Fatty acid-mediated signalling between twoPseudomonasspecies
We report the identification of fatty acids as mediators of intercellular signalling inPseudomonas putida, and betweenPseudomonas aeruginosaandP. putida. Tetradecanoic acid and fatty acids of similar chain length are present in supernatants of these strains and activate population density-dependent expression ofddcA, a gene involved in corn seed and root colonization byP. putidaKT2440. Consistently, significant amounts of these compounds were also found in corn root exudates. The signalling pathway involves the two-component regulatory system formed by RoxS and RoxR, which had been previously shown to control expression ofddcAand of a set of genes related to the redox balance ofP. putidacells. Production of the fatty acid signal inP. aeruginosais under the control of the LasI/LasR and RhlI/RhlR quorum sensing systems. Our data indicate that in terms of cell–cell communication,P. putidaKT2440 employs mechanisms closer to those of plant pathogens such asXanthomonasspp. and fungi likeCandida, which also rely on fatty acid derivatives.