Growth temperature and OprF porin affect cell surface physicochemical properties and adhesive capacities of Pseudomonas fluorescens MF37.

Pseudomonads adapt to various ecological niches by forming biofilms, which first requires bacterial adhesion on surfaces. We studied the influence of growth temperature on surface physicochemical properties of Pseudomonas fluorescens MF37 and on its adhesive capacities onto inert surfaces. It presented a global hydrophilic character, measured by microbial adhesion to solvent (MATS), and showed a cell surface more hydrophilic at 8 and 28 degrees C than at 17 degrees C. Moreover, P. fluorescens MF37 was more adhesive at 17 degrees C. This critical temperature thus should be carefully taken into account in food safety. Adhesion onto inert surfaces is thus influenced by the growth temperature, which modifies the bacteria cell wall properties through changes in the outer membrane components. Therefore, we studied the effect of the loss of OprF, the major outer membrane protein, known to act as an adhesin (root, and endothelial cells). The OprF-deficient mutant was able to adhere to surfaces, but showed the same physicochemical and adhesion properties on abiotic surfaces whatever the growth temperature. OprF is thus not essential in this adhesion process. However, we suggest that OprF is involved in the bacterial environmental temperature sensing by P. fluorescens.