Meeting Abstract
Marine sponges frequently host symbiotic, unicellular cyanobacteria classified as Synechococcus spongiarum. Previous investigations used Sanger sequencing of the cyanobacterial16S-23S ribosomal RNA internal transcribed spacer (ITS) region to document 13 distinct clades of S. spongiarum. These clades are hypothesized to vary in host specificity from generalists to specialists, but the expense and labor involved in Sanger sequencing has limited replication across multiple geographic areas. We developed a high-throughput method to obtain ITS sequences using the Ion Torrent next-generation sequencing platform, multiplexing 61 specimens that represented 14 species from 6 locations, as well as positive (cloned sequences inserted into plasmid vectors) and negative controls. Quality filtering and analysis using the mothur pipeline identified 16,951 S. spongiarum sequences, which were subsequently clustered into the 13 known clades. Individual sponge specimens hosted an average of 2.6 S. spongiarum clades (ranging from 1 to 5 clades), while individual S. spongiarum clades occurred in 1 (Clade G) to 13 (Clade B) host sponge species. The relative abundance of clades hosted by some species varied significantly among locations; for example, Aplysina cauliformis hosted 99% Clade A in Martinique but only 33% Clade A in Panama. Similarly, Ircinia felix hosted 100% Clade J in Panama, but only 55% Clade J in the Bahamas and Martinique. These data suggest that selective pressures exerted by hosts and/or environmental conditions vary across the Caribbean. Future work will use this method to determine whether experimental manipulations of environmental conditions can change the relative abundance of S. spongiarum clades within individual hosts.
