Analysis of bacterial composition in marine sponges reveals the influence of host phylogeny and environment

Bacterial communities associated with sponges are influenced by environmental factors; however, some degree of genetic influence of the host on the microbiome is also expected. In this work, 16S rRNA gene amplicon sequencing revealed diverse bacterial phylotypes based on the phylogenies of three tropical sponges (Aplysina fulva, Aiolochroia crassa and Chondrosia collectrix). Despite their sympatric occurrence, the studied sponges presented different bacterial compositions that differed from those observed in seawater. However, lower dissimilarities in bacterial communities were observed within sponges from the same phylogenetic group. The relationships between operational taxonomic units (OTUs) recovered from the sponges and database sequences revealed associations among sequences from unrelated sponge species and sequences retrieved from diverse environmental samples. In addition, one Proteobacteria OTU retrieved from A. fulva was identical to sequences previously reported from A. fulva specimens collected along the Brazilian coast. Based on these results, we conclude that bacterial communities associated with marine sponges are shaped by host identity, while environmental conditions seem to be less important in shaping symbiont communities. This is the first study to assess bacterial communities associated with marine sponges in the remote St. Peter and St. Paul Archipelago using amplicon sequencing of the 16S rRNA gene.