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.