Studying the function of mitochondrial ING2, a tumor suppressor protein frequently lost in non-small cell lung cancer

PosterInternational audienc

Phenotypic variation in the Pseudomonas fluorescens clinical strain MFN1032

International audiencePseudomonas fluorescens is a highly heterogeneous species and includes both avirulent strains and clinical strains involved in nosocomial infections. We previously demonstrated that clinical strain MFN1032 has hemolytic activity involving phospholipase C (PlcC) and biosurfactants (BSs), similar to that of the opportunistic pathogen Pseudomonas aeruginosa. When incubated under specific conditions, MFN1032 forms translucent phenotypic variant colonies defective in hemolysis, but not necessarily in PlcC. We analyzed eight variants of the original strain MFN1032 and found that they clustered into two groups. Mutations of genes encoding the two-component regulatory system GacS/GacA are responsible for phenotypic variation in the first group of variants. These group 1 variants did not produce secondary metabolites and had impaired biofilm formation. The second group was composed of hyperflagellated cells with enhanced biofilm capacity: they did not produce BSs and were thus unable to swarm. Artificial reduction of the intracellular level of c-di-GMP restored the ability to form biofilm to levels shown by the wild type, but production of BSs was still repressed. Phenotypic variation might increase the virulence potential of this strain

Comparative study of 7 fluorescent pseudomonad clinical isolates.

International audienceThere is some debate about the potential survival of Pseudomonas fluorescens at temperatures above 37 degrees C and its consequences for infectious potential, owing to the heterogeneity of clinical strains. Seven clinical strains growing at 37 degrees C or more were submitted for polyphasic identification; 2 were identified as Pseudomonas mosselii and 4 were precisely characterized as P. fluorescens bv. I or II. The binding indexes on glial cells of the strains identified as P. fluorescens bv. I and P. mosselii were compared with that of a reference psychrotrophic strain, P. fluorescens MF37 (bv. V). Clinical P. fluorescens had a similar adherence potential range than strain MF37. Conversely, the binding indexes for P. mosselii strains were 3 times greater than that for strain MF37. These data, and those obtained by comparing the cytotoxic activities of P. fluorescens clinical strains, suggest the existence of different virulence mechanisms, leading either to a low infectious form or to a microorganism with cytotoxic activity in the same range as that of P. mosselii or even Pseudomonas aeruginosa