Phylogenetic diversity of bacteria associated with the marine sponge Agelas robusta from South China Sea

It is well known that marine sponges harbor large numbers of bacteria, some of which have been proved to be sponge-specific. The diversity of bacteria in marine sponges distributed along the coast of South China Sea has been previously studied but that of bacteria in sponges inhabiting the open sea has been rarely investigated. In this report, the diversity of bacteria associated with the marine sponge Agelas robusta from a remote coral reef in the South China Sea was documented employing 16S rDNA library construction, amplified ribosomal DNA restriction analysis (ARDRA) and phylogenetic analysis. A total of 32 phylotypes were finally categorized in nine phyla including Cyanobacteria, Proteobacteria, Chloroflexi, Firmicutes, Actinobacteria, Acidobacteria, Planctomycetes, Bacteroidetes and Gemmatimonadetes. The dominant phylum was Proteobacteria whereas the dominant genus was Synechococcus in Cyanobacteria. Some spongespecific bacteria were also found in the bacteria population, but the proportion (5 OTUs/32 OTUs) was much lower than other sponges. This study reveals the phylogenetic diversity of bacteria in A. robusta and confirms the presence of some sponge-specific bacteria in the South China Sea. Understanding the diversity of sponge-associated bacteria in China assists to exploit the bacteria resources for biotechnology.