Final Report Summary - PSEUDOTOX (Integration of regulatory networks in Pseudomonas)
In the Intra-European Fellowships (IEF) project PSEUDOTOX, internationally known research experts investigated regulatory networks and chemical biology of the bacterium Pseudomonas aeruginosa with the goal to identify new antibacterial targets. P. aeruginosa is a bacterium pathogenic to humans, accounting for 10 % of hospital-acquired infections. It plays a major role in colonising lungs of patients with the recessive genetic condition cystic fibrosis. Traditional antibiotic therapy for patients with P. aeruginosa infections is extremely difficult because of its high antibiotic resistance. This organism produces a whole armoury of virulence determinants which are responsible for it success in disease processes. These are controlled by wide range of switches. Amongst the key ones are:
(i) the post- transcriptional regulatory system rsm;
(ii) the intercellular signalling mechanism quorum sensing (QS) and
(iii) the intracellular signalling system mediated by the global secondary messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP).
Together these systems control the virulence and lifestyle of P. aeruginosa during infection. QS, the rsm system and c-di-GMP signalling are widespread in many bacterial pathogens. Consequently, they have a unique potential for the development of novel antimicrobial agents capable of controlling infection through their blockade.
QS controls interactions between a wide spectrum of pathogenic and beneficial bacteria and higher organisms in the context of pathogenicity, symbiosis and growth promotion. Consequently, QS has major impacts on medicine, industry, agriculture and ecology where QS systems control the adaptive behaviour of microbes during the colonisation and infection of animal hosts, in the context of plant-microbe interactions (pathogenicity / plant growth promotion and biocontrol), food spoilage and marine and industrial plant biofouling.
The c-di-GMP intracellular signalling systems have also been found to be wide spread in bacteria and play a key role in the formation of biofilms of bacterial slime cities as well as determining the transition between sessility and motility in bacterial populations.
The rsm system has been shown to have a key role in modulating the production of virulence determinants, secondary metabolites and biofilm formation at the posttranscriptional level, i.e. the cellular process that goes between the activation of a virulence gene and the production of the virulence factor it codes for. The host research group had previously shown that there is a close relationship between the rsm system and QS.
A major virulence factor produced by P. aeruginosa is exotoxin A, which inhibits protein synthesis in susceptible host cells resulting in their killing. Exotoxin A expression is known to be regulated by a gene called toxR (toxin regulatory gene). Although for a long time it has been believed that the role of ToxR was merely to control the production of Exotoxin A, we have discovered that this gene modulates the activation of a wide range of genes in P. aeruginosa by comparing the gene expression profiles in a toxR mutant and its wild-type counterpart. Furthermore, using sophisticated molecular biology and biochemistry technologies, as well as the performance of numerous virulence and phenotypic assays, we have discovered that ToxR forms part the above regulatory networks in P. aeruginosa.
In summary, this IEF project has discovered that ToxR is an important factor in the regulation of the virulence of P. aeruginosa and that this regulation takes place through its integration into more complex regulatory pathways. The discovery of these new interactions will without doubt form the basis for the identification novel targets within these pathways for the development of novel antimicrobials against this important opportunistic pathogen.
Target groups:
The outcomes from this project will be of interest to pharmaceutical industry, academic and research institutions.
(i) the post- transcriptional regulatory system rsm;
(ii) the intercellular signalling mechanism quorum sensing (QS) and
(iii) the intracellular signalling system mediated by the global secondary messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP).
Together these systems control the virulence and lifestyle of P. aeruginosa during infection. QS, the rsm system and c-di-GMP signalling are widespread in many bacterial pathogens. Consequently, they have a unique potential for the development of novel antimicrobial agents capable of controlling infection through their blockade.
QS controls interactions between a wide spectrum of pathogenic and beneficial bacteria and higher organisms in the context of pathogenicity, symbiosis and growth promotion. Consequently, QS has major impacts on medicine, industry, agriculture and ecology where QS systems control the adaptive behaviour of microbes during the colonisation and infection of animal hosts, in the context of plant-microbe interactions (pathogenicity / plant growth promotion and biocontrol), food spoilage and marine and industrial plant biofouling.
The c-di-GMP intracellular signalling systems have also been found to be wide spread in bacteria and play a key role in the formation of biofilms of bacterial slime cities as well as determining the transition between sessility and motility in bacterial populations.
The rsm system has been shown to have a key role in modulating the production of virulence determinants, secondary metabolites and biofilm formation at the posttranscriptional level, i.e. the cellular process that goes between the activation of a virulence gene and the production of the virulence factor it codes for. The host research group had previously shown that there is a close relationship between the rsm system and QS.
A major virulence factor produced by P. aeruginosa is exotoxin A, which inhibits protein synthesis in susceptible host cells resulting in their killing. Exotoxin A expression is known to be regulated by a gene called toxR (toxin regulatory gene). Although for a long time it has been believed that the role of ToxR was merely to control the production of Exotoxin A, we have discovered that this gene modulates the activation of a wide range of genes in P. aeruginosa by comparing the gene expression profiles in a toxR mutant and its wild-type counterpart. Furthermore, using sophisticated molecular biology and biochemistry technologies, as well as the performance of numerous virulence and phenotypic assays, we have discovered that ToxR forms part the above regulatory networks in P. aeruginosa.
In summary, this IEF project has discovered that ToxR is an important factor in the regulation of the virulence of P. aeruginosa and that this regulation takes place through its integration into more complex regulatory pathways. The discovery of these new interactions will without doubt form the basis for the identification novel targets within these pathways for the development of novel antimicrobials against this important opportunistic pathogen.
Target groups:
The outcomes from this project will be of interest to pharmaceutical industry, academic and research institutions.