IMPACT OF PHYSIOLOGICAL-STATE ON SURFACE THERMODYNAMICS AND ADHESION OF PSEUDOMONAS-AERUGINOSA

A quantitative understanding of microorganism migration in geological formations is critical to predict the dissemination of microorganisms in the environment and to evaluate the efficacy of microbially mediate d in situ pollutant degradation. The key event that retards the moveme nt of microorganisms in the saturated zone with respect to the convect ive water flow is the interaction between microorganisms and the matri x surfaces. This interaction may result in adhesion and concomitant re tardation. Interactions are determined by the surface thermodynamics o f the microorganism and the matrix. Whereas the nature of the matrix s ubstratum surface may be considered temporally invariant, the nature o f bacterial cell surfaces is a function of its physiological state. Th e work presented here explored quantitatively the impact of the physio logical state of Pseudomonas aeruginosa Olin on its surface thermodyna mic characteristics and its adhesion to dolomite. Lewis acid/base (hyd rophobic), Lifshitz-van der Waals (electrodynamic), and Coulombic (ele ctrostatic) forces were measured via contact angle measurements and el ectrophoretic mobility assays. It was found that P. aeruginosa Olin ex hibited a decreased electron-donating potential (gamma(i)(-)) and incr eased zeta-potential in the stationary phase as compared with logarith mic growth and decay phases. These changes in surface thermodynamic pr operties were clearly manifested in subsequent partitioning experiment s with dolomite. P. aeruginosa Olin was found to partition onto dolomi te to a significantly larger extent in the stationary phase than in th e logarithmic growth or decay phases. This observation further corrobo rates the need to include Lewis acid/base interactions in the evaluati on of bacterium/surface interactions. The reported results indicate th e clear impact of physiological state on surface thermodynamics and ad hesion.