Surfactin and iturin A effects on Bacillus subtilis surface hydrophobicity

The synthesis of extracellular molecules such as biosurfactants should have major consequences on bacterial adhesion. These molecules may be adsorbed on surfaces and modify their hydrophobicities. Certain strains of Bacillus subtilis synthesize the lipopeptides, which exhibit antibiotic and surface active properties. In this study the high-performance liquid chromatography (HPLC) analysis of the culture supernatants of the seven B. subtilis strai ns, showed that the lipopeptide profile varied greatly according to the str ain. Among the three lipopeptide types, only iturin A was produced by all B . subtilis strains. Bacterial hydrophobicity, evaluated by the water contac t angle measurements and the hydrophobic interaction chromatography, varied according to the strain. Two strains (ATCC 15476 and ATCC 15811) showing e xtreme behaviors in term of hydrophobicity were selected to study surfactin and iturin A effects on bacterial hydrophobicity. The two lipopeptides mod ified the B. subtilis surface hydrophobicity. Their effects varied accordin g to the bacterial surface hydrophobic character, the lipopeptide type and the concentration. Lipopeptide adsorption increased the hydrophobicity of t he hydrophilic strain but decreased that of the hydrophobic. Comparison of lipopeptide effects on B. subtilis surface hydrophobicity showed that surfa ctin was more effective than iturin A for the two strains tested. (C) 2000 Elsevier Science Inc. All rights reserved.