The diversity of alkane-degrading bacterial communities in seagrass ecosystem of the South China Sea

Seagrass meadows are one of the most important marine ecosystems. Alkanes are the common hydrocarbon contaminants that can affect seagrass growth. In this study, a large spatial-scale investigation has been carried out on the alkane-degrading bacterial community structure in the rhizosphere and non-rhizosphere sediments of two seagrass species ( Thalassia hemprichii and Halophila ovalis ). AlkB gene was employed as a biomarker gene to study the alkane-degrading bacterial community structure. The results showed that the alpha diversity of the alkane-degrading bacterial community in T. hemprichii non-rhizosphere sediments was higher than that of its rhizosphere sediments. However, the alpha diversity of the alkane-degrading bacterial community in H. ovalis rhizosphere sediments was higher than that of its non-rhizosphere sediments in the open sea, but the result was contrast in the coast area. In addition, the alpha diversity of alkane-degrading bacterial communities in the coast area was higher than that of far away from the coast in the T. hemprichii rhizosphere and non-rhizosphere sediments. The phylogenetic analysis result revealed that the alkB sequences from the seagrass ecosystem were mainly affiliated with the class Alphaproteobacteria, and had the two novel lineages. Genus Agrobacterium was the most predominant alkane-degrading bacteria. These results contributed to disclose the geographical distribution pattern of alkane-degrading bacteria in the seagrass ecosystem of the South China Sea.