N-acyl-homoserine lactone dynamics during biofilm formation of a 1,2,4-trichlorobenzene mineralizing community on clay

In Gram-negative bacteria, quorum sensing systems are based on the N-acyl-homoserine lactone (AHL) molecule. The objective of this study was to investigate the role of quorum sensing systems during biofilm formation by a microbial community while degrading the pollutant. Our model system included 1,2,4-trichlorobenzene (1,2,4-TCB) and its mineralizing Gram-negative bacterial community to investigate the relationships between AHL dynamics, cell growth and pollutant degradation. Biomineralization of 1,2,4-TCB was monitored for both the planktonic bacterial community with and without sterile clay particles in liquid cultures. The bacterial growth and production of AHLs were quantified by fluorescent in situ hybridization and immunoassay analysis, respectively. A rapid production of AHLs which occurred coincided with the biofilm formation and the increase of mineralization rate of 1,2,4-TCB in liquid cultures. There is a positive correlation between the cell density of Bodertella on the clay particles and mineralization rate of 1,2,4-TCB. 3-oxo-C_12:1-HSL appears to be the dominant AHL with the highest intensity and rapidly degraded by the bacterial community via two main consecutive reactions (lactone hydrolysis and decarboxylic reaction). These findings suggest that the integrated AHLs and their degraded products play a crucial role in biofilm formation and biomineralization of 1,2,4-TCB in culture.