Genetic Distribution Of Aerobic Anoxygenic Photosynthetic Bacteria Based On PufM Gene In Representative Marine Environments

Aerobic Anoxygenic Phototrophic Bacteria (AAPB) are a newly recognized functional group of microorganisms. They are obligate aerobe and the bacteriochlorophyll a (BChla) based photosynthesis is a supplement to their normal diet of dissolved organic carbon (DOC). Their unique physiological function is of potential great ecological importance in carbon cycling in the ocean. Known cultivated representatives of this functional group belong to only a few restricted groups within theα-class andβ-class of Proteobacteria. Culture-independent environmental and genomic analyses of the photosynthetic gene content and operon organization identified the existence ofβ-like Proteobacterial AAPB. In order to clarify the significance and diversity of AAPB along ecological gradients based on analysis of pufM gene encoding the M subunit of anoxygenic photosynthetic reaction centers, we sampled in Xiamen Bay, Yangtse Estuarine, East China Sea, South China Sea, Eastern North Pacific Ocean, North Pacific Gyre and Bering Sea, covering temperate, subtropical, arctic zones and oceanic, continental shelf, and estuarine waters.We detected that Roseobacter-like AAPB distributed widely in marine environments and occupied an important portion of AAPB. The abundance of AAPB belonging to Erythrobacter genus is not high in our investigated seawater. Planktonic bacterial assemblages contain multiple, distantly related, photosynthetically active bacterial groups, including some unrelated to known and cultivated types. And we newly discovered diverseγProteobacterial-like AAPB, extending the AAPB family from the knownα-,β- toγ-Proteobacterial class. Trophic level is an important affecting factor of AAPB's genetic distribution. The higher is the trophic level, the less is the OTU of pufM gene. In the investigation of a vertical water column in shelf water (ECS-P6 station), we found that AAPB diversity showed a light-dependent distribution pattern. Thus, AAPB tend to develop niche-driven ecotypes according to marine environmental properties such as trophic level and light transparence.