Abundant presence of the γ-like ProteobacterialpufMgene in oxic seawater

Known anoxygenic photosynthetic bacteria (APB) affiliated to Gammaproteobacteria usually use anaerobic metabolism and are restricted to oxygen-free habitats. Here, we report abundant (average of 34.5%) presence of diverse APB related to gamma-like Proteobacteria in oxic oceanic surface water as indicated by the pufM gene, that encodes the M subunit of the light reaction centre complex. Thus, our sequences were most likely derived from aerobic anoxygenic phototrophs (AAnP). Two genetically distinct genotypes were revealed: one was from the oligotrophic North Pacific Ocean Gyre and the other, was from the trophic East China Sea and Bering Sea. The discovery of abundant presence of novel gamma-like Proteobacterial pufM gene in the oxic seawater extends the functional ecotypes of AAnP.