Antimicrobial activity and diversity of bacteria associated with Taiwanese marine sponge Theonella swinhoei

Marine sponges often rely on other epiphytes for protection from harmful predators. To understand the diversity and antimicrobial activity present among epiphytic bacteria isolated from marine sponge. We used both the 16S rRNA tag pyrosequencing method and the culture-based method to investigate the bacterial communities of Theonella swinhoei collected off the shore of southern Taiwan. Eight-hundred and eighteen operational taxonomic units (OTUs; 97% sequence similarity) were identified from 23,700 sponge-derived sequence tags. The bacteria associated with T. swinhoei were found to be highly diverse—as many as 12 different phyla of bacteria were identified. However, in terms of population evenness, the community was dominated by two phyla—Acidobacteria (71.54%) and Chloroflexi (19.60%). A total of 700 bacterial strains were isolated and cultured from samples of the sponge T. swinhoei. Within these culturable strains, only 12% were Actinomycetes. Despite the low percentage of Actinobacteria from the samples, among the 51 strains of culturable bacteria that showed high antimicrobial activity, a great majority (62%) were Actinomycetes (30 strains of Streptomyces and 1 strain each of Micromonospora and Brevibacterium). The remaining isolates that produced antimicrobial compounds were Gammaproteobacteria (10 strains of Pseudoalteromonas) and Firmicutes (8 and 1 strains of Bacillus and Paenibacillus, respectively). We speculated that many more Actinomycetes are yet to be isolated from T. swinhoei microbiota. Advanced techniques, such as high-throughput culture and culturome, should allow the isolation and purification of these medically important groups of bacteria from sponge.