrate reduced to nitrite
Denitrification: nitrate reduced to nitrogen gas (Pseudomonas, Bacillus)
Sulfate Reduction: sulfate reduced to sulfide (Desulfovibrio)
Methanogenesis: carbon dioxide converted to methane.

39. Microbes for Sale!