List of bacterial strains and plasmids used.

Zinc is an essential metal for cells, but excess amounts are toxic. Other than by regulating the intracellular zinc concentration by zinc uptake or efflux, the mechanisms underlying bacterial resistance to excess zinc are unknown. In the present study, we searched for zinc-resistant mutant strains from the Keio collection, a gene knockout library of Escherichia coli, a model gram-negative bacteria. We found that knockout mutant of RpmJ (L36), a 50S ribosomal protein, exhibited zinc resistance. The rpmJ mutant was sensitive to protein synthesis inhibitors and had altered translation fidelity, indicating ribosomal dysfunction. In the rpmJ mutant, the intracellular zinc concentration was decreased under excess zinc conditions. Knockout of ZntA, a zinc efflux pump, abolished the zinc-resistant phenotype of the rpmJ mutant. RNA sequence analysis revealed that the rpmJ mutant exhibited altered gene expression of diverse functional categories, including translation, energy metabolism, and stress response. These findings suggest that knocking out RpmJ alters gene expression patterns and causes zinc resistance by lowering the intracellular zinc concentration. Knockouts of other ribosomal proteins, including RplA, RpmE, RpmI, and RpsT, also led to a zinc-resistant phenotype, suggesting that deletion of ribosomal proteins is closely related to zinc resistance.

锌是细胞必需的金属元素，但过量时会产生毒性。除了通过锌摄取或外排来调节细胞内锌浓度外，目前对细菌对抗过量锌的其他机制尚不明确。本研究从革兰氏阴性模式菌大肠杆菌（Escherichia coli）的基因敲除文库凯奥文库（Keio collection）中筛选耐锌突变菌株。研究发现，50S核糖体蛋白RpmJ（L36）的敲除突变体呈现耐锌表型。rpmJ突变体对蛋白质合成抑制剂敏感，且翻译保真度发生改变，提示核糖体功能异常。在过量锌条件下，rpmJ突变体的细胞内锌浓度有所降低。锌外排泵（zinc efflux pump）ZntA的敲除可消除rpmJ突变体的耐锌表型。RNA测序分析显示，rpmJ突变体的基因表达在翻译、能量代谢、应激反应等多个功能类别中均发生改变。上述结果表明，敲除RpmJ会改变基因表达模式，并通过降低细胞内锌浓度赋予细菌耐锌表型。包括RplA、RpmE、RpmI及RpsT在内的其他核糖体蛋白的敲除同样可诱导耐锌表型，提示核糖体蛋白缺失与耐锌表型密切相关。