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首页> 外文期刊>Environmental toxicology and chemistry >Effect Of Competing Ions And Complexing Organic Substances On The Cadmium Uptake By The Soil Bacterium Sinorhizobium Meliloti
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Effect Of Competing Ions And Complexing Organic Substances On The Cadmium Uptake By The Soil Bacterium Sinorhizobium Meliloti

机译：竞争离子和络合有机物对土壤微生物中华根瘤菌吸收镉的影响

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In an effort to improve the understanding and prediction of Cd uptake by soil bacteria, adsorbed and intracellular Cd were determined in unpolluted and highly polluted model soil solutions within a concentration range spanning from 10~(-9) to 5 × 10~(-5) M Cd. In parallel, the free Cd ion concentrations ([Cd~(2+)]) were measured by a hollow fiber permeation liquid membrane. Obtained results demonstrated that Cd uptake by bacterium Sinorhizobium meliloti was related to [Cd~(2+)] in the solution. Addition of different complexing organic substances reduced [Cd~(2+)] in the bacterial medium and decreased both adsorbed and intracellular Cd. The adsorbed Cd was considerably reduced in the presence of 10~(-4) to 5 × 10~(-2) M [Ca] or [Mg]. No effect on Cd adsorption was observed in the presence of Zn or Mn, even at 100-fold excess. Intracellular Cd decreased in the presence of a high excess of Ca and Zn, while no significant effect was observed in the presence of Mg. An increase of dissolved Mn from 10~(-9) to 10~(-8) M resulted in a twofold decrease of the intracellular Cd, but no clear trend was observed in the presence of 10~(-7) to 10~(-6) M Mn. Based on complexation and competition studies, the stability constants, necessary for quantitative description of Cd uptake by S. meliloti and the development of the bacterial biotic ligand model for Cd, were derived and validated in the solutions containing mixtures of Cd, Zn, Ca, and Mg. Further numerical simulations of Cd uptake by S. meliloti exposed to soil pore waters demonstrated the importance of Zn competition and the insignificant influence of Ca and H on Cd uptake.
机译：为了更好地理解和预测土壤细菌对Cd的吸收，在浓度范围为10〜（-9）至5×10〜（-5）的无污染和高污染的模型土壤溶液中测定了吸附和细胞内Cd的含量。 ）Cd。平行地，通过中空纤维渗透液膜测量游离Cd离子浓度（[Cd〜（2+）]）。所得结果表明，苜蓿中华根瘤菌对镉的吸收与溶液中的[Cd〜（2+）]有关。不同络合有机物的添加减少了细菌培养基中的[Cd〜（2+）]，同时降低了吸附和胞内Cd。在10〜（-4）M [Ca]或[Mg]存在下，吸附的Cd显着降低。在锌或锰的存在下，即使过量100倍，对镉的吸附也没有影响。在大量过量的钙和锌的存在下，细胞内镉下降，而在镁的存在下，未观察到明显的影响。 Mn从10〜（-9）增加到10〜（-8）M导致细胞内Cd减少两倍，但是在10〜（-7）到10〜（ -6）M锰。在复杂化和竞争研究的基础上，得出了稳定性常数，该常数对于描述苜蓿链球菌对Cd的吸收和建立Cd的细菌生物配体模型是必需的，并在包含Cd，Zn，Ca，和镁。暴露于土壤孔隙水的苜蓿链球菌对Cd吸收的进一步数值模拟证明了Zn竞争的重要性以及Ca和H对Cd吸收的微不足道的影响。

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