In this study, we investigate the interaction of Rhodopseudomonas Palustris (R. Palustris) with montmorillonite clay. The adsorption of bacteria on the clay surface was also determined as a function of the initial bacterial quantity, pH, temperature and ionic strength. At different initial bacterial quantities, the percentage of bacteria adsorbed ranged from 61.07% to 77.57%, and the higher percentage was determined to be 15.0×108 cfu ml-1. In addition, the actual number of adsorbed cells was significantly correlated with the initial quantity of R. Palustris. A greater degree of R. Palustris adsorption on the montmorillonite was observed in the temperature range of 30oC to 40oC. It was also found that as the pH and ionic strength increased the percentage of bacterial adsorption on montmorillonite decreased. There were no significant differences (P > 0.05) in the enzyme activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) between the bacteria treated with and without montmorillonite. However, montmorillonite supplementation significantly increased (P < 0.05) the cell surface hydrophobicity of R. Palustris compared with the control. These results indicated that the interaction was controlled by physicochemical characteristics between cells and the mineral substrate