Diversity and antibacterial activity of bacteria cultured from Mediterranean Axinella spp. sponges

Aims Evaluation of the diversity and antibacterial activity of bacteria cultivated from Mediterranean Axinella sponges and investigating the influence of culture conditions on antibacterial activity profiles of sponge bacteria. Methods and Results Based on 16S rRNA gene sequence analysis, the 259 bacteria isolated from the three Mediterranean Axinella sponges A. cannabina, A. verrucosa and A. polypoides belonged to 41 genera from the four phyla Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria and included five potential newly cultured genera. In antagonistic streak assays, 87 isolates (34%) from 13 genera showed antibacterial activity towards at least one of the 10 environmental and laboratory test bacteria. The extracts and filtrates of 22 isolates grown under three different culture conditions were less often active as the isolates in the corresponding antagonistic streak assays. Changes in antibacterial activity profiles were isolate- and culture condition-specific. Conclusions Axinella sponges are a good source to cultivate phylogenetic diverse and hitherto novel bacteria, many of which with antibacterial activity. Analysis of induced antibacterial activities might enhance the role of sponge bacteria in efforts to isolate new antibiotics in the future. Significance and Impact of the Study This study was the first to investigate the diversity and antibacterial activity of bacteria isolated from A. cannabina and A. verrucosa. It highlights the potential importance of induced activity and the need for employing multiple culture conditions in antibacterial screening assays of sponge-associated bacteria.