Phylogenetic analysis and screening of antimicrobial and cytotoxic activities of culturable bacteria associated with the ascidian Botryllus schlosseri

Aims Isolating culturable bacteria associated with ascidian (Botryllus schlosseri) and investigating their bioactivities to discover new marine microbial resources with potential to produce novel bioactive natural products. Methods and Results A total of 357 bacteria were isolated from the ascidian B. schlosseri from the coast of Weihai in the north Yellow Sea, China. Of these, 203 isolates were identified by 16S rRNA gene sequencing and they belonged to 52 genera from 30 families in five phyla. The antimicrobial activities and cytotoxic activities of all isolates were determined. Of the 357 isolates, 135 isolates demonstrated antimicrobial activities, and the crude extracts of five isolates showed strong cytotoxicity against human hepatocellular carcinoma Bel 7402 or human cervical carcinoma HeLa cells. Conclusions Our study revealed the diversity of bacteria associated with the ascidian B. schlosseri and reported a broad spectrum of antimicrobial and cytotoxic activities displayed by these isolates. Significance and Impact of the Study Our results suggest that the culturable bacteria associated with the ascidian B. schlosseri may be a potential source for novel bioactive compounds.