1. Ammonia Oxidizer Enrichment Sarah Douglas Shelbi Russell

2. Ammonia oxidation NH 3 + NH 2 OH NO 2 - AmoABC HAO Bacteria & Archaea Bacteria Archaeal pathway unknown, hydroxylamine may be oxidized by the nitroxyl pathway (Walker et al., 2010)

3. Phylogenetic diversity of ammonia oxidizers Bacteria β-Proteobacteria (Nitrosomonas & Nitrospira) γ-Proteobacteria (Nitrosococcus) Crenarchaeota

4. Sampling Monterey Bay Aquarium activated sand 19°C and 20°C Hopkins sand by aquarium outflow and coast

5. Enrichment procedure Crenarchaeota medium inoculated with 50 mL of 10  M filtered slurry water sample – NH 4 Cl – Cofactors: 7-vitamin, selenite/tungstate, and SL12 trace metal solution – Bicarbonate carbon source – Phosphate buffer Store in the dark Sample every 2 days for 2 weeks

6. Spectrophotometric determination of substrate and product concentration

9. Monterey Bay Aquarium Bradley’s experiment Added 200 uM Ammonia

10. PCR amplification of bacterial and archaeal amoA AOA amoAAOB amoA Monterey Bay Aquarium sand 21° Monterey Bay Aquarium sand 18° Hopkins beach sand Hopkins aquarium sand Positive control

11. Conclusion Bacterial ammonia oxidizers appear to be more prevalent Archaea at competitive disadvantage in high ammonia environments? Lack of correlation between ammonia depletion and nitrite generation: complex ecosystem?