Co-regulation of {beta}-lactam resistance, alginate production and quorum sensing in Pseudomonas aeruginosa.
Development of β-lactam resistance, production of alginate and modulation of virulence factor expression that alters host immune responses are the hallmarks of chronic Pseudomonas aeruginosa infection in cystic fibrosis patients. In this study, we propose that a co-regulatory network exists between these mechanisms. We compared the promoter activities of ampR, algT/U, lasR, lasI, rhlR, rhlI and lasA genes, representing the β-lactam antibiotic resistance master regulatory gene, the alginate switch operon, the las and rhl quorum-sensing (QS) genes, and the LasA staphylolytic protease, respectively. Four isogenic P. aeruginosa strains, the prototypic Alg(-) PAO1, Alg(-) PAOampR, the mucoid Alg(+) PAOmucA22 (Alg(+) PDO300) and Alg(+) PAOmucA22ampR (Alg(+) PDOampR) were used. We found that in the presence of AmpR regulator and β-lactam antibiotic, the extracytoplasmic function sigma factor AlgT/U positively regulated P(ampR), whereas AmpR negatively regulated P(algT/U). On the basis of this finding we suggest the presence of a negative feedback loop to limit algT/U expression. In addition, the functional AlgT/U caused a significant decrease in the expression of QS genes, whereas loss of ampR only resulted in increased P(lasI) and P(lasR) transcription. The upregulation of the las QS system is likely to be responsible for the increased lasA promoter and the LasA protease activities in Alg(-) PAOampR and Alg(+) PDOampR. The enhanced expression of virulence factors in the ampR strains correlated with a higher rate of Caenorhabditis elegans paralysis. Hence, this study shows that the loss of ampR results in increased virulence, and is indicative of the existence of a co-regulatory network between β-lactam resistance, alginate production, QS and virulence factor production, with AmpR playing a central role.
Balasubramanian
Deepak
D
Department of Biological Sciences, College of Arts and Science, Florida International University, Miami, FL 33199, USA.
Kong
Kok-Fai
KF
Department of Biological Sciences, College of Arts and Science, Florida International University, Miami, FL 33199, USA.
Jayawardena
Suriya Ravi
SR
Department of Biological Sciences, College of Arts and Science, Florida International University, Miami, FL 33199, USA.
Leal
Sixto Manuel
SM
Department of Biological Sciences, College of Arts and Science, Florida International University, Miami, FL 33199, USA.
Sautter
Robert Todd
RT
Department of Biological Sciences, College of Arts and Science, Florida International University, Miami, FL 33199, USA.
Mathee
Kalai
K
Department of Molecular Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA.
D000464:Alginates; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D017173:Caenorhabditis elegans / Q000382:microbiology; D004195:Disease Models, Animal; D024881:Drug Resistance, Bacterial; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D020723:Glucuronic Acid / Q000096:biosynthesis; D006603:Hexuronic Acids; D011401:Promoter Regions, Genetic; D011552:Pseudomonas Infections / Q000473:pathology; D011550:Pseudomonas aeruginosa / Q000472:pathogenicity / Q000502:physiology*; D053038:Quorum Sensing; D012808:Sigma Factor / Q000378:metabolism; D014774:Virulence; D037521:Virulence Factors / Q000096:biosynthesis; D018440:beta-Lactam Resistance; D047090:beta-Lactams / Q000378:metabolism
C079619:AlgU protein, Pseudomonas aeruginosa; D000464:Alginates; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006603:Hexuronic Acids; D012808:Sigma Factor; D037521:Virulence Factors; D047090:beta-Lactams; C071526:AmpR protein, Bacteria; D020723:Glucuronic Acid