Bacterial community diversity of the deep-sea octocoral<i>Paramuricea placomus</i>

Abstract

Compared to tropical corals, much less is known about deep-sea coral biology and ecology. Although the microbial communities of some deep-sea corals have been described, this is the first study to characterize the bacterial community associated with the deep-sea octocoral, <i>Paramuricea placomus</i>. Samples from five colonies of <i>P. placomus</i> were collected from Baltimore Canyon (379-382 m depth) in the Atlantic Ocean off the east coast of the United States of America. DNA was extracted from the coral samples and 16S rRNA gene amplicons were pyrosequenced using V4-V5 primers. Three samples sequenced deeply (>4,000 sequences each) and were further analyzed. The dominant microbial phylum was Proteobacteria, but other major phyla included Firmicutes and Planctomycetes. A conserved community of bacterial taxa held in common across the three <i>P. placomus</i> colonies was identified, comprising 68-90% of the total bacterial community depending on the coral individual. The bacterial community of <i>P. placomus</i> does not appear to include the genus <i>Endozoicomonas</i>, which has been found previously to be the dominant bacterial associate in several temperate and tropical gorgonians. Inferred functionality suggests the possibility of nitrogen cycling by the core bacterial community.