Liberate and grab it, ingest and digest it: the GbdR regulon of the pathogen Pseudomonas aeruginosa

Transcriptional Regulators Controlling Virulence in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a pathogen capable of colonizing virtually every human tissue. The host colonization competence and versatility of this pathogen are powered by a wide array of virulence factors necessary in different steps of the infection process. This includes factors involved in bacterial motility and attachment, biofilm formation, the production and secretion of extracellular invasive enzymes and exotoxins, the production of toxic secondary metabolites, and the acquisition of iron. Expression of these virulence factors during infection is tightly regulated, which allows their production only when they are needed. This process optimizes host colonization and virulence. In this work, we review the intricate network of transcriptional regulators that control the expression of virulence factors in P. aeruginosa, including one- and two-component systems and σ factors. Because inhibition of virulence holds promise as a target for new antimicrobials, blocking the regulators that trigger the production of virulence determinants in P. aeruginosa is a promising strategy to fight this clinically relevant pathogen.

Pseudomonas aeruginosa gbdR gene is transcribed from a σ54-dependent promoter under the control of NtrC/CbrB, IHF and BetI

Pseudomonasaeruginosa uses choline as a source of carbon and nitrogen, and also for the synthesis of glycine betaine, an osmoprotectant under stress conditions such as drought and salinity. The transcription factor GbdR is the specific regulator of choline metabolism and it belongs to the Arac/XylS family of transcriptional regulators. Despite the link between choline catabolism and bacterial pathogenicity, gbdR regulation has not been explored in detail. In the present work, we describe how gbdR transcription can be initiated from a σ54-dependent promoter. gbdR transcription can be activated by NtrC in the absence of a preferential nitrogen source, by CbrB in the absence of a preferential carbon source, and by the integration host factor favouring DNA bending. In addition, we found that BetI negatively regulates gbdR expression in the absence of choline. We identified two overlapping BetI binding sites in the gbdR promoter sequence, providing an additional example of σ54-promoter down-regulation. Based on our findings, we propose a model for gdbR regulation and its impact on choline metabolism.

Genome-Wide Analysis of Oceanimonas sp. GK1 Isolated from Gavkhouni Wetland (Iran) Demonstrates Presence of Genes for Virulence and Pathogenicity

OBJECTIVE

The bacterium Oceanimonas sp. (O. sp.) GK1 is a member of the Aeromonadaceae family and its genome represents several virulence genes involved in fish and human pathogenicity. In this original research study we aimed to identify and characterize the putative virulence factors and pathogenicity of this halotolerant marine bacterium using genome wide analysis.

MATERIALS AND METHODS

The genome data of O. sp. GK1 was obtained from NCBI. Comparative genomic study was done using MetaCyc database.

RESULTS

Whole genome data analysis of the O. sp. GK1 revealed that the bacterium possesses some important virulence genes (e.g. ZOT, RTX toxin, thermostable hemolysin, lateral flagella and type IV pili) which have been implicated in adhesion and biofilm formation and infection in some other pathogenic bacteria.

CONCLUSION

This is the first report of the putative pathogenicity of O. sp.GK1. The genome wide analysis of the bacterium demonstrates the presence of virulence genes causing infectious diseases in many warmand cold-blooded animals.