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.

我们构建了一株氨基酸生物合成和摄取、多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，并测定了它们在肠上皮细胞中的生长特性。我们的研究表明，细胞内沙门氏菌不仅可以进入宿主来源的氨基酸池，而且能够在没有生物合成和摄取系统的情况下利用多肽来满足氨基酸需求。一个例外是编码丝氨酸羟甲基转移酶(SHMT)的GlyA突变的菌株，它负责丝氨酸到甘氨酸的可逆转换，这显示出严重的细胞内生长缺陷。在培养过程中，甘氨酸可以纠正突变株在低糖条件下的生长缺陷，但在宿主细胞内，突变株表现出严重的生长缺陷。此外，我们还发现，沙门氏菌AROA突变株的衰减不是由于芳香族氨基酸生物合成的缺陷，而是对氨基苯甲酸的限制，对氨基苯甲酸也来自相同的前体--分支酸。三种芳香族氨基酸生物合成缺陷的突变株在细胞内没有生长缺陷，而PABA、pabB和/或PABC的突变株在宿主细胞内表现出严重的生长缺陷。最后，一个以前未被描述的基因，LTAA，被发现通过调节苏氨酸流向甘氨酸或支链氨基酸途径，在维持细胞内生长方面发挥核心作用。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，并表现出对参与C1C单位生物合成的氨基酸库的高度依赖。