PRESENCE AND ABUNDANCE OF SAR11-NAR GENES IN OXYGEN MINIMUM ZONES

Abstract

Based on future climate projections, tropical Oxygen Minimum Zones (OMZs) are set to grow. Within OMZs, organisms need to be adapted to low oxygen environments, yet SAR11, one of the most abundant organisms in every layer of the ocean, including OMZs, is typically characterized as an aerobic heterotroph. Two different narG genes, used to represent the canonical pathway of nitrate reduction, were recently identified in SAR11 from the Eastern Tropical North Pacific OMZ (termed OP1-like and gamma-like), yet these narG have yet to be found in any other OMZ. The purpose of this project is to identify the distribution of the two narG genes globally, and understand factors that could lead to shift in populations of SAR11 with the genes. Through analysis of 23 metagenomes, the relative abundance of the genes was determined for locations in the ETNP, Eastern Tropical South Pacific, and Arabian Sea. The relative abundances showed similar distributions in every basin, with a peak around 200-300m. Further qPCR experiments on OP1-like narG in the ETNP showed similar results based on the abundance. Both genes showed relatively high correlation with nitrate concentrations, and weak correlation with oxygen. These results show that the two genes are globally distributed, and highly present in OMZs, clarifying the structure and similarity of microbial communities across OMZ basins.