Identification of N-Hexadecanoyl-L-homoserine lactone (C16-AHL) as signal molecule in halophilic bacterium Halomonas smyrnensis AAD6

Quorum sensing (QS) mechanism regulates a variety of vital functions such as motility, growth inhibition, biofilm development, virulence expression and plasmid conjugation. Many of these activities are essential for the well-being of organisms, in particular in extreme conditions as hypersaline environments. Halophiles are able to synthesize products that are stable and exploit their activities under such "extreme" conditions, namely saline environments such as marine habitat, salt lakes, brines and saline soils. The versatility of these products lead researchers to address their interest to their biotechnological applications. In this study, QS activity of Halomonas smyrnensis AAD6, a moderately halophilic and exopolysaccharide-producing bacterium was investigated. Dichloromethane extracts from stationary phase cultures of Halomonas smyrnensis AAD6 were partially purified and C16-AHL was identified by LC-MS analysis. The synthesis of autoinducers was assayed and their production was detected starting from 48h of growth. The growth-phase dependent exopolysaccharide (EPS) and signal molecule production suggested that these activities could be linked.