Involved in the synthesis of the acyl-homoserine lactone (AHL) signal N-(3-hydroxydodecanoyl)-L-HSL (3-hydroxy-C(12)-HSL or OH-dDHL). Required for normal biofilm development. a fatty acyl-[ACP] + S-adenosyl-L-methionine = an N-acyl-L-homoserine lactone + H(+) + holo-[ACP] + S-methyl-5'-thioadenosine Expression is activated by AHL signals in a positive-feedback loop. Mutant fails to produce any detectable AHL signals and is impaired in biofilm development. Belongs to the autoinducer synthase family.