Florida reef sponges harbor coral disease-associated microbes

Sponges can filter large volumes of seawater and accumulate highly diverse and abundant microbial communities within their tissue. Culture-independent techniques such as fluorescent in situ hybridization (FISH), 16S small subunit (SSU) rRNA gene analyses, and transmission electron microscopy (TEM) were applied to characterize the presence and distribution of microbes within sponges abundant on south Florida reefs. This study found that coral disease-associated bacteria (CDAB) are harbored within Agelas tubulata and Amphimedon compressa. FISH probes detected several potential bacterial pathogens such as Aurantimonas coralicida, Cytophaga sp., Desulfovibrio spp, Serratia marcescans, and Vibrio mediterranei within A. compressa and A. tubulata host sponges. Spatial differences in the distribution of targeted bacteria were seen within sponge hosts. Transmission electron microscopy of A. compressa indicated there was a higher concentration of bacteria in the choanosome compared to the ectosome. These observed spatial distributions support the presence of internal sponge niches, which could play a role in the location of the CDAB within the sponges.