Multiple-metal tolerance in Pseudomonas fluorescens and its biotechnological significance

Abstract We have recently shown the tolerance of the soil microbe Pseudomonas fluorescens to a multiple-metal stress comprised of Al, Ca, Zn, Fe and Ga (Appanna, V.D. and St. Pierre, M. Cellular adaptation to a multiple-metal stress in Pseudomonas fluorescens . J. Biotechnol. 48, 129–136, 1996). Here we demonstrate the influence of Mn, Co, Cs and Ni on the ability of the microbe to adapt to and to decontaminate this multiple-metal environment. While both Cs and Mn did not appear to significantly alter the cellular yield, Co and Ni had a marked inhibitory influence on the microbial growth. The inclusion of Co in the multiple-metal medium led to a 41% decrease in biomass as observed at the stationary phase of growth. While in the presence of Ni, cellular multiplication was arrested. As bacterial growth progressed, the test metals were immobilized as an insoluble residue. Phosphatidylethanolamine (PE) appeared to be an important organic constituent of this deposit. Ultracentrifugation studies revealed that the nature of these metals was being modified from early stages of growth. There were no significant variations in exocellular carbohydrate or protein contents and in the pH of the control and metal-supplemented cultures. This model may have potential application in the remediation of metal pollutants.