High Frequency of Morphotypical Diversification In Pseudomonas aeruginosa mutS Populations Is Related to Quorum Sensing

LUJAN ADELA; SEGURA IGNACIO; MOYANO ALEJANDRO; ARGARAÑA CARLOS; SMANIA ANDREA

Iguazu, Misiones, Argentina

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2004

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Pseudomonas aeruginosa is an extraordinarily versatile species involved in severe and often fatal infection in Cystic Fibrosis, AIDS or severe burn wounds patients. Its pathogenicity is based on the production and secretion of extracellular virulence factors whose expression is tightly regulated by quorum-sensing (QS) systems that are hierarchically controlled by global regulators. We recently described that, in contrast to the parental strain, when a hypermutator P. aeruginosa mutant was grown for a short period in LB medium, it reproducibly generated two morphotypes in a high frequency, mS1 and mS2 (Microbiology, 150:1327-1338, 2004). Notably, mS2 displayed differences in virulence traits, including antibiotic resistance, altered motility behavior, hyperpigmentation, reduced protease activity and non-cytotoxic invasive phenotype, suggesting that they stem from mutations in major regulators related to QS. In this work we strengthen this hypothesis using a Caenorhabditis elegans-P.aeruginosa pathogenesis model. The mS1 and mS2 variants were tested for virulent/nonvirulent phenotypes in comparison with gacA and lasR mutants. As described for the global regulator GacA and for the QS regulator LasR, mS2 failed to kill C.elegans in slow and paralitic assays. For exoprotease and elastaseB production, mS2 was similar to gacA and lasR mutants, although its hyperpigmentation and swarming motility were equivalent to lasR. Our results indicate that mS2 variant is affected in QS regulators and suggest that in P. aeruginosa, hipermutability could constitute an adaptive strategy by modulating virulence.