New connectivity between carbon and nitrogen cycles-nitrite/nitrate coupled methane oxidation

Recent but very limited research shows that the nitrogen cycle depicted by ecologists and engineers is not complete and that some novel nitrogen transformation pathways are missing. One such example is the denitrification of nitrate/nitrite directly using methane as the carbon source, hereafter referred as anoxic methane oxidation (AMO) with nitrite/nitrate as electron acceptor. This important biochemical reaction, which has both eco logical as well as engineering significance, provides a novel connectivity between nitrogen and carbon cycles. Furthermore, this new pathways enables wastewater practitioners to consider some important nitrogen transformation pathways in wastewater treatment and, enables ecologists to consider yet overlooked anoxic methane oxidation in many ecosystem. This presentation will first include an overview of the topic, followed by results on current research in this topic in our lab demonstrating the kinetics of denitrification, methane oxidation and revealing the identity of novel organisms participating in this important process. Our data suggests that nitrate and nitrite and methane consumption rates were 0.525mg/L/day, 0.29mg/L/day and 4.33.mg/L/day, respectively in an enrichment culture which was seeded from river sediments. Whole community metagenomi analysis on original sediments and reactor biomass clearly shows that specific genes participating in nitrogen transformations are enriched in the reactor. Cloning and sequencing based on 16S rDNA shows that bacteria belonging to NC phylum are enriched but they are different from those recently published in the limited literature.