Effects of environmental factors on uptake and accumulation of ore-forming elements by bacteria

Abstract

The effects of environmental factors, such as pH, sodium and calcium on the uptake and accumulation of ore-forming element cesium by bacteria were studied under K+-sufficient and K+-deficient culturing conditions in terms of quantity of uptake and accumulation (QUA), respectively. The mechanism of the uptake and accumulation and kinetics of the high-affinity Cs+ in K+-deficient cells were also studied. Culturing conditions with and without K+ played a significant role in the uptake and accumulation of cesium. The QUA of cesium was much higher in K+-deficient cells than that in K+-sufficient cells. The uptake and accumulation of cesium were subjected to external H+, Na+ and Ca2+: The QUA decreased at both higher (9.0) and lower (3.0) pH values in K+-deficient cells, whereas the K+-sufficient cells experienced less differences at various pH values, though the highest QUA remained at pH 7.5 the same as in the K+-deficient cells. Na+ showed greater inhibition to the uptake and accumulation of cesium at higher concentration in both K+ regimes but less so in K+-sufficient cells (30%) than in K+-deficient cells (45%). Ca2+, however, revealed much more complicated effects. Bacteria showed the highest capacity of uptake and accumulation at Ca2+concentration of 700 µmol/L, 10 times higher than that of Cs+, in K+-deficient cells. However, in K+-sufficient cells, the higher QUA appeared at Ca2+ concentrations of 70 and 7 µmol/L, with a little higher at 7 µmol/L.