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Sensing environment & community lifestyle in Pseudomonas aeruginosa

Laboratoire d'Ingénierie des Systèmes Macromoléculaires - Team C.Bordi

Research interests

Pseudomonas aeruginosa is an opportunist gram-negative, pathogenic bacterium, endowed with a very big capacity of adaptation because it can colonize very numerous ecological niches, among which the ground, the aquatic environments, the plants, the animals and the man. Practically harmless at the healthy individual, this bacillus, exhibits indeed a formidable capacity to cause severe infections in immunodeficient subjects, such as those hospitalized in intensive care units and under ventilated-assistance (it occupies the 3rd rank of bacteria responsible for hospital-borne infections) or those suffering from chronic infections as the cystic fibrosis. 90 % of the microbiological activity in an ecosystem (aquatic environment, ground, human body) results largely from a sedentary flora adhering (subscribing) to surfaces in a structure of biofilm, this one being defined as an aggregate of microorganisms (mainly bacteria), fixed to a surface, and stuck in a gangue of autoproduced exopolymers. The presence of biofilms is more and more often identified as the recurring source of problems for public health, industrial and societal applications often heavy of consequences and sometimes dramatic. The passage of the planktonic life (associated with the secretion of effectors of type III, T3SS, for example) in the sedentary life (in the form of biofilms, associated with the secretion of type VI, T6SS) is under the control of a complex network of regulation involving in particular the two component systems or sigma factors. The TCS contain in their simplest shape two proteins; a sensor named histidine kinase which detects one or several environmental signals and a response regulator which is in the majority of the cases a transcriptional regulator. These pathways involving TCS can be connected or interconnected and bring in several sensors converging on the same regulator or several TCS acting on the same targets but via a cross-talk.
The team " Sensing environment & community lifestyle " studies the molecular aspects driving to the sedentary life as well as the phosphorelais or the alternative sigma factors involved in the transition between planktonic and sedentary lifestyle in P. aeruginosa and the interconnections between these various regulation systems during the infectious process. The recent researches realized in the group allowed on one hand 1/ to identify and to characterize the fimbriae of the chaperon-usher pathway, the conjugative or not conjugative type IVb pili, the adhesins or substrates of the machineries of secretion of type I (T1SS, BapA) and of type V (T5SS, Tps2) and on the other hand 2/ to characterize regulatory pathways involving the TCS PprAB, the sensor LadS together with the TCS GacSA, the system HptB/HsbR/HsbA, the TCS Roc2, the alternative sigma factor VreI.

The group is integrated and active in the GDR Pseudomonas (GDR 3171) and implements approaches of genetics and molecular biology, of microscopy and genomics (sequencing and annotation of new genomes, microarrays, random mutagenesis, pan-interactome) and collaborates for aspects implying biochemistry and structural biology (Team Francoise Guerlesquin (MNR), LISM Marseille and Team Yves Bourne (X-ray crystallography), AFMB, Marseille) and the virulence (Team Ina Attrée, CEA Grenoble and Team Patrick Plésiat, EA Besançon).