Abstract: The two bacterial strains with quorum sensing isolated from spoiled sea bass were identified based on 16S rRNA gene sequence analysis as Hafnia alvei-14 and Serratia marcescens-01 with the ability to produce prodigiosin, respectively. The production of the quorum-sensing signal molecules N-acyl homoserine lactones (AHLs) and biofilm formation in S. marcescens-01 were investigated when co-cultured with H. alvei-14 under different culture conditions. The results showed that co-culture with H. alvei could promote AHLs secretion and biofilm production in S. marcescens, which might be related to quorum sensing. Changes in environmental conditions were the important factors that could affect the secretion of AHLs and biofilm formation. Higher salt concentration and too low or too high pH values were unfavorable to microbial secretion of AHLs and biofilm formation, while restrictive carbon and nitrogen sources could stimulate the quorum sensing system and promote the release of AHLs and biofilm formation.

Key words: Hafnia alvei, Serratia marcescens, co-culture, quorum sensing