Pyrosequencing of bacterial symbionts within Axinella corrugata sponges: Diversity and seasonal variability

Marine sponge species are of significant interest to many scientific fields including marine ecology, conservation biology, genetics, host-microbe symbiosis and pharmacology. One of the most intriguing aspects of the sponge “holobiont” system is the unique physiology and interaction with microbes from the marine environment and the development of a complex commensal microbial community, yet intraspecific variability and temporal stability of sponge-associated bacterial symbionts remain relatively unknown. We have characterized the bacterial symbiont communities of seven different individuals of the Caribbean reef sponge Axinella corrugata, from two different Florida reef locations during variable seasons using multiplex 454 pyrosequencing of 16S rRNA amplicons. Utilizing versatile bioinformatics methods and analytical software, we have identified over 9,000 distinct bacterial operational taxonomic units. Differentially abundant classes between seasonal Axinella communities included Gammaproteobacteria, Flavobacteria, Alphaproteobacteria, Cyanobacteria, Acidobacter and Nitrospira. This study has identified approximately 330 A. corrugata-specific symbiotic OTUs, many of which are related to the sulfur-oxidizing Ectothiorhodospiraceae. This family appeared exclusively within A. corrugata, comprising >34.5% of all sequenced amplicons. Other A. corrugata symbionts such as Deltaproteobacteria, Bdellovibrio, and Thiocystis among many others are described. Slight shifts in several bacterial taxa were observed between communities sampled during spring and fall seasons. New 16S rDNA sequences and concomitant identifications greatly expand the microbial community profile for this model reef sponge, and will likely be useful as a baseline for any future comparisons regarding sponge microbial community dynamics.