Laboratory of Respiratory and Special Pathogens, Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, USA.
J Bacteriol. 2024 Jun 20;206(6):e0012424. doi: 10.1128/jb.00124-24. Epub 2024 May 29.
is the causative agent of diphtheria, a severe respiratory disease in humans. colonizes the human upper respiratory tract, where it acquires zinc, an essential metal required for survival in the host. While the mechanisms for zinc transport by are not well characterized, four putative zinc ABC-type transporter loci were recently identified in strain 1737: (), (), (), and (). A mutant deleted for all four loci (Δ4) exhibited similar growth to that of the wild-type strain in a zinc-limited medium, suggesting there are additional zinc transporters. Two additional gene loci predicted to be associated with metal import, () and () were deleted in the Δ4 mutant to construct a new mutant designated Δ6. The Δ6 mutant exhibited significantly reduced growth under zinc limitation relative to the wild type, suggesting a deficiency in zinc acquisition. Strains retaining the , , or loci grew to near-wild-type levels in the absence of the other five loci, indicating that each of these transporters may be involved in zinc uptake. Plasmid complementation with cloned , , , or loci also enhanced the growth of the Δ6 mutant. Quantification of intracellular zinc content by inductively coupled plasma mass spectrometry was consistent with reduced zinc uptake by Δ6 relative to the wild type and further supports a zinc uptake function for the transporters encoded by , , and . This study demonstrates that zinc transport is complex and involves multiple zinc uptake systems.IMPORTANCEZinc is a critical nutrient for all forms of life, including human bacterial pathogens. Thus, the tools that bacteria use to acquire zinc from host sources are crucial for pathogenesis. While potential candidates for zinc importers have been identified in from gene expression studies, to date, no study has clearly demonstrated this function for any of the putative transporters. We show that encodes at least six loci associated with zinc import, underscoring the extent of redundancy for zinc acquisition. Furthermore, we provide evidence that a previously studied manganese-regulated importer can also function in zinc import. This study builds upon our knowledge of bacterial zinc transport mechanisms and identifies potential targets for future diphtheria vaccine candidates.
白喉棒状杆菌是白喉的病原体，是一种严重的人类呼吸道疾病。它定植于人类上呼吸道，在那里它获取锌，这是在宿主体内生存所必需的一种关键金属。虽然 摄取锌的机制尚未很好地描述，但最近在菌株 1737 中鉴定出了四个假定的锌 ABC 型转运体基因座：（）、（）、（）和（）。一个缺失所有四个基因座的突变体（Δ4）在锌限制培养基中的生长与野生型菌株相似，表明还有其他锌转运体。另外两个预测与金属导入相关的基因座（）和（）在 Δ4 突变体中被删除，以构建一个新的突变体命名为 Δ6。与野生型相比，Δ6 突变体在锌限制下的生长显著减少，表明其在锌获取方面存在缺陷。在没有其他五个基因座的情况下，保留 、 、 或 基因座的菌株在锌限制下生长到接近野生型水平，表明这些转运体中的每一个都可能参与锌摄取。用克隆的 、 、 或 基因座的质粒互补也增强了 Δ6 突变体的生长。通过电感耦合等离子体质谱法对细胞内锌含量的定量分析与 Δ6 相对于野生型的锌摄取减少一致，进一步支持了这些转运体编码的转运体的锌摄取功能。本研究表明， 锌的转运是复杂的，涉及多个锌摄取系统。
重要性锌是所有生命形式（包括人类细菌病原体）的关键营养素。因此，细菌从宿主来源获取锌的工具对于发病机制至关重要。虽然已经从基因表达研究中确定了 中的潜在锌导入候选物，但迄今为止，没有研究清楚地证明任何假定的转运体都具有这种功能。我们表明， 至少编码与锌摄取相关的六个基因座，突出了锌摄取冗余的程度。此外，我们提供的证据表明，先前研究的锰调节导入器也可以在锌导入中发挥作用。这项研究建立在我们对细菌锌转运机制的认识之上，并确定了未来白喉疫苗候选物的潜在目标。
