Comparative analysis of Bacteria communities in the Hawaiian reef-building corals Porites compressa and P. lobata

This study focused on the Bacteria community richness and structure found in the mucus layer of different hermatypic coral species by examination of 16S rRNA gene fragments amplified from community DNA extracted from adjacent coral colonies on a reef transect at Olowalu, Maui. The broad aim included developing foundational knowledge of microbial communities associated with the mucus secreted by the corals Porites lobata and P. compressa. The goals were to (i) determine if similarities exist within and between coral mucus microbial assemblages, (ii) develop and produce diagnostic tools targeted at specific microbial groups, and (iii) test the efficacy of these tools on coral mucus samples. This project provides evidence of a potentially new symbiotic relationship between at least two members of the coral genus Porites, and a putative Oceanospirillum sp. identified here as an operational taxonomic unit (OTU) termed C7-A01.;Preliminary work showed discrete microbial communities on Pocillopora meandrina mucus compared to commensal hermit crabs, Calcinus obscurus, and adjacent seawater. Each of these samples hosted phylogenetically distinct Bacteria, regardless of the method employed. No Bacteria cultivated from any of the three sample types were detected in 16S rRNA gene fragment clone libraries prepared from the same samples. These findings indicate that use of a polyphasic approach is essential when generating a comprehensive measurement of microbial diversity in coral mucus.;The Bacteria communities among and between the two species of Porites and surrounding seawater were highly variable. The level of OTU richness exhibited within the coral mucus was uneven, in some cases satisfying theoretical rarefaction and richness calculations. Relatively low species richness was observed in two of the P. lobata samples and one seawater sample though no inhibition in the polymerase chain reaction (PCR) was demonstrated.;Fluorescent oligonucleotide probes based on sequences generated from clone libraries were used as a presence/absence indicator of selected OTUs found to be unique to three or more corals from the same species. The probe results and clone library results disagreed in many instances, yet demonstrated the potential for this method to be used as a tool to check for specific OTUs in coral mucus.