The role of bacterial biofilms and exudates on the settlement of mussel (Perna canaliculus) larvae

The ability of bacterial biofilms and biofilm exudates to induce mussel (Perna canaliculus) larvae to settle was investigated. Marine bacteria were isolated from marine seaweeds, seawater and mussels, and cultured in marine agar plates. Three main bacterial strains were selected, identified based on biochemical and 16 S rRNA techniques, and used for mussel settlement assays. Bacterial biofilms and biofilm exudates from Pseudoalteromonas sp. AMGP1 did not induce larval settlement in treatments, whereas biofilms and their exudates resulted in extremely high larval mortality. Thus, Pseudoalteromonas sp. AMGP1 biofilms may produce toxins deadly for P. canaliculus. Conversely, both Macrococcus sp. AMGM1 and Bacillus sp. AMGB1 significantly increased larval settlement (over 60%) compared with controls. These results suggest that settlement cues for P.canaliculus may be produced by the biofilm cells (and are present in the biofilm exudates), possibly as quorum sensing signals.