Influence of growth temperature on cyclopeptides production and on adhesion behaviour in environmental strains of Pseudomonas fluorescens
Résumé
The present study deals with the influence of growth temperature on biosurfactant production and the adhesion process in the psychrotrophic species Pseudomonas fluorescens. We studied a strain panel composed of nine wild cyclolipopeptide (CLPs) producers and by two biosurfactant mutants. Where cyclolipopeptide production was characterized at either 8°C or 17°C, cyclolipopeptide production was highlighted by hemolytic and tensiometric methods. Their ionic charge was evaluated by a double diffusion test and their identification was made as amphisin- or viscosin- or viscosinamide-like biosurfactants by Reverse Phase- High Performance Liquid Chromatography- Mass Spectroscopy.
This categorization was corroborated by the 16S rRNA phylogenetic study. In Pseudomonas fluorescens, the number and relative quantity of cyclolipopeptide produced and bacterial adhesion differed with the growth temperature. Seven new cyclolipopeptides were characterized, of which three belong to the viscosinamide family. Biosurfactant secretion is intensive at 17°C and the highest adhesion is obtained at a lower temperature (8°C). Cyclolipopeptides appeared to antagonize the adhesion process. Strain hydrophobicity was wholly independent of growth temperature and could not be correlated with the initial attachment of bacteria, which was thermoregulated. Our study demonstrates that bacterial
adhesion is controlled by the growth temperature but not by cyclolipopeptides or cell hydrophobicity.