Quorum-sensing-negative (lasR) mutants of Pseudomonas aeruginosa avoid cell lysis and death.

@article{citeulike:1185894, abstract = {In Pseudomonas aeruginosa, N-acylhomoserine lactone signals regulate the expression of several hundreds of genes, via the transcriptional regulator LasR and, in part, also via the subordinate regulator RhlR. This regulatory network termed quorum sensing contributes to the virulence of P. aeruginosa as a pathogen. The fact that two supposed PAO1 wild-type strains from strain collections were found to be defective for LasR function because of independent point mutations in the lasR gene led to the hypothesis that loss of quorum sensing might confer a selective advantage on P. aeruginosa under certain environmental conditions. A convenient plate assay for LasR function was devised, based on the observation that lasR mutants did not grow on adenosine as the sole carbon source because a key degradative enzyme, nucleoside hydrolase (Nuh), is positively controlled by LasR. The wild-type PAO1 and lasR mutants showed similar growth rates when incubated in nutrient yeast broth at pH 6.8 and 37 degrees C with good aeration. However, after termination of growth during 30 to 54 h of incubation, when the pH rose to > or = 9, the lasR mutants were significantly more resistant to cell lysis and death than was the wild type. As a consequence, the lasR mutant-to-wild-type ratio increased about 10-fold in mixed cultures incubated for 54 h. In a PAO1 culture, five consecutive cycles of 48 h of incubation sufficed to enrich for about 10\% of spontaneous mutants with a Nuh(-) phenotype, and five of these mutants, which were functionally complemented by lasR(+), had mutations in lasR. The observation that, in buffered nutrient yeast broth, the wild type and lasR mutants exhibited similar low tendencies to undergo cell lysis and death suggests that alkaline stress may be a critical factor providing a selective survival advantage to lasR mutants.}, address = {D\'{e}partement de Microbiologie Fondamentale, Bātiment de Biologie, Universit\'{e} de Lausanne, Switzerland.}, author = {Heurlier, K. and D\'{e}nervaud, V. and Haenni, M. and Guy, L. and Krishnapillai, V. and Haas, D. }, citeulike-article-id = {1185894}, doi = {http://dx.doi.org/10.1128/JB.187.14.4875-4883.2005}, issn = {0021-9193}, journal = {J Bacteriol}, keywords = {autolysis, biofilm, cooperation, quorum-sensing}, month = {July}, number = {14}, pages = {4875--4883}, posted-at = {2007-03-25 07:01:00}, priority = {5}, title = {Quorum-sensing-negative (lasR) mutants of Pseudomonas aeruginosa avoid cell lysis and death.}, url = {http://dx.doi.org/10.1128/JB.187.14.4875-4883.2005}, volume = {187}, year = {2005} }

TY - JOUR ID - citeulike:1185894 L3 - citeulike-article-id:1185894 TI - Quorum-sensing-negative (lasR) mutants of Pseudomonas aeruginosa avoid cell lysis and death. JF - J Bacteriol VL - 187 IS - 14 SP - 4875 EP - 4883 AD - Département de Microbiologie Fondamentale, Bātiment de Biologie, Université de Lausanne, Switzerland. SN - 0021-9193 N2 - In Pseudomonas aeruginosa, N-acylhomoserine lactone signals regulate the expression of several hundreds of genes, via the transcriptional regulator LasR and, in part, also via the subordinate regulator RhlR. This regulatory network termed quorum sensing contributes to the virulence of P. aeruginosa as a pathogen. The fact that two supposed PAO1 wild-type strains from strain collections were found to be defective for LasR function because of independent point mutations in the lasR gene led to the hypothesis that loss of quorum sensing might confer a selective advantage on P. aeruginosa under certain environmental conditions. A convenient plate assay for LasR function was devised, based on the observation that lasR mutants did not grow on adenosine as the sole carbon source because a key degradative enzyme, nucleoside hydrolase (Nuh), is positively controlled by LasR. The wild-type PAO1 and lasR mutants showed similar growth rates when incubated in nutrient yeast broth at pH 6.8 and 37 degrees C with good aeration. However, after termination of growth during 30 to 54 h of incubation, when the pH rose to > or = 9, the lasR mutants were significantly more resistant to cell lysis and death than was the wild type. As a consequence, the lasR mutant-to-wild-type ratio increased about 10-fold in mixed cultures incubated for 54 h. In a PAO1 culture, five consecutive cycles of 48 h of incubation sufficed to enrich for about 10% of spontaneous mutants with a Nuh(-) phenotype, and five of these mutants, which were functionally complemented by lasR(+), had mutations in lasR. The observation that, in buffered nutrient yeast broth, the wild type and lasR mutants exhibited similar low tendencies to undergo cell lysis and death suggests that alkaline stress may be a critical factor providing a selective survival advantage to lasR mutants. KW - autolysis KW - biofilm KW - cooperation KW - quorum-sensing AU - Heurlier, K AU - Dénervaud, V AU - Haenni, M AU - Guy, L AU - Krishnapillai, V AU - Haas, D PY - 2005/07// UR - http://dx.doi.org/10.1128/JB.187.14.4875-4883.2005 ER -