Characteristics of N-Acylhomoserine Lactones Produced by Hafnia alvei H4 Isolated from Spoiled Instant Sea Cucumber.

This study aimed to identify -acylhomoserine lactone (AHL) produced by H4, which was isolated from spoiled instant sea cucumber, and to investigate the effect of AHLs on biofilm formation. Two biosensor strains, CV026 and KYC55, were used to detect the quorum sensing (QS) activity of H4 and to confirm the existence of AHL-mediated QS system. Thin layer chromatography (TLC) and high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS) analysis of the AHLs extracted from the culture supernatant of H4 revealed the existence of at least three AHLs: -hexanoyl-l-homoserine lactone (C6-HSL), -(3-oxo-octanoyl)-l-homoserine lactone (3-oxo-C8-HSL), and -butyryl-l-homoserine lactone (C4-HSL). This is the first report of the production of C4-HSL by . In order to determine the relationship between the production of AHL by H4 and bacterial growth, the β-galactosidase assay was employed to monitor AHL activity during a 48-h growth phase. AHLs production reached a maximum level of 134.6 Miller unites at late log phase (after 18 h) and then decreased to a stable level of about 100 Miller unites. AHL production and bacterial growth displayed a similar trend, suggesting that growth of H4 might be regulated by QS. The effect of AHLs on biofilm formation of H4 was investigated by adding exogenous AHLs (C4-HSL, C6-HSL and 3-oxo-C8-HSL) to H4 culture. Biofilm formation was significantly promoted ( < 0.05) by 5 and 10 µM C6-HSL, inhibited ( < 0.05) by C4-HSL (5 and 10 µM) and 5 µM 3-oxo-C8-HSL, suggesting that QS may have a regulatory role in the biofilm formation of H4.