Study of marine bacteria adhesion on sea-immersed 304 and 316 stainless steels: experimental and theoretical investigations

In this study, we investigated the potential adhesion of marine bacteria isolated from seawater in the port of Chmaâla, Morocco, to sea-immersed 304 and 316 stainless steels using thermodynamic approach and the Environmental Scanning Electron Microscopy (ESEM). Furthermore, the physicochemical properties including hydrophobicity and electron donor / electron acceptor (Lewis acid-base) of bacterial isolates and both substrates were evaluated using the contact angle measurements. The molecular identification indicated that the isolated strains were Bacillus thuringiensis and Bacillus amyloliquefascience. Results also showed that both bacterial strains’s cells have a hydrophilic character with ΔGiwi values of 29.30 and 24.12 mJ m−2 respectively for Bacillus thuringiensis and Bacillus amyloliquefascience, and are strong electron donating (γ−) and weakly electron accepting (γ+). For substrates surfaces, we found that both sea-immersed stainless steels types were hydrophilic and present strong electron-donor character (γ− = 49 ± 0.2 mJ m−2 for 304 and γ− = 55.07 ± 0.02 mJ m−2 for 316) and weak electron-acceptor character (γ+ = 5.4 ± 0.1 mJ m−2 for 304 and γ+ = 8.3 ± 0.06 mJ m−2 for 316). The theoretical prediction showed that both tested strains, B. thuringiensis and B. amyloliquefascience, exhibited positive values of ΔGTotal vis-à-vis the two sea-immersed stainless steels types which indicates unfavorable adhesion while the ESEM electro-micrographs show that both strains were able to adhere to both strainless steels surfaces.