Abstract
Toluene tolerant bacterium G11 was isolated from sludge and identified as Bacillus thuingiensis. B. thuringiensis G11 could grow in the presence of a separated phase of organic solvents, having value of logPo/w from 1 to 4. In order to clarify the mechanism of organic solvent tolerance at the whole cell level, accumulation of toluene in cell biomass and cell surface property were investigated. The accumulation rate of toluene in cell biomass of G11 strain was much lower than that of non-tolerant bacteria, suggesting the presence of efflux pump of organic solvents. The cell surface property was evaluated by microbial adhesion to hydrocarbons (MATH) method. The adhesion of the cell to n-hexadecane was carried out for evaluating hydrophobicity of the cell surface. As the results, for B. thuringiensis G11, adhesion of adapted cell of G11 strain to toluene was much lower than that of non-adapted cell of G11 strain. This behavior was not observed for non-tolerant bacteria. From these facts, organic solvents tolerance of B. thuringiensis G11 is likely caused by not only the efflux systems but also change in cell surface property.
