Evaluation of the cytotoxicity and interaction of lead with lead resistant bacterium Acinetobacter junii Pb1

This study explores the potential of lead resistant bacterium Acinetobacter junii Pb1 for adsorption/accumulation of lead using various techniques. In the present work, growth of A. junii Pb1 was investigated in the presence of a range of Pb(II) concentrations (0, 100, 250, 500, and 1000 mg l^-1). Lead was found to have no toxic effect on the growth of A. junii Pb1 at 100 and 250 mg l^-1 concentrations. However, further increase in Pb(II) concentration (500 mg l^-1) showed increase in lag phase, though growth remained unaffected and significant growth inhibition was observed when concentration was increased to 1000 mg l^-1. Same was confirmed by the observations of flow cytometry. Further, the effect of Pb(II) on A. junii Pb1 was evaluated by using fluorescence microscopy, spectrofluorimetry, and flow cytometry. The spectrofluorimetry and fluorescence microscopy results revealed the accumulation of Pb(II) inside the bacterial cells as evident by green fluorescence due to lead binding fluorescent probe, Leadmium Green AM dye. Flow cytometry observations indicate an increase in cell size and granularity of exposure to lead. Thus, present work provides a new understanding of Pb(II) tolerance in A. junii Pb1 and its potential use in remediation of lead from contaminated soil.