Antidiatom activity of marine bacteria associated with sponges from San Juan Island, Washington

Crude extracts of 52 marine bacteria associated with sponges, which were collected from the sea near San Juan Island, Washington, USA, were screened using diatom attachment assays against Amphora sp., Nitzschia closterium, Sellaphora sp. and Stauroneis sp. to investigate their antidiatom activities. Among these samples, five expressed strong anti-adhesion effects on all four tested diatoms. There was no negative effect observed from those five active samples on the growth of Amphora sp. Those five active samples were prepared from respective isolates, which all belonged to the genus Bacillus based on 16S rRNA gene sequencing analysis. The results of present study indicate that Bacillus may play important roles for sponges' chemical defence against biofouling of diatoms and that the metabolites of Bacillus may be a potential source of natural antifouling compounds.