Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.
Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
J Bacteriol. 2020 Sep 23;202(20). doi: 10.1128/JB.00233-20.
is the leading cause of hospital-acquired antibiotic-associated diarrhea and is the only widespread human pathogen that contains a complete set of genes encoding the Wood-Ljungdahl pathway (WLP). In acetogenic bacteria, synthesis of acetate from 2 CO molecules by the WLP functions as a terminal electron accepting pathway; however, contains various other reductive pathways, including a heavy reliance on Stickland reactions, which questions the role of the WLP in this bacterium. In rich medium containing high levels of electron acceptor substrates, only trace levels of key WLP enzymes were found; therefore, conditions were developed to adapt to grow in the absence of amino acid Stickland acceptors. Growth conditions were identified that produce the highest levels of WLP activity, determined by Western blot analyses of the central component acetyl coenzyme A synthase (AcsB) and assays of other WLP enzymes. Fermentation substrate and product analyses, enzyme assays of cell extracts, and characterization of a Δ mutant demonstrated that the WLP functions to dispose of metabolically generated reducing equivalents. While WLP activity in does not reach the levels seen in classical acetogens, coupling of the WLP to butyrate formation provides a highly efficient system for regeneration of NAD "acetobutyrogenesis," requiring only low flux through the pathways to support efficient ATP production from glucose oxidation. Additional insights redefine the amino acid requirements in , explore the relationship of the WLP to toxin production, and provide a rationale for colocalization of genes involved in glycine synthesis and cleavage within the WLP operon. is an anaerobic, multidrug-resistant, toxin-producing pathogen with major health impacts worldwide. It is the only widespread pathogen harboring a complete set of Wood-Ljungdahl pathway (WLP) genes; however, the role of the WLP in is poorly understood. In other anaerobic bacteria and archaea, the WLP can operate in one direction to convert CO to acetic acid for biosynthesis or in either direction for energy conservation. Here, conditions are defined in which WLP levels in increase markedly, functioning to support metabolism of carbohydrates. Amino acid nutritional requirements were better defined, with new insight into how the WLP and butyrate pathways act in concert, contributing significantly to energy metabolism by a mechanism that may have broad physiological significance within the group of nonclassical acetogens.
是医院获得性抗生素相关性腹泻的主要原因，也是唯一广泛存在的人类病原体，其中包含一套完整的编码 Wood-Ljungdahl 途径（WLP）的基因。在产乙酸菌中，WLP 将 2 个 CO 分子合成乙酸，作为末端电子接受途径；然而， 包含各种其他还原途径，包括对 Stickland 反应的高度依赖，这质疑了 WLP 在该细菌中的作用。在含有高水平电子受体底物的丰富培养基中，只发现了痕量的关键 WLP 酶；因此，开发了条件来使 适应在没有氨基酸 Stickland 受体的情况下生长。确定了产生最高水平 WLP 活性的生长条件，通过 Western blot 分析中心成分乙酰辅酶 A 合酶（AcsB）和其他 WLP 酶的测定来确定。发酵底物和产物分析、细胞提取物的酶测定以及 Δ 突变体的特性表明，WLP 可用于处理代谢产生的还原当量。虽然 在 中的 WLP 活性未达到经典产乙酸菌中的水平，但 WLP 与丁酸盐形成的偶联提供了一种高效的系统，可用于 NAD 的再生“丁酸生成”，仅需低通量通过途径即可从葡萄糖氧化中支持高效的 ATP 产生。其他见解重新定义了 在 中的氨基酸需求，探讨了 WLP 与毒素产生的关系，并为甘氨酸合成和裂解基因在 WLP 操纵子内的共定位提供了合理依据。 是一种厌氧、多药耐药、产毒素的病原体，对全球健康有重大影响。它是唯一广泛存在的病原体，其中包含一套完整的 Wood-Ljungdahl 途径（WLP）基因；然而，WLP 在 中的作用知之甚少。在其他厌氧细菌和古菌中，WLP 可以沿一个方向运行，将 CO 转化为乙酸用于生物合成，或者沿两个方向运行用于能量保存。在这里，定义了 WLP 水平在 中显著增加的条件，该途径用于支持碳水化合物的代谢。更好地定义了氨基酸营养需求，并深入了解 WLP 和丁酸盐途径如何协同作用，通过一种可能在非经典产乙酸菌群体中具有广泛生理意义的机制，对能量代谢做出重大贡献。
