Bacillus cereus adhesion: an investigation of the physicochemical characteristics of surface and effect of bio adhesion on the properties of silicone

The initial microorganism adhesion on substrate is an important step for biofilm formation. The surface properties of the silicone and Bacillus cereus were characterized by the sessile drop technique. Moreover, the physicochemical properties (hydrophobicity; electron donor/electron acceptor) of surface adhesion and the impact of bio adhesion on the silicone were determined at different time of contact (3, 7, and 24h). The results showed that the strain was hydrophilic (Giwi=3.37mJ/m2), whereas the silicone has hydrophobic character (Giwi=68.28mJ/m2). Silicone surface presents a weak electron-donor character ( =2.2mJ/m2) conversely to B. cereus that presents an important electron donor-parameter ( =31.6mJ/m2). The adhesion of B. cereus to silicone was investigated using environmental scanning electron microscope and image analysis was assessed with the Matlab (R) program. After 3h of contact, the data analysis, confirmed the bio adhesion with an amount of 9.6105cfu/cm2 adhered cells. After 24h, the percentage of silicone covered reached 93%. Furthermore, despite the difference in hydrophohbicity, the interaction between B. cereus and substrata was favoured by the thermodynamic model of adhesion (G adhesion <0). The real time investigation of the effect of B. cereus adhesion on the physicochemical properties of silicone has revealed that the substrata becomes hydrophilic (degrees=47.3, Giwi=23.7mJ/m2), after 7h of contact. This bio adhesion had also favoured the increase of electron donor/acceptor character of silicone ( =53.1mJ/m2 and +=5.3mJ/m2).