1. Ocean-atmosphere through time Lyons, 2008, Science 321, p. 923-924.

2. From Reinhard et al., 2009, Science Vol.326, p. 713

3. Earth’s Oceans @ 2.5 Ga From Reinhard et al., 2009, Science Vol.326, p. 713

4. Geomicrobiology

5. Classification of life forms: –Eukaryotic = Plants, animals, fungus, algae, and even protozoa –Prokaryotic = archaea and bacteria Living cells can: –Self-feed –Replicate (grow) –Differentiate (change in form/function) –Communicate –Evolve Can purely chemical systems do these things? All of these things? Why do we care to go through this ?

6. Tree of life

7. Diversity There are likely millions of different microbial species Scientists have identified and characterized ~10,000 of these Typical soils contain hundreds- thousands of different species Very extreme environments contain as little as a few different microbes

8. Characterizing microbes Morphological and functional – what they look like and what they eat/breathe –Based primarily on culturing – grow microbes on specific media – trying to get ‘pure’ culture Genetic – Determine sequence of the DNA or RNA – only need a part of this for good identification Probes – Based on genetic info, design molecule to stick to the DNA/RNA and be visible in a microscope

9. Environmental limits on life Liquid H 2 O – life as we know it requires liquid water Redox gradient – conditions which limit this? Range of conditions for prokaryotes much more than that of eukaryotes – inactive stasis Spores can take a lot of abuse and last very long times Tougher living = less diversity Closer to the limits of life – Fewer microbes able to function

10. Profiles and microbial habitats O2O2 H2SH2S Concentration depth Fe 2+ H2SH2S O2O2 Org. C 1 2 3 4 Life requires redox disequilibrium!!

11. Phototrophic mats - PSB Purple sulfur bacteria mats –Respond to light level changes in minutes  position in sediment and water column can vary significantly!

12. Cell Metabolism Based on redox reactions –Substrate (food) – electron is lost from this (which is oxidized by this process) –that electron goes through enzymes to harness the energy for the production of ATP –Electron eventually ends up going to another molecule (which is reduced by this)

13. The Redox ladder H2OH2O H2H2 O2O2 H2OH2O NO 3 - N2N2 MnO 2 Mn 2+ Fe(OH) 3 Fe 2+ SO 4 2- H2SH2S CO 2 CH 4 Oxic Post - oxic Sulfidic Methanic Aerobes Dinitrofiers Maganese reducers Sulfate reducers Methanogens Iron reducers The redox-couples are shown on each stair-step, where the most energy is gained at the top step and the least at the bottom step. (Gibb’s free energy becomes more positive going down the steps)

14. Redox gradients and life Microbes harness the energy present from DISEQUILIBRIUM Manipulate flow of electrons O2/H2O C 2 HO

15. Nutrition value Eukaryotes (like us) eat organics and breathe oxygen Prokaryotes can use other food sources and acceptors

16. Microbes, e- flow Catabolism – breakdown of any compound for energy Anabolism – consumption of that energy for biosynthesis Transfer of e- facilitated by e- carriers, some bound to the membrane, some freely diffusible

17. Exergonic/Endergonic Thermodynamics tells us direction and energy available from coupling of 2 half- reactions Energy available = -  G 0 = exergonic Organisms use this energy for life!!

18. Calculating Potential Energy Thermodynamic Modeling ∆Gr = ∆Gr ۫ + RTlnQ ∆Gr ۫ = Σ vi,r * ∆Gi ۫ (products) - Σ vi,r * ∆Gi ۫ (reactants) Q = π a i vi,r (products)- π a i vi,r (reactants) R = 8.3141 J/mol*K (Gas Constant) T = 85 C

19. Example 2 S 5 -2 + 2 H + = 2 HS - + S 8 ∆G r ۫ = ((HS - ) 2 + (S)) -(( S 5 -2 ) 2 + (H + ) 2 ) ∆G r ۫ = -101.64 kJ/mol Species∆G i Formation S-2.04 S 5 -2 58.13 H+H+ 0 HS - 8.33 Calculating Potential Energy Thermodynamic Modeling Q = ((HS - ) 2 * S)/(( S 5 -2 ) 2 * (H + ) 2 ) Q = 2.46E -9 kJ/mol Specieslog activityactivity S 5 -2 -8.711.95E-09 HS - -9.4793.32E-10 H+H+ -1.7710.016943 S01 ∆G r = ∆Gr ۫ + RTlnQ ∆G r = -101.64 + 8.3141*358.15*ln(2.46E -9 ) ∆G r = -160.17 kJ/mol for 4 electrons ∆G r /e - = -40 kJ/mol

20. NAD + /NADH and NADP + /NADPH Oxidation-reduction reactions use NAD + or FADH (nicotinamide adenine dinucleotide, flavin adenine dinucleotide). When a metabolite is oxidized, NAD + accepts two electrons plus a hydrogen ion (H + ) and NADH results. NADH then carries energy to cell for other uses

21. transport of electrons coupled to pumping protons glucose e- CH 2 O  CO2 + 4 e- + H+ 0.5 O 2 + 4e - + 4H +  H 2 O

22. Proton Motive Force (PMF) Enzymatic reactions pump H + outside the cell, there are a number of membrane- bound enzymes which transfer e - s and pump H + out of the cell Develop a strong gradient of H + across the membrane (remember this is 8 nm thick) This gradient is CRITICAL to cell function because of how ATP is generated…

23. HOW IS THE PMF USED TO SYNTHESIZE ATP? catalyzed by ATP synthase BOM – Figure 5.21

24. Other nutrients needed for life Besides chemicals for metabolic energy, microbes need other things for growth. –Carbon –Oxygen –Sulfur –Phosphorus –Nitrogen –Iron –Trace metals (including Mo, Cu, Ni, Cd, etc.) What limits growth??

25. Nutrients Lakes are particularly sensitive to the amount of nutrients in it: –Oligotrophic – low nutrients, low photosynthetic activity, low organics  clear, clean… –Eutrophic – high nutrients, high photosynthetic activity, high organics  mucky, plankton / cyanobacterial population high Plankton growth: 106 CO 2 + 16 NO 3 - + HPO 4 2- + 122 H 2 O + 18 H + + trace elements + light  C 106 H 263 O 110 N 16 P 1 + 138 O 2 (organic material composing plankton) –This C:N:P ratio (106:16:1) is the Redfield Ratio –What nutrients are we concerned with in Lake Champlain?

26. Nutrient excess can result in ‘blooms’

27. Lake Champlain –Phosphorus limited? –Algal blooms –What controls P??

28. Nutrient cycling linked to SRB-IRB- MRB activity Blue Green Algae blooms FeOOH PO 4 3- Org C + SO 4 2- H2SH2S FeS 2 PO 4 3- Sulfate Reducers