Cell surface properties of rhizobial strains isolated from soils contaminated with hydrocarbons: hydrophobicity and adhesion to sandy soil

Ten strains of Rhizobium meliloti and two non-rhizobial strains, Escherichi a coli JM105 and Comamonas testosteroni B-356, were studied for their behav iour in soil and water matrices by determining their hydrophobicity, as mea sured by bacterial adherence to n-octane, and adhesion, as measured by thei r retention on sandy soil particles. The hydrophobicity values for the rhiz obial strains were similar to that for E. coli (around 15%). whereas C. tes tosteroni, which belongs to the Pseudomonads group, showed a significantly higher level (33%). Both non-rhizobial strains, however, showed higher leve ls of adhesion, (85% and 78%, respectively) than did the rhizobial strains ( approximate to 55%). The cell surface properties of the rhizobial strains were influenced by the composition of the growth media used, being signifi cantly higher with nutrient-rich media. The nature or level of contaminants in the soil from which these strains were originally isolated did not, how ever, influence these properties. These characteristics are important in de termining the fate of bacteria in the unsaturated subsurface soil environme nt because of their influence on the vertical transport, distribution and s urvival. Information about these characteristics will be particularly usefu l in choosing strains for agricultural applications (e.g., as biofertilizer s or biocontrol agents) or in situ soil environmental operations (e.g., bio augmentation for bioremediation of pollutants). (C) 2001 Elsevier Science L td. All rights reserved.