Pyruvate Oxidase as a Critical Link between Metabolism and Capsule Biosynthesis in Streptococcus pneumoniae.
Pyruvate Oxidase as a Critical Link between Metabolism and Capsule Biosynthesis in Streptococcus pneumoniae.
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DOI：
10.1371/journal.ppat.1005951
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发表时间：
2016-10
期刊：
影响因子：
6.7
通讯作者：
Rosch JW
中科院分区：
文献类型：
--
作者：
Echlin H;Frank MW;Iverson A;Chang TC;Johnson MD;Rock CO;Rosch JW
肺炎球菌是细菌病原体中产生过氧化氢最多的细菌之一。过氧化氢的产生与抗生素的协同作用、鼻咽部其他细菌定植体之间的竞争以及对上皮细胞的损伤有关。然而，在侵袭性疾病中的作用尚不清楚，过氧化氢产生缺陷的突变体根据菌株和血清型背景显示出侵袭性疾病能力的衰减和增强。这项工作通过证明肺炎球菌的主要过氧化氢产生酶SpxB，以菌株依赖的方式形成胶囊，解决了这些相互矛盾的观察结果。含有乙酰化糖胶囊的菌株的胶囊生产依赖于spxB的存在，而缺乏这种联系的血清型的胶囊生产则不依赖于spxB。spxB突变体的细胞稳态乙酰辅酶a水平显著降低，表明胶囊的丢失是由于这种中间代谢物的失调引起的。这一结论被pdhC的缺失所证实，pdhC的缺失也导致了稳态乙酰辅酶a水平的降低，并使spxB突变体的荚膜表达谱表型化。在spxB和lctO（乳酸氧化酶）双突变体中，胶囊和乙酰辅酶a水平恢复，支持中心代谢与胶囊形成之间的联系。综上所述，这些数据表明，spxB突变体的发病机制缺陷是由于代谢不平衡导致胶囊形成减少，而不是过氧化氢形成减少。肺炎球菌多糖胶囊是由这种主要的人类病原体产生的最关键的毒力决定因素之一。肺炎球菌还通过丙酮酸氧化酶（SpxB）催化的酶促反应产生大量的过氧化氢。spxB基因的缺失导致表面多糖荚膜的丧失，并以血清型依赖的方式对突变体的毒力产生镜像效应。我们观察到spxB的缺失降低了乙酰辅酶a的稳态水平，乙酰辅酶a是一部分血清型中肽聚糖、脂肪酸生物合成和胶囊生物合成的关键代谢中间体。这些数据表明，胶囊生产中的缺陷是由于代谢改变导致乙酰辅酶a可用性降低。为了证实这些数据，我们发现，当PDHC（一种产生乙酰辅酶a的额外代谢酶）丢失时，胶囊的生物合成受到损害。这些数据揭示了肺炎球菌代谢和胶囊生物合成之间的关键联系，并提供了一个惊人的例子，说明一个毒力基因如何根据菌株背景对发病机制有不同的贡献。
The pneumococcus is one of the most prodigious producers of hydrogen peroxide amongst bacterial pathogens. Hydrogen peroxide production by the pneumococcus has been implicated in antibiotic synergism, competition between other bacterial colonizers of the nasopharynx, and damage to epithelial cells. However, the role during invasive disease has been less clear with mutants defective in hydrogen peroxide production demonstrating both attenuation and heightened invasive disease capacity depending upon strain and serotype background. This work resolves these conflicting observations by demonstrating that the main hydrogen peroxide producing enzyme of the pneumococcus, SpxB, is required for capsule formation in a strain dependent manner. Capsule production by strains harboring capsules with acetylated sugars was dependent upon the presence of spxB while capsule production in serotypes lacking such linkages were not. The spxB mutant had significantly lower steady-state cellular levels of acetyl-CoA, suggesting that loss of capsule arises from dysregulation of this intermediary metabolite. This conclusion is corroborated by deletion of pdhC, which also resulted in lower steady-state acetyl-CoA levels and phenocopied the capsule expression profile of the spxB mutant. Capsule and acetyl-CoA levels were restored in the spxB and lctO (lactate oxidase) double mutant, supporting the connection between central metabolism and capsule formation. Taken together, these data show that the defect in pathogenesis in the spxB mutant is due to a metabolic imbalance that attenuates capsule formation and not to reduced hydrogen peroxide formation. The pneumococcus polysaccharide capsule is one of the most critical virulence determinants produced by this major human pathogen. The pneumococcus also produces prodigious amounts of hydrogen peroxide via the enzymatic reaction catalyzed by pyruvate oxidase, SpxB. Deletion of spxB resulted in the loss of surface polysaccharide capsule production in a serotype dependent manner with a mirrored effect on the virulence of the mutants. We observed that deletion of spxB reduced the steady-state levels of acetyl-CoA, a key metabolic intermediate in peptidoglycan, fatty acid biosynthesis, and in capsule biosynthesis in a subset of serotypes. These data suggest that the defect in capsule production was due to altered metabolism that results in reduced acetyl-CoA availability. Corroborating these data, we found that capsule biosynthesis was impaired upon loss of PDHC, an additional metabolic enzyme that generates acetyl-CoA. These data reveal a critical link between pneumococcal metabolism and capsule biosynthesis as well as provide a striking example of how a virulence gene can have a differential contribution to pathogenesis dependent upon strain background.
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影响因子：
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作者：
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DOI：
10.1016/j.bbalip.2010.06.004
发表时间：
2010-09-01
影响因子：
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作者：
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