Contribution of cell-surface components to Cu2+ adsorption by Pseudomonas putida 5-x

The contribution of various cell-surface components to Cu2+ adsorption by a Gram-negative bacterium, Pseudomonas putida 5-x, that was isolated from local electroplating effluent with a high capability to accumulate heavy metal ions was studied. The cell superficial layer had a negative effect on Cu2+ adsorption of the bacterial cells. Cu2+ adsorption capacity of the separated cell envelopes was fivefold more than that of the intact cells, owing to the liberation of more and more binding sites during the separation process. Some main components in the cell envelope, such as the peptidoglycan (PEG) layer, outer membrane, and inner membrane, provide the capability for Cu2+ adsorption. The content of the components in the cell envelope is in the order inner membrane > outer membrane > PEG layer, and their Cu2+ adsorption capacity was in the order PEG layer > outer membrane > inner membrane. The total contribution of the separated PEG layer material to Cu2+ adsorption by the cell envelope was no more than 15%, and the outer membrane and inner membrane contributed about 30-35% and 25-30%, respectively. The relatively high phospholipid content in the outer membrane may be the major reason for the higher adsorption capacity of the outer membrane to Cu2+ and, hence, such a high Cu2+ adsorption capacity of P. putida 5-x cell envelope.