Identification of the alternative sigma factor SigX regulon and its implications for Pseudomonas aeruginosa pathogenicity.

ABSTRACT: Pseudomonas aeruginosa is distinguished by its broad metabolic diversity and its remarkable capability for adaptation, which relies on a large collection of transcriptional regulators and alternative sigma (?) factors. The largest group of alternative ? factors is that of the extracytoplasmic function (ECF) ? factors, which control key transduction pathways for maintenance of envelope homeostasis in response to external stress and cell growth. In addition, there are specific roles of alternative ? factors in regulating the expression of virulence and virulence-associated genes. Here, we analyzed a deletion mutant of the ECF ? factor SigX and applied mRNA profiling to define the SigX-dependent regulon in P. aeruginosa in response to low-osmolarity-medium conditions. Furthermore, the combination of transcriptional data with chromatin immunoprecipitation (ChIP) followed by high-throughput sequencing (ChIP-seq) led to the identification of the DNA binding motif of SigX. Genome-wide mapping of SigX-binding regions revealed enrichment of downstream genes involved in fatty acid biosynthesis, type III secretion, swarming and cyclic di-GMP (c-di-GMP) signaling. In accordance, a sigX deletion mutant exhibited altered fatty acid composition of the cell membrane, reduced cytotoxicity, impaired swarming activity, elevated c-di-GMP levels, and increased biofilm formation. In conclusion, a combination of ChIP-seq with transcriptional profiling and bioinformatic approaches to define consensus DNA binding sequences proved to be effective for the elucidation of the regulon of the alternative ? factor SigX, revealing its role in complex virulence-associated phenotypes in P. aeruginosa.

SUBMITTER: Blanka A 

PROVIDER: S-EPMC3911239 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature