Study on the Acyl-Homoserine Lactone Production of a Gram-Negative Bacterium Sphingomonas xenophaga by Co-Cultivation with Variovorax paradoxus

Abstract

Acyl-homoserine lactone is one of the signal molecules produced for the cell-to-cell communication in Gram-negative bacteria. When bacteria reach the high cell density at a threshold level, they produce acyl-homoserine lactone. Acyl-homoserine lactone can bind to the receptor and then induce the target gene expressions resulting in the decrease of the bacterial populations. From the co-cultivation of Sphingomonas xenophaga that can produce acyl-homoserine lactone and Variovorax paradoxus that can utilize acyl-homoserine lactone as an energy source, it was found that the optimum conditions for cocultivation both bacteria were LB medium and incubation temperature at 20^oC. In addition, V. paradoxus could degrade acyl-homoserine lactone produced from S. xenophaga as an energy source resulting in the increase of the 2-fold higher growth rate. The slower death of S. xenophaga by co-cultivation is due to the decrease of acyl-homoserine lactone level.