[Prokaryote diversity in the surface sediment of northern South China Sea]

Abstract

Objective: In order to investigate the composition and diversity of prokaryotes in marine surface sediment from site XSCS13 at northern South China Sea.

Method: We extracted environment total DNA directly from the sediment and amplified 16S rRNA genes from the total DNA, thereby constructing 16S rRNA clone libraries of both archaea and bacteria. Then we selected positive clones randomly from the library and identified them by the method of restriction fragment length polymorphism (RFLP). After that, the unique RFLP pattern corresponded sequences were sequenced, BLAST and then constructed into a phylogenetic tree.

Results: Most of the clones were sequences from uncultured microbes. For the Archaea part: the community was mainly comprised of 3 phyla: Crenarchaeota, Thaumarchaeota and Euryarchaeota, among which Crenarchaeota was the dominant class with the percentage of 71%, while Euryarchaeota took the least with only 3 clones. The main group of Crenarchaeota was Marine Group I, taking 61% of all. For the bacteria part, all together 9 phyla were included: 32.6% of Proteobacteria, 3% of Verrucomicrobia, 5.2% of Bacteroidete, 4.44% of Acidobacteria, 6% of Chloroflexi, 3.7% of Firmicute, 5.2% of Planctomycete, 11.1% of Gemmatimonadete and 4.44% of Actinobacteria. Unlike archaea, there's no overwhelming preponderant phylum in bacterium, each phylum was relatively distributed in balanced proportions. Proteobacteria had 3 classes involved: alpha-Proteobacteri, gamma-Proteobacteria and delta-Proteobacteria, and gamma-Proteobacteria stood out with 54.5% of proportion. In addition, over half of all the clones were related to reduction reaction of sulfate and generation of methane.

Conclusion: The research indicated that prokaryote diversity in marine surface sediment from site XSCS13 at northern South China Sea was quite plentiful, and a great mass of abundant microbial resources still remained unknown. Furthermore, the community structure of archaea and bacteria showed that the sampling site may be in a cold spring area with abundant methane.