Diversity Of Bacteria Associated With Ascidians From Wei Hai And Screening Of Strains With Bioactivities

Ascidian is one of the main marine animals from which many kinds of marinenatural products are isolated. Ascidians are filter feeders and are associated with diversepopulations of microorganisms. Therefore, isolation of microorganism from ascidians isan important way to obtain and develop the marine microorganism. Ascidian resourcesin Weihai area are very rich. The natural products and microorganism isolated fromdifferent kinds of ascidians are different. Therefore, the development of ascidians andmicroorganism associated with ascidians from Weihai is a good way to find new naturalproducts.Culture-dependent method was used to isolate bacteria associated with ascidians ofBotrylloides sp., Styela clava and Ciona intestinalis from Weihai in Shandong pronivce.The identification and phylogenetic analysis of the isolated bacteria were determined by16S rRNA sequencing. The potential antimicrobial activities of the isolated bacterialstrains for different indicator strains were screened. MTT analysis was performed todetermine the potential cytotoxic activity of the crude extract of the isolated bacteria.A total of181bacterial strains were isolated from3kinds of ascidians.61bacterialstrains isloated from Botrylloides sp, and53bacterial strains isloated from Styela clava,and67bacterial strains isloated from Cinoa intestinalis.150bacterial strains weresequenced for their16S rRNA to analyze their phylogenetic positions. Our resultsindicated that there was some difference in the diversity of bacteria associated withthese3kinds of ascidians. The bacteria associated with Botrylloides sp. were belongedto25species of8genera of6families in3phylum (Firmicutes, Proteobacteria andActinobacteria). The bacteria associated with Styela clava were belonged to21speciesof4genera of4families in3phylum (Firmicutes, Proteobacteria and Actinobacteria).The bacteria associated with Ciona intestinalis were belonged to12species of3generaof2families in2phylum (Firmicutes and Proteobacteria). Bacillus was the dominantbacteria of Firmicutes, and bacterial strains of Proteobacteria were all belonged toγ-Proteobacteria, and Streptomyces was the dominant actinomycetes in Actinobacteria.A total of80of150bacterial strains (53.3%strains) showed potent activitiesagainst Gram-negative bacteria, Gram-positive bacteria, human pathogenic fungi andaquatic animal pathogenic bacteria. Of80bacterial strains with activities,69%strains with activities were mainly belonged to Bacillus of Firmicutes, and some10%strainsaffiliated with Streptomyces.The crude extracts from42bacterial strains (of150bacterial strains) exhibitedcytotoxic activity against human breast tumor cells MCF-7.Our results suggest that the diversity of bacteria associated with ascidian isabundant and may be developed as promising sources for the discovery of novelbioactive substances.