Diversity of nifH gene sequences in the sediments of South China Sea

In order to contribute to knowledge about structure of marine diazotrophic communities in the sediments of South China Sea, the molecular diversity of the nifH gene, which encodes the Fe protein of the nitrogenase complex, was assessed by polymerase chain reaction (PCR) amplification using PolF/R primers, followed by cloning and sequencing. Sequences of nifH genes were amplified from environmental deoxyribonucleic acid (DNA) samples collected during three stations including shallow sea (75 m, station L10), shelf (450 m, station L2) and deep sea (1000 m, station L21), and covering an area between 17 to 19 degrees N and 111 to 119 degrees E. Samples from shallow sea contained beta-, and delta-proteobacteria; the shelf contained alpha-, beta-, delta- proteobacteria; the deep sea contained alpha-, delta-,. y-proteobacteria, firmicutes, and green nonsulfur (GNS) bacterium. These results suggested that diazotroph was significant component potentially contributing to nitrogen fixation in South China Sea.