Adsorption of N-acyl-Homoserine Lactone onto Colloidal Minerals Presents Potential Challenges for Quorum Sensing in the Soil Environment

Bacterial interspecies and intraspecies communications are mediated by diffusible signaling molecules. In complex natural environments, the fluctuation of geochemical and physical conditions presents substantial challenges to the environmental fate of N-acyl-homoserine lactones. Although researchers have attempted to elucidate the influence of aquatic environmental parameters on bacterial QS signals, insufficient information is known regarding their interactions with soil. Thus, the adsorption of N-(3-oxododecanoyl) homoserine lactone on three common soil minerals (montmorillonite, kaolinite, and goethite) was investigated by performing batch studies coupled with Fourier-transform infrared spectroscopy and isothermal titration calorimetry. The adsorption isotherms of N-(3-oxododecanoyl) homoserine lactone on these minerals conformed to the Langmuir equation; the adsorbed N-(3-oxododecanoyl) homoserine lactone amount increased significantly as electrolyte concentration increased from 0.001mol L-1 to 0.1mol L-1. The adsorption of N-(3-oxododecanoyl) homoserine lactone on goethite was enhanced with increasing pH values; by contrast that on montmorillonite and kaolinite showed less dependence in the 6.0-8.0pH range. Hydrogen bonding and hydrophobic interaction had important functions in these processes. This study provided insights into the distribution and diffusion of N-acyl-homoserine lactone in soil and associated environments.