Microbial surface thermodynamics and interactions in aqueous media were investigated for seven typical rod-shaped bacterial strains of Enterobacteriaceae, Pseudomonadaceas, and Bacillaceae, which included Echerichia coli HB101, Echerichia coli JM109, Pseudomonas fluorescens, Pseudomonas putida, Pseudomonas aeruginosa, Pseudomonas sp., and Bacillus subtilis. All the microorganisms studied exhibited a monopolar and predominant hydrophilic surface and a negative DeltaG(132)(tot), total free energy of interactions between microbes (1) and silica gel or Canadian River Alluvium (CRA) (2) immersed in water (3) at the equilibrium distance, which accounted for their attachment on the medium surface. The microbial attachment was proportional to the corresponding DeltaG(132)(tot) values. Among the microorganisms studied, B. subtilis had the most attachment on both silica gel and CRA because it had the smallest DeltaG(132)(tot) values (-17.14kT for silica gel and -21.84kT for CRA). The origins of Lifshitz-van der Waals, Lewis acid/base, and electrostatic interactions were discussed and related to experimental observations. (C) 2003 Elsevier Science (USA). All rights reserved.