Abstract：
Microbes encounter a myriad of stresses during their life cycle. Dysregulation of metal ion homeostasis is increasingly recognized as a key factor in host-microbe interactions. Bacterial metal ion homeostasis is tightly regulated by dedicated metalloregulators that control uptake, sequestration, trafficking, and efflux. Here, we demonstrate that deletion of the Bacillus subtilis yqgC-sodA (YS) complex operon, but not deletion of the individual genes, causes hypersensitivity to manganese (Mn). YqgC is an integral membrane protein of unknown function, and SodA is a Mn-dependent superoxide dismutase (MnSOD). The YS strain has reduced expression of two Mn efflux proteins, MneP and MneS, consistent with the observed Mn sensitivity. The YS strain accumulated high levels of Mn, had increased reactive radical species (RRS), and had broad metabolic alterations that can be partially explained by the inhibition of Mg-dependent enzymes. Although the YS operon deletion strain and an efflux-deficient mneP mneS double mutant both accumulate Mn and have similar metabolic perturbations, they also display phenotypic differences. Several mutations that suppressed Mn intoxication of the mneP mneS efflux mutant did not benefit the YS mutant. Further, Mn intoxication in the YS mutant, but not the mneP mneS strain, was alleviated by expression of Mg-dependent, chorismate-utilizing enzymes of the menaquinone, siderophore, and tryptophan (MST) family. Therefore, despite their phenotypic similarities, the Mn sensitivity in the mneP mneS and the YS deletion mutants results from distinct enzymatic vulnerabilities.IMPORTANCEBacteria require multiple trace metal ions for survival. Metal homeostasis relies on the tightly regulated expression of metal uptake, storage, and efflux proteins. Metal intoxication occurs when metal homeostasis is perturbed and often results from enzyme mis-metalation. In Bacillus subtilis, Mn-dependent superoxide dismutase (MnSOD) is the most abundant Mn-containing protein and is important for oxidative stress resistance. Here, we report novel roles for MnSOD and a co-regulated membrane protein, YqgC, in Mn homeostasis. Loss of both MnSOD and YqgC (but not the individual proteins) prevents the efficient expression of Mn efflux proteins and leads to a large-scale perturbation of the metabolome due to inhibition of Mg-dependent enzymes, including key chorismate-utilizing MST (menaquinone, siderophore, and tryptophan) family enzymes.
摘要：
微生物在其生命周期中遇到无数的压力。金属离子稳态的失调越来越被认为是宿主-微生物相互作用的关键因素。细菌金属离子稳态由控制摄取的专用金属调节剂严格调节，封存，贩运，和外排。这里,我们证明了枯草芽孢杆菌yqgC-sodA（YS）复杂操纵子的缺失，但不是单个基因的缺失，对锰（Mn）过敏。YqgC是一种功能未知的完整膜蛋白，SodA是一种依赖锰的超氧化物歧化酶(MnSOD)。YS菌株降低了两种Mn外排蛋白的表达，MneP和MneS，与观察到的Mn敏感性一致。YS菌株积累了高水平的Mn，增加了反应性自由基种类(RRS)，并且具有广泛的代谢改变，可以部分通过Mg依赖性酶的抑制来解释。尽管YS操纵子缺失菌株和外排缺陷型mnePmneS双突变体都积累了Mn并具有相似的代谢扰动，它们还表现出表型差异。抑制MnePMneS外排突变体的Mn中毒的几种突变对YS突变体没有好处。Further,YS突变体中的锰中毒，但不是mnePmneS菌株，通过Mg依赖的表达来缓解，甲基萘醌中利用胆碱的酶，铁载体,和色氨酸（MST）家族。因此,尽管它们的表型相似，MnePMneS和YS缺失突变体中的Mn敏感性是由不同的酶脆弱性引起的。重要细菌需要多种痕量金属离子才能生存。金属稳态依赖于金属摄取的严格调控表达，storage,和外排蛋白。当金属稳态受到干扰时，就会发生金属中毒，并且通常是由酶的金属误化引起的。在枯草芽孢杆菌中,Mn依赖性超氧化物歧化酶（MnSOD）是最丰富的含Mn蛋白，对于抗氧化应激很重要。这里,我们报道了MnSOD和共调节膜蛋白的新作用，YqgC,在锰稳态中。MnSOD和YqgC（但不是单个蛋白质）的丢失会阻止Mn外排蛋白的有效表达，并由于Mg依赖性酶的抑制而导致代谢组的大规模扰动。包括利用主要分支物质的MST(甲基萘醌，铁载体,和色氨酸）家族酶。
