Silver accumulation and resistance in Pseudomonas stutzeri

Silver (Ag) resistance and accumulation were investigated in Ag-resistant Pseudomonas stutzeri strain AG259 and Ag-sensitive P. stutzeri strain JM303. Both strains exhibited a similar pattern of silver accumulation although to different final concentrations. Energy-dispersive X-ray analyses revealed the association of dense silver deposits with the Ag-resistant strain, but not the Ag-sensitive strain. Toluene permeabilization or incubation of cells at 2°C resulted in decreased Ag accumulation in both strains. This suggests that Ag accumulation may be energy dependent. A decrease in Ag accumulation was observed when cells were pretreated with 2,4-dinitrophenol (2,4-DNP). No decrease was observed using carbonyl cyanide m-chlorphenyl-hydrazone (CCCP). However, it was observed that both 2,4-DNP and CCCP complexed to Ag, making interpretation of accumulation results difficult. Washing of cells incubated in the presence of Ag with ethylenediaminetetraacetic acid (EDTA) or hydrochloric acid did not result in decreased Ag accumulation.