Exploring Nitrogen Fixation in the Susquehanna River

Nitrogen is a key component of all proteins and thus is required for growth and development of all forms of life. The most abundant form of nitrogen is dinitrogen gas (N2) in the atmosphere. However, none of this nitrogen is available for biological use. Dinitrogen must be converted to fixed biological forms—principally as ammonium, NH4, which can be easily incorporated into amino acids for protein synthesis. The production of NH4 from N2 is called nitrogen fixation. Biological nitrogen fixation is restricted to a few members of the Domain Bacteria and Archaea, but within these domains, nitrogen fixation is found in many different phyla. After identifying a nitrogen fixing cyanobacteria (Pseudanabaena strain SR411) in the Susquehanna River, we wondered how widespread nitrogen fixation was in the microbial community of the Susquehanna River. We are taking a two prong approach to determine how prevalent nitrogen fixation is in the microbial community. First, we are isolating and characterizing bacteria that are capable of fixing nitrogen and second, we are using a metagenomics approach to PCR amplify nitrogenase genes from environmental DNA