Diversity of the aerobic anoxygenic phototrophy gene pufM in Arctic and Antarctic coastal seawaters

Abstract

Aerobic anoxygenic phototrophic (AAP) bacteria serve important functions in marine carbon and energy cycling because of their capability to utilize dissolved organic substrates and harvest light energy. AAP bacteria are widely distributed in marine environments, and their diversity has been examined in marine habitats. However, information about AAP bacteria at high latitudes remains insufficient to date. Therefore, this study determined the summer AAP bacterial diversity in Arctic Kongsfjorden and in the Antarctic coastal seawater of King George Island on the basis of pufM, a gene that encodes a pigment-binding protein subunit of the reaction center complex. Four pufM clone libraries were constructed, and 674 positive clones were obtained from four investigated stations (two in Kongsfjorden and two in the Antarctic Maxwell Bay). Arctic clones were clustered within the Alphaproteobacteria, whereas Antarctic clones were classified into the Alphaproteobacteria and Betaproteobacteria classes. Rhodobacteraceae-like pufM genes dominated in all samples. In addition, sequences closely related to pufM encoded on a plasmid in Sulfitobacter guttiformis were predominant in both Arctic and Antarctic samples. This result indicates the transpolar or even global distribution of pufM genes in marine environments. Meanwhile, differences between the Arctic and Antarctic sequences may prove polar endemism. These results indicate the important role of Rhodobacteraceae as AAP bacteria in bipolar coastal waters.