Amino acid and C1 carbon source metabolism in the Salmonella typhimurium phagosome: Role of amino acids and glycine conversion in intracellular growth

鼠伤寒沙门氏菌吞噬体中的氨基酸和 C1 碳源代谢：氨基酸和甘氨酸转化在细胞内生长中的作用

• 批准号: 71738867
• 负责人: Dr. Karsten Tedin, Ph.D.
• 金额: --
• 依托单位: Institut für Mikrobiologie und Tierseuchen (WE07)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/71738867?language=en
• 关键词: Amino; acid; C1; carbon; source

We constructed a unique collection of mutants of Salmonella typhimurium defective in amino acid biosynthesis and uptake, peptide and oligopeptide uptake and amino acid catabolism and determined their intracellular growth characteristics in intestinal epithelial cells. Our studies showed that intracellular Salmonella not only have access to host-derived amino acid pools but are also capable of using peptides to satisfy amino acid requirements in the absence of biosynthetic and uptake systems. One exception is a strain with a mutation in glyA, encoding serine hydroxymethyltransferase (SHMT), responsible for the reversible conversion of serine to glycine, which shows a severe intracellular growth defect. In culture, glycine can correct the growth defect of a glyA mutant in glucose minimal medium; however, within host cells, a glyA mutant shows a severe growth defect. In addition, we found that the attenuation of aroA mutant strains of Salmonella is not due to defects in aromatic amino acid biosynthesis, but likely limitations in para-aminobenzoic acid, also derived from the same precursor, chorismic acid. Mutants defective in biosynthesis of all three aromatic amino acids show no intracellular growth defects, whereas mutants in pabA, pabB and/or pabC show severe growth defects within host cells. Finally, a previously uncharacterized gene, ltaA, was found to play a central role in maintaining intracellular growth by regulating the flow of threonine into either the glycine or branched chain amino acid pathways. The results indicate that intracellular Salmonella preferentially acquires amino acids from the host to maximize intracellular growth, and shows a high dependence on maintenance of amino acid pools involved in C1 carbon unit biosynthesis.

我们构建了氨基酸生物合成和摄取、肽和寡肽摄取以及氨基酸分解代谢缺陷的鼠伤寒沙门氏菌突变体的独特集合，并确定了它们在肠上皮细胞中的细胞内生长特征。我们的研究表明，细胞内沙门氏菌不仅可以获取宿主来源的氨基酸库，而且还能够在缺乏生物合成和摄取系统的情况下使用肽来满足氨基酸需求。一个例外是 glyA 突变的菌株，编码丝氨酸羟甲基转移酶 (SHMT)，负责丝氨酸可逆转化为甘氨酸，显示出严重的细胞内生长缺陷。在培养中，甘氨酸可以纠正glyA突变体在葡萄糖基本培养基中的生长缺陷；然而，在宿主细胞内，glyA 突变体表现出严重的生长缺陷。此外，我们发现沙门氏菌aroA突变株的减毒并非由于芳香族氨基酸生物合成的缺陷，而可能是由于对氨基苯甲酸的限制，对氨基苯甲酸也源自相同的前体分支酸。所有三种芳香族氨基酸生物合成缺陷的突变体均未表现出细胞内生长缺陷，而pabA、pabB和/或pabC中的突变体在宿主细胞内表现出严重的生长缺陷。最后，发现一个先前未表征的基因ltaA通过调节苏氨酸流入甘氨酸或支链氨基酸途径在维持细胞内生长中发挥核心作用。结果表明，细胞内沙门氏菌优先从宿主获取氨基酸，以最大限度地促进细胞内生长，并显示出对参与 C1 碳单元生物合成的氨基酸库的维持的高度依赖性。