Reduction of mussel metamorphosis by inactivation of the bacterial thioesterase gene alteration of the fatty acid composition.

The molecular mechanism underlying modulation of metamorphosis of the bivalve by bacteria remains unclear. Here, the functional role of the thioesterase gene of the bacterium in larval metamorphosis was examined. The aim was to determine whether inactivation of the gene altered the biofilm-inducing capacity, bacterial cell motility, biopolymers, or the intracellular c-di-GMP levels. Complete inactivation of increased the c-di-GMP content in , accompanied by a reduced fatty acid content, weaker motility, upregulation of bacterial aggregation, and biofilm formation. The metamorphosis rate of mussel larvae on Δ biofilms was reduced by ∼ 80% compared with those settling on wild-type . Exogenous addition of a mixture of extracted fatty acids from into the Δ biofilms promoted the biofilm-inducing capacity. This study suggests that the bacterial thioesterase gene altered the fatty acid composition of Δ biofilms (BF) through regulation of its c-di-GMP, subsequently impacting mussel metamorphosis.