Microbial community composition of black band disease on the coral host Siderastrea siderea from three regions of the wider Caribbean

Microbial communities associated with black band disease (BBD) on colonies of the reef building coral Siderastrea siderea from reefs in 3 regions of the wider Caribbean were studied using 16S rRNA gene-targeted amplification, cloning, and sequencing. Samples were collected from 7 BBD-infected S. siderea colonies on 2 reefs near Lee Stocking Island, Bahamas, one reef in the Florida Keys, Florida, USA, and 2 reefs in St. Croix, US Virgin Islands. Genomic DNA extracted from BBD samples was PCR-amplified with universal bacterial primers (27F and 1492R). Seven clone libraries were constructed and 411 sequences were retrieved. All of the clone libraries were dominated by Alphaproteobacteria and contained sequences associated with bacteria of the sulfur cycle, including the first report of the molecular detection of sequences related to the sulfide-oxidizing genus Beggiatoa in BBD field samples. Additionally, all clone libraries had sequence types of bacteria associated with toxin producing dinoflagellates. These sequences were most abundant in a sewage impacted reef site in St. Croix, which also had the highest prevalence of BBD-infected colonies. Non-metric multidimensional scaling and cluster analysis showed clustering of BBD microbial communities by relative level of anthropogenic impact. The results support the hypothesis that BBD is composed of variable members of distinct physiological and toxin associated bacterial groups and that the microbial community variation is associated with environmental differences such as anthropogenic impact. We propose that with degrading water quality (i.e. increasing nutrients) certain proteobacteria thrive and increase BBD virulence.