Antibacterial and bioiflm inhibitory activities of bacteria associated with polychaetes

Objective:To study the antibacterial and antibiofilm activities expressed by epibiotic bacteria associated with the polychaetes Platynereis dumerilii and Syllis sp.Methods:A total of 32 cultivable bacterial strains were isolated from the two polychaete species.The crude extracts were tested for antibacterial activity and biofilm inhibitory activity against pathogenic and biofilm-forming bacterial strains.Extracts of the strains which showed strong activity were analyzed by thin-layer chromatography(TLC)and the bacterial strains were identified based on 16S rRNA gene sequencing.Results:Extracts of 13 bacterial strains showed inhibitory activity against pathogenic and biofilm-forming bacteria.The crude extracts also affected the synthesis of extracellular polymeric substances and cell surface hydrophobicity of the Alteromonas sp.isolated from marine biofilm.The adhesion of Alteromonas sp.on glass surface showed significant variation between surface-associated bacterial crude extract treatment and control groups.Among the 13 bacteria,two strains PA8 and PA19 were further analyzed for bioactive fractions.Thinlayer chromatography indicated the presence of a single active fraction in the crude extract of both the bacterial strains.The epibiotic bacterial strains P8 and P19 were identified as Exiguobacterium sp.and Actinobacterium sp.respectively based on 16S rRNA gene sequencing.Conclusions:The present study indicates that bacteria associated with marine invertebrates inhabiting the coastal waters could be used as a potential source for the isolation of bioactive metabolites.