1. Nitrogen Cycle Oxidation states Why so important? Next to C cycle..

2. Nitrogen fixation N2 >80% in air Usuable? Anoxic, how? Restricted to prokaryotes e.g.? Enzyme Nitrogenase-2 components, catalyst and e- donor Nif gene and protein synthesis highly regulated Expensive process Assay?

3. Denitrification Opposite of N2-fixation Ecologically important, why? NO3-NO2-NO-N2O-N2 Nitrate respiration, common Nitrite accumulation—carcinogens with amino cmpds NO reductase, NO very labile and doesn’t accumulate N2O reductase inhibited by acetylene

4. Nitrification All prokaryotic, autotrophic (classical) some heterotrophs Ammonia oxidizers –Slow growing, need to couple reactions for E, can oxidize methane, membranes in cells Nitrite oxidizers – a little faster grwing, not much E

5. Anammox Strous M et al. (1999) Missing lithotroph identified as new planctomycete. Nature 400: 446-449. 5 NH 4 + + 3NO 3  4 N 2 + 9H 2 O + 2H +

6. Population Ecology I Cohort, guild, community, ecosystem R or K strategists How do pops change in size? –Exponential growth is like compound interest –Population growth is limited by the environment –Carry capacity –Populations fluctuate about some upper and lower limit –Low population can decline to “extinction” –Metabolic/phenotypic plasticity

7. Population ecology II Intraspecific competition, see cheating example Nature 404:598 Concepts –-coevolution –Niche and co-species Population interactions-2-”spp”

8. Population interactions 2-”spp” systems Type of interactionType AType B neutral00 mutualism++ commensalism+0 competition-- amensalism-0 parasitism+- predation+-