ERWIN, Patrick M.*; THACKER, Robert W.; University of Alabama at Birmingham; University of Alabama at Birmingham: Characterization and Structure of Sponge-Associated Microbial Communities

Marine sponges harbor a diverse assemblage of microbial symbionts. Molecular techniques are instrumental in the identification of sponge-associated bacteria and analysis of the stability and structure of sponge microbial communities. We constructed a 16S ribosomal DNA clone library for five sponge species inhabiting gas rig pilings in the northern Gulf of Mexico, focusing on the dominant sponge species Hymeniacidon heliophila. For each sample, 15 bacterial clones were isolated and sequenced. A total of 20 samples were examined for the five species. Three alpha-proteobacteria and 2 beta-proteobacteria species accounted for nearly half (45%) of all clones recovered. Similarity matrices were constructed to compare bacterial communities between species and analyzed statistically using analyses of similarity (ANOSIM) and multi-dimensional scaling (MDS) plots. Operational taxonomic units (OTUs) were defined using 95% and 99% sequence identity, resulting in 63 and 85 unique bacterial clades, respectively. Under both OTU criteria, different sponge species housed significantly different bacterial communities with individuals of the same species exhibiting similar community structure. The sponge species studied here possessed structured microbial communities dominated by one or two unique bacterial clades.