The diversity of the bacterial communities associated with the azooxanthellate deep water octocoral Cirrhipathes lutkeni

This study examined the symbiotic microbiota of the hexacoral Cirrhipathes lutkeni using traditional plate culture, fluorescence in situ hybridization (FISH) and 16S rDNA characterization. FISH counts for the whole coral (holobiont) showed a major presence of gamma-Proteobacteria (22%) and Actinobacteria (19%), followed by alpha-Proteobacteria (14%), Firmicutes (9%), Cytophaga-Flavobacterium (7%), beta-Proteobacteria (6%) and Chloroflexi (2%). In contrast to the diversity observed by FISH, plate cultures were found to be selective for gamma-Proteobacteria (22 cultures) with the exception of an Actinobacterium. The methods employed in this study detected 76% of all microbes estimated by DAPI staining of C. lutkeni homogenates. The absence of zooxanthellae in this particular hexacoral was confirmed by PCR and spectrophotometry using fresh tissue isolated from the holobiont. This is the first study describing the microbial associations of shallow-water hexacorallia, which opens further insight into coral microbial ecology and may enhance the search for novel natural products in the near future.