The variation of Cu2+ adsorption capacity of Pseudomonas putida 5-x cell envelope with cell age was studied. Results showed that cell surface components in the cell envelope, such as the peptidoglycan layer, outer and inner membranes, all contributed to the Cu2+ adsorption by P. putida 5-x cell envelope. The content of the peptidoglycan layer, and the outer and inner membranes in the cell envelope varied, while the Cu2+ adsorption capacities of separated outer and inner membranes varied in different growth phases. But the adsorption capacity of separated PEG layer remained constant in all growth phases. The variation of adsorption capacity of the cell envelope with cell age is mainly due to the variation of the contents of the peptidoglycan layer, and the outer and inner membranes in the cell envelope, as well as the variation of adsorption capacities of the outer and inner membranes in different cell ages. In addition, the variation of both phospholipid and lipopolysaccharide content in the outer membrane, and phospholipid content in the inner membrane with cell age resulted in the variation of adsorption capacities of the outer and inner membranes in different cell ages. (C) 2004 Elsevier Inc. All rights reserved.