1. Microbial Metabolism Overview of metabolism (you should know about TCA cycle, Embden-Meyerhof pathway- glycolysis, Proton motive force etc.) Overview of nutrition Culture media Energetics Enzyme catalysis Oxidation and reduction Electron carriers Energy conservation

2. Metabolism

3. Energy classes of microbes microbes need three things to grow: –Energy source –Nutrients (C) –Suitable environmental conditions Energy source –Phototroph (light) –Chemotroph (chemicals) Chemoorganotroph (organic chemicals) Chemolithoautotroph (inorganic chemicals)

4. Macronutrients Carbon (CO 2 or organic compounds) Hydrogen (H 2 O or organic compounds) Oxygen (H 2 O or organic compounds) Nitrogen (NH 3, NO 3 -, organic N-compounds) Phosphorus (PO 4 3- ) Sulfur (H 2 S, SO 4 2-, organic compounds) Potassium (K + ) Magnesium (Mg 2+, salts) Sodium (Na + ) Calcium (Ca 2+, salts) Iron (Fe 3+, Fe 2+, or salts)

5. Iron as a nutrient Needed for aerobic metabolism (cytochromes, iron-sulfur proteins) Insoluble under aerobic conditions –Fe(OH) 3, FeOOH –Solubilized by siderophores

6. Siderophore

7. Iron uptake

8. Micronutrients and growth factors Micronutrients: Metals and metalloids –Generally not necessary to add to medium –Deficiencies can arise when medium constituents are very pure Growth factors: organic requirements –Vitamins, amino acids, purines, pyrimidines, acetate

9. Culture media Defined: all chemicals are ostensibly known Complex (undefined): contains substances with unknown chemistries, such as peptones, yeast extract, lake water, soil extract, etc.

10. Energetics Gibbs Free-Energy (G) Reaction has a free-energy change –Negative: exergonic –Positive: endergonic –Zero: equilibrium Standard concentrations—tables of ΔG f °’

11. Redox Reactions Reactions can be written as half-reactions –Oxidation: removal of electrons S → P + e - or H 2 → 2H + + 2e - –Reduction: addition of electrons S + e - → P or O 2 + 4H + + 4e - → 2H 2 O Energetics of redox reactions can be considered as electrical potentials (see electron tower)

12. Calculation of reaction energetics First, must write balanced equation –E.g., 2H 2 + O 2 → 2H 2 O Calculation of ΔG°’ for a reaction –ΔG°’ = ΔG f °’ products - ΔG f °’ reactants –ΔG°’ = 2 x (-237.2 kJ/mol) – (2 x 0 + 0) Calculation of ΔG for a reaction –ΔG = ΔG°’ + RT x ln(k)

13. Electron Tower A redox reaction needs a reducing and oxidizing half-reaction Reactions with stronger tendency to give up electrons are higher (more negative) on the tower To determine which direction the reactions go, see which is “higher” on the electron tower Note the position of important electron carriers (NAD, FAD, cytochrome a) and external electron donors/acceptors (H 2, organic compounds, O 2 )

14. Chemical kinetics and enzyme catalysis

15. Electron carriers: NAD

16. NAD + as co-enzyme

17. NADH as co-enzyme

18. NAD as electron carrier NAD + + ED → ED ox + NADH NADH + EA → EA red + NAD + Overall reaction: –ED +EA → ED ox + EA red

19. High-energy compounds ATP is the energy currency of the cell –High energy released when phosphate is hydrolyzed (ATP, ADP, AMP) Acetyl phosphate Acetyl coenzyme A Phospho-enol pyruvate

20. Modes of E Conservation-ATP Fermentation: in which redox reaction ocurs WITHOUT a terminal electron acceptor (couple oxiation with subsequent reduction of an organic product generated from initial substrate) Respiration: in which O2 or another oxidant serves as an electron acceptor

21. MORE Modes of E generation Anaerobic Respiration Chemolitho(auto)trophy Photo(auto)trophy WHAT DO ALL THESE HAVE IN COMMON?

22. Overview of fermentation