Signalling pathway controlling cupD fimbrial genes expression and role in Pseudomonas aeruginosa pathogenesis
Lead Research Organisation:
Imperial College London
Department Name: Life Sciences
Abstract
Most microbes in nature exist as surface associated communities called biofilms. Biofilms are described as a 'city of microbes' in which bacteria are hold together into a solid matrix. There is compelling evidence that the biofilm lifestyle is an efficient means for microorganisms to maintain a protected niche. Establishment of biofilms in humans leads to chronic infection that can persist for life and lead to host death. It is well described that stability and resilience of biofilms is a major medical and industrial problem. Biofilms have been shown to display resistance to antibiotic treatments and are recalcitrant to eradication via the immune system. The formation of the biofilm obeys to a series of events that start with initial attachment of the bacterium on the host tissue. The initial attachment requires bacterial surface adhesins that are frequently associated with long fibres called fimbriae. In the course of the infection process, the bacteria should adapt and either form a biofilm to persist or colonize the host more aggressively. For bacteria, these choices are based in large part on local environmental cues, and are effected through altered gene expression. For example whether the bacteria decide to stop motility and start attachment may result in the assembly of these long fibres-containing adhesins. In order to detect the environmental cues bacteria have evolved regulatory devices that are made of two-components, one for signal detection and one for affecting gene expression, both components, called sensor and response regulator being intimately linked. The opportunistic pathogen Pseudomonas aeruginosa is a prototype of free-living organism with the capacity to cause disease in a wide range of eukaryotic hosts. P. aeruginosa is responsible for some of the most serious infections in humans, including emerging nosocomial infections associated with impairment of host defences. It is responsible for severe lung and upper respiratory tract infections in patients with Cystic Fibrosis and acute pneumopathies. P. aeruginosa is equipped with numerous genes responsible for the assembly of the above-mentioned fimbriae (cup genes). Moreover, this bacterium has a wide repertoire of two-component systems that give this organism an ubiquitous and versatile character. Finally, P. aeruginosa displays a remarkable range of virulence, from weakly virulent isolates to highly virulent broad-spectrum strains. In the present study we will investigate the role of a two-component regulatory system (Rcs/Pvr) on expression of cupD fimbrial genes. We have chosen to study those genes, because they are located on the pathogenicity island of the highly virulent P. aeruginosa PA14 strain. These genes are otherwise not found in the genome of the laboratory strain P. aeruginosa PAO1. Pathogenicity islands are of mobile genetic elements, which play a pivotal role in the virulence of bacterial pathogens of humans, animals and plants. Our study will bring original, detailed and integrated molecular basis about a complex network of regulation, the Pvr/Rcs system, and the specific cupD gene target. The characterization of the role of these systems in biofilm and virulence will improve our basic knowledge of signalling and fimbriae assembly in P. aeruginosa and will provide molecular details for the search of lead molecules interfering with P. aeruginosa pathogenesis.
Technical Summary
The versatile and ubiquitous bacterium Pseudomonas aeruginosa is the quintessential opportunistic pathogen, because it can infect a broad range of hosts, from amoeba to humans, where it is found associated with burns, cystic fibrosis (CF), AIDS, and cancer. This pathogen produces an arsenal of virulence factors, among which a large number of secreted hydrolytic enzymes and toxins that contribute to survival within the host and cytotoxicity. In addition, cell surface adhesive structures, such as pili, contribute to attachment onto the host tissues. Such attachment frequently results in biofilm formation and may lead to recurrent and chronic infection. Chaperone-usher pathways have been identified in P. aeruginosa and named Cup. They are responsible for the assembly of cell surface fibres named fimbriae. The cupD gene cluster, not existing in the laboratory strain PAO1, is located on the PAPI-1 pathogenicity island of the highly virulent PA14 strain. The cupD cluster is adjacent to genes encoding two component system regulatory proteins (Rcs/Pvr). Two component systems are regulatory devices that detect environmental signal and switch gene expression to allow bacteria to adapt to new environments. The Rcs/Pvr system is similar to the previously described Bvg system in Bordetella pertussis, the master regulator for expression of virulence genes. Whereas RcsB is a transcriptional activator, PvrR is a putative phosphodiesterase capable of c-di-GMP degradation. Our study will bring original, detailed and integrated molecular basis about a complex network of regulation, the Pvr/Rcs system, and the specific cupD gene target. This system should be considered as an archetype to understand the combined role of direct gene expression and c-di-GMP signalling in the process of P. aeruginosa biofilm formation and virulence. Our study will yield basic knowledge and provide molecular details for the search of molecules interfering with P. aeruginosa pathogenesis.
People |
ORCID iD |
Alain Filloux (Principal Investigator) |
Publications
Garnett JA
(2015)
Structure-function analysis reveals that the Pseudomonas aeruginosa Tps4 two-partner secretion system is involved in CupB5 translocation.
in Protein science : a publication of the Protein Society
Mikkelsen H
(2011)
The Pseudomonas aeruginosa reference strain PA14 displays increased virulence due to a mutation in ladS.
in PloS one
Mikkelsen H
(2011)
Key two-component regulatory systems that control biofilm formation in Pseudomonas aeruginosa.
in Environmental microbiology
Mikkelsen H
(2013)
The pathogenicity island encoded PvrSR/RcsCB regulatory network controls biofilm formation and dispersal in Pseudomonas aeruginosa PA14.
in Molecular microbiology
Moscoso JA
(2014)
The diguanylate cyclase SadC is a central player in Gac/Rsm-mediated biofilm formation in Pseudomonas aeruginosa.
in Journal of bacteriology
Moscoso JA
(2011)
The Pseudomonas aeruginosa sensor RetS switches type III and type VI secretion via c-di-GMP signalling.
in Environmental microbiology
Sivaneson M
(2011)
Two-component regulatory systems in Pseudomonas aeruginosa: an intricate network mediating fimbrial and efflux pump gene expression.
in Molecular microbiology
Description | 1. Demonstration that the PA14 Pseudomonas aeruginosa RcsB and PvrR response regulators antagonistically control fimbrial cupD genes (published in Mikkelsen et al., PLoS One, 2009). 2. Unexpected organisation of the Rcs/Pvr pathway. The PvrS sensor activates the RcsB regulator using RcsC as a phosphorelay. The rcs/pvr and cupD genes are located on a pathogenicity island. The RcsB regulon was tested using microarrays showing that cupD are not the only genes controlled. We identified three regulatory genes on the core genome that are up-regulated by RcsB and which possesses a RcsB binding site (Mikkelsen et al., Mol Microbiol. In preparation). 3. The Roc system homologous to the Rcs/Pvr system is located on the core genome. In the Pseudomonas PAK strain we showed that Roc, not only impact cupC gene expression and biofilm formation, but also impacts efflux pump expression and antibiotic resistance (published in Sivaneson, Mikkelsen et al., Mol. Microbiol., 2011). |
Exploitation Route | Drug targets for pharmaceutical companies. Understanding the regulatory networks associated with bacterial biofilm and chronic infections is one way to develop new drugs interfering and subverting the bacterial infection strategy and to provide new therapeutic routes. |
Sectors | Education Pharmaceuticals and Medical Biotechnology |
Description | Collaboration on Pseudomonas CupA fimbriae - Tanmay Bharat - Oxford University |
Organisation | University of Oxford |
Department | Sir William Dunn School of Pathology |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Providing Pseudomonas aeruginosa strains overexpressing or lacking cupA fimbriae |
Collaborator Contribution | Tanmay Bharat group will look at the presence of fimbria at the bacterial surface and will atempt purification and structural analysis using cryo-EM |
Impact | None |
Start Year | 2017 |
Description | Imperial Festival - Super Bugs Zone - 27-29 April 2018 |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | Open Day odf the CMBI at the annula Impetrial Festival. Several stands at the Supoer Bugs Zone describing multiple aspects of bacterial pathogens. |
Year(s) Of Engagement Activity | 2018 |
Description | The Pseudomonas aeruginosa Rcs and Pvr two-component systems are novel players in the switch between planktonic and sessile lifestyles, ASM Cancun, 2009, Poster Mikkelsen |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Type Of Presentation | poster presentation |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Poster presentation at the ASM Biofilm meeting in Cancun (Mexico) on 14-20 November 2009. Presenter Helga Mikkelsen no actual impacts realised to date |
Year(s) Of Engagement Activity | 2009 |
Description | The Rcs and Pvr two-component systems are novel players in the switch between the planktonic and sessile lifestyles of Pseudomonas aeruginosa, Winchester 2010, Poster Mikkelsen |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Type Of Presentation | poster presentation |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Poster presentation at the Biofilm 4 conference in Winchester (UK) on 1-3 September 2010. Presenter Helga Mikkelsen no actual impacts realised to date |
Year(s) Of Engagement Activity | 2010 |
Description | The RcsB response regulator is central to a network controlling attachment in P. aeruginosa PA14, Pseudomonas 2011, Sydney, Poster Mikkelsen |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Type Of Presentation | keynote/invited speaker |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Invited talk at the ASM conference on Pseudomonas in Sydney on September 4-7, 2011. Presenter Helga Mikkelsen no actual impacts realised to date |
Year(s) Of Engagement Activity | 2011 |