Analysis of Pseudomonas aeruginosa diguanylate cyclases and phosphodiesterases reveals a role for bis-(3′-5′)-cyclic-GMP in virulence

Abstract

The opportunistic pathogen Pseudomonas aeruginosa is responsible for systemic infections in immunocompromised individuals and chronic respiratory disease in patients with cystic fibrosis. Cyclic nucleotides are known to play a variety of roles in the regulation of virulence-related factors in pathogenic bacteria. A set of P. aeruginosa genes, encoding proteins that contain putative domains characteristic of diguanylate cyclases (DGCs) and phosphodiesterases (PDEs) that are responsible for the maintenance of cellular levels of the second messenger bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) was identified in the annotated genomes of P. aeruginosa strains PAO1 and PA14. Although the majority of these genes are components of the P. aeruginosa core genome, several are located on presumptive horizontally acquired genomic islands. A comprehensive analysis of P. aeruginosa genes encoding the enzymes of c-di-GMP metabolism (DGC- and PDE-encoding genes) was carried out to analyze the function of c-di-GMP in two disease-related phenomena, cytotoxicity and biofilm formation. Analysis of the phenotypes of DGC and PDE mutants and overexpressing clones revealed that certain virulence-associated traits are controlled by multiple DGCs and PDEs through alterations in c-di-GMP levels. A set of mutants in selected DGC- and PDE-encoding genes exhibited attenuated virulence in a mouse infection model. Given that insertions in different DGC and PDE genes result in distinct phenotypes, it seems likely that the formation or degradation of c-di-GMP by these enzymes is in highly localized and intimately linked to particular targets of c-di-GMP action.

Pesquisa de fatores de virulência em Pseudomonas aeruginosa isoladas de águas minerais naturais

“…Determinados fatores ambientais, como luz, oxigênio e nutrientes, podem modular a expressão de c-diGMP (Kulasakara et al, 2006). De acordo com Yasuhiko et al (2012), o biofilme formado devido ao aumento de c-diGMP intracelular tende a ser mais aderente e robusto do que em cepas que produzem biofilme sem ativar esta via.…”

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…In contrast, increased attachment coinciding with pellicle formation was observed for potential DGC-PDE mutants (PA0861, PA3311, PA4367, and PA5017). Insertions in genes encoding only PDE domains, with the exception of pvrR, did not cause a biofilm-related phenotype under the conditions tested (86). Among the identified DGCs playing a role in attachment was WspR (PA3702).…”

“…While the majority of these were not found to have an effect on biofilm formation under static conditions during a mariner transposon mutant screen, insertions in a number of genes encoding DGCs reduced (PA1107, PA1181, PA1433, PA1727, and PA3702) or abolished (PA0169, PA1120, PA4959, and PA5487) attachment (86). In contrast, increased attachment coinciding with pellicle formation was observed for potential DGC-PDE mutants (PA0861, PA3311, PA4367, and PA5017).…”

“…SadC has been demonstrated to contribute to attachment. However, while inactivation of sadC by transposon mutagenesis in P. aeruginosa PA14 was shown to result in increased attachment and pellicle formation (86), deletion of sadC in the same parental strain rendered the mutant impaired in biofilm formation (104). It is likely that such inconsistencies arise from differences in parental strains or in the manner in which mutants were generated or from differences in growth conditions and experimental setup or that it may simply be a question of when over the course of the biofilm developmental process the biofilm formation capabilities were analyzed.…”

“…The genome of P. aeruginosa PAO1 encodes 17 different proteins with a DGC domain, 5 with a PDE domain, and 16 that contain both of these domains (86). While the majority of these were not found to have an effect on biofilm formation under static conditions during a mariner transposon mutant screen, insertions in a number of genes encoding DGCs reduced (PA1107, PA1181, PA1433, PA1727, and PA3702) or abolished (PA0169, PA1120, PA4959, and PA5487) attachment (86).…”