Responses of bacterial strains isolated from drinking water environments to N-acyl-L-homoserine lactones and their analogs during biofilm formation

Often as a result of biofilm formation, drinking water distribution systems (DWDS) are regularly faced with the problem of microbial contamination. Quorum sensing (QS) systems play a marked role in the regulation of microbial biofilm formation; thus, inhibition of QS systems may provide a promising approach to biofilm formation control in DWDS. In the present study, 22 bacterial strains were isolated from drinking water-related environments. The following properties of the strains were investigated: bacterial biofilm formation capacity, QS signal molecule N-acyl-L-homoserine lactones (AHLs) production ability, and responses to AHLs and AHL analogs, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and 2(5H)-furanone. Four AHLs were added to developed biofilms at dosages ranging from 0.1?nmol·L^-1 to 100 nmol·L^-1. As a result, the biofilm growth of more than 1/4 of the isolates, which included AHL producers and non-producers, were significantly promoted. Further, the biofilm biomasses were closely associated with respective AHLs concentrations. These results provided evidence to support the idea that AHLs play a definitive role in biofilm formation in many of the studied bacteria. Meanwhile, two AHLs analogs demonstrated unexpectedly minimal negative effects on biofilm formation. This suggested that, in order to find an applicable QS inhibition approach for biofilm control in DWDS, the testing and analysis of more analogs is needed.