Successful application of microorganisms to heavy metal remediation depends on their resistance to toxic metals. This study contrasted the differences of tolerant mechanisms between Pb²⁺ and Cd²⁺ in Enterobacter sp. Microbial respiration and production of formic acid showed that Enterobacter sp. had a higher tolerant concentration of Pb (>1000 mg l⁻¹) than Cd (about 200 mg l⁻¹). Additionally, SEM confirmed that most of Pb and Cd nanoparticles (NPs) were adsorbed onto cell membrane. The Cd stress, even at low concentration (50 mg l⁻¹), significantly enlarged the sizes of cells. The cellular size raised from 0.4 × 1.0 to 0.9 × 1.6 μm on average, inducing a platelet‐like shape. In contrast, Pb cations did not stimulate such enlargement even up to 1000 mg l⁻¹. Moreover, Cd NPs were adsorbed homogeneously by almost all the bacterial cells under TEM. However, only a few cells work as ‘hot spots’ on the sorption of Pb NPs. The heterogeneous sorption might result from a ‘self‐sacrifice’ mechanism, i.e., some cells at a special life stage contributed mostly to Pb sorption. This mechanism, together with the lower mobility of Pb cations, caused higher microbial tolerance and removal efficiency towards Pb²⁺. This study sheds evident contrasts of bacterial resistance to the two most common heavy metals.

中文翻译：

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对比肠杆菌的Pb（II）和Cd（II）耐受性。通过其细胞应激反应

微生物在重金属修复中的成功应用取决于它们对有毒金属的抵抗力。这项研究对比的容错机制铅之间的差别²⁺和Cd ²⁺的肠杆菌属。微生物的呼吸作用和甲酸的产生表明肠杆菌属。铅的耐受浓度（> 1000 mg l ^-1）高于镉（约200 mg l ^-1）。此外，SEM证实大多数Pb和Cd纳米颗粒（NPs）都吸附在细胞膜上。即使在低浓度（50 mg l ^-1），大大扩大了细胞的大小。细胞大小平均从0.4×1.0增加到0.9×1.6μm，形成血小板样形状。相反，Pb阳离子甚至在高达1000 mg l ^-1时也不会刺激这种增大。而且，Cd NPs在TEM下几乎被所有细菌细胞均一地吸附。但是，只有少数细胞充当Pb NPs吸附的“热点”。异质吸附可能是由于“自我牺牲”机制引起的，即某些处于特殊生命阶段的细胞主要是对Pb吸附的贡献。这种机制，加上较低的Pb阳离子迁移率，导致较高的微生物耐受性和对Pb ^2+的去除效率。这项研究揭示了细菌对两种最常见的重金属的抵抗力的明显对比。