Compréhension des mécanismes d'adhésion des biofilms en milieu marin en vue de la conception de nouveaux moyens de prévention

Biofilm formation on surfaces immersed in sea water induces equipment damages. Recently, studies focused on the environmental impact of antifouling paints have shown that some active chemical compounds are harmful to the aquatic environment. Hence, it appears fundamental to study physico-chemical interactions existing between marine bacteria and various substrata to conceive new ecological products or antifouling processes. First, we model an artificial primary organic film, formed by the adsorption of BSA and polysaccharide, as close as the one formed in natural seawater. This organic film is heterogeneous (only 42% of the surface is covered) and organic adsorption occurs in a multi-layer scheme, molecules bounded each others by calcium and magnesium ions. Second, three marine bacteria, Vibrio splendidus (98,8% of RNA/RNA homology), Pseudomonas sp. and Pseudoalteromonas macleodii subsp. fijiensis, are characterised by analytical surface techniques. The combination of the results obtained by XPS and MATS shows that bacterial acido-basic properties can be explained by differences in surface compositions : highly hydrophilic bacteria exhibit polysaccharides whereas slightly hydrophilic bacteria exhibit proteins on their surfaces. Finally, bacterial adhesion on glass, stainless steel AISI 316L and PTFE samples which are or are not covered with an organic film points out that, in our laboratory conditions, primary organic film formation and bacterial adhesion may occur at the same time. Next, we show that kinetics of adhesion can be explained by bacterial surface composition and that polymers excreted by bacteria allow them to firmly attach to surfaces. Then, XPS and microbiological results lead us to say that bacteria don't only attach to the primary organic film.