Virginia Institute of Marine Science
FRONTIERS IN MICROBIOLOGY
Dissimilatory nitrate reduction to ammonium (DNRA) and denitrification are two nitrate respiration pathways in the microbial nitrogen cycle. Diversity and abundance of denitrifying bacteria have been extensively examined in various ecosystems. However, studies on DNRA bacterial diversity are limited, and the linkage between the structure and activity of DNRA communities has yet to be discovered. We examined the composition, diversity, abundance, and activities of DNRA communities at five sites along a salinity gradient in the New River Estuary, North Carolina, USA, a shallow temporal/lagoonal estuarine system. Sediment slurry incubation experiments with N-15-nitrate were conducted to measure potential DNRA rates, while the abundance of DNRA communities was calculated using quantitative PCR of nrfA genes encoding cytochrome C nitrite reductase, commonly found in DNRA bacteria. A pyrosequencing method targeting nrfA genes was developed using an Ion Torrent sequencer to examine the diversity and composition of DNRA communities within the estuarine sediment community. We found higher levels of nrfA gene abundance and DNRA activities in sediments with higher percent organic content. Pyrosequencing analysis of nrfA genes revealed spatial variation of DNRA communities along the salinity gradient of the New River Estuary. Percent abundance of dominant populations was found to have significant influence on overall activities of DNRA communities. Abundance of dominant DNRA bacteria and organic carbon availability are important regulators of DNRA activities in the eutrophic New River Estuary.
DISSIMILATORY NITRATE REDUCTION; C NITRITE REDUCTASE; NITROGEN-CYCLE; FRINGING MARSH; AMMONIUM DNRA; RIVER-ESTUARY; DENITRIFICATION; SEDIMENT; AMMONIFICATION; DIVERSITY
This study was supported through grants provided by the US National Science Foundation (DEB1020944, EAR1024662, and OCE0851435). We acknowledge Ashley Smyth and Ann Arfken for providing comments and feedback on this manuscript. This paper is Contribution No. 3393 of the Virginia Institute of Marine Science, College of William & Mary.
Song, Bongkeun; Lisa, Jessica A.; and Tobias, Craig R., Linking DNRA community structure and activity in a shallow lagoonal estuarine system (2014). FRONTIERS IN MICROBIOLOGY, 5.