RESUMO
Swarming motility and hemolysis are virulence-associated determinants for a wide array of pathogenic bacteria. The broad host-range opportunistic pathogen Serratia marcescens produces serratamolide, a small cyclic amino-lipid, that promotes swarming motility and hemolysis. Serratamolide is negatively regulated by the transcription factors HexS and CRP. Positive regulators of serratamolide production are unknown. Similar to serratamolide, the antibiotic pigment, prodigiosin, is regulated by temperature, growth phase, HexS, and CRP. Because of this co-regulation, we tested the hypothesis that a homolog of the PigP transcription factor of the atypical Serratia species ATCC 39006, which positively regulates prodigiosin biosynthesis, is also a positive regulator of serratamolide production in S. marcescens. Mutation of pigP in clinical, environmental, and laboratory strains of S. marcescens conferred pleiotropic phenotypes including the loss of swarming motility, hemolysis, and severely reduced prodigiosin and serratamolide synthesis. Transcriptional analysis and electrophoretic mobility shift assays place PigP in a regulatory pathway with upstream regulators CRP and HexS. The data from this study identifies a positive regulator of serratamolide production, describes novel roles for the PigP transcription factor, shows for the first time that PigP directly regulates the pigment biosynthetic operon, and identifies upstream regulators of pigP. This study suggests that PigP is important for the ability of S. marcescens to compete in the environment.
Assuntos
Proteínas de Bactérias/genética , Depsipeptídeos/biossíntese , Regulação Bacteriana da Expressão Gênica , Prodigiosina/biossíntese , Serratia marcescens/genética , Fatores de Transcrição/genética , Proteínas de Bactérias/metabolismo , Depsipeptídeos/genética , Depsipeptídeos/farmacologia , Eritrócitos/efeitos dos fármacos , Teste de Complementação Genética , Hemólise/efeitos dos fármacos , Hexosiltransferases/genética , Hexosiltransferases/metabolismo , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Movimento/efeitos dos fármacos , Mutação , Óperon , Homologia de Sequência de Aminoácidos , Serratia marcescens/metabolismo , Transdução de Sinais , Fatores de Transcrição/metabolismoRESUMO
The bacterial species Serratia marcescens secretes both beneficial and cytotoxic proteins. Here we report that a crp mutant exhibited elevated secreted protease activity. A genetic screen revealed that the gene coding for the metalloprotease serralysin was necessary for the elevated proteolysis, and this was confirmed by western blot analysis. Proteomic analysis of secreted proteins corroborated increased secretion of serralysin protease by crp mutants compared to the wild type. The crp-mutant-secreted fractions also contained less chitinase and chitin binding protein. These data support the hypothesis that cAMP-CRP is an upstream indirect regulator of serralysin production and they provide novel insight into the S. marcescens secretome.
