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首页> 外文期刊>Infection and immunity >The Alternative Sigma Factor, ?E, Is Critically Important for the Virulence of Salmonella typhimurium
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The Alternative Sigma Factor, ?E, Is Critically Important for the Virulence of Salmonella typhimurium

机译：替代西格玛因子？E对于鼠伤寒沙门氏菌的毒力至关重要

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In Escherichia coli, extracytoplasmic stress is partially controlled by the alternative sigma factor, RpoE (?E). In response to environmental stress or alteration in the protein content of the cell envelope, ?Eupregulates the expression of a number of genes, includinghtrA. It has been shown that htrA is required for intramacrophage survival and virulence in Salmonella typhimurium. To investigate whether ?E-regulated genes other than htrA are involved in salmonella virulence, we inactivated the rpoE gene of S. typhimurium SL1344 by allelic exchange and compared the phenotype of the mutant (GVB311) in vitro and in vivo with its parent and an isogenic htrA mutant (BRD915). UnlikeE. coli, ?E is not required for the growth and survival of S. typhimurium at high temperatures. However, GVB311 did display a defect in its ability to utilize carbon sources other than glucose. GVB311 was more sensitive to hydrogen peroxide, superoxide, and antimicrobial peptides than SL1344 and BRD915. Although able to invade both macrophage and epithelial cell lines normally, the rpoE mutant was defective in its ability to survive and proliferate in both cell lines. The effect of the rpoE mutation on the intracellular behavior of S. typhimurium was greater than that of the htrA mutation. Both GVB311 and BRD915 were highly attenuated in mice. Neither strain was able to kill mice via the oral route, and the 50% lethal dose (LD50) for both strains via the intravenous (i.v.) route was very high. The i.v. LD50s for SL1344, BRD915, and GVB311 were <10, 5.5 × 105, and 1.24 × 107 CFU, respectively. Growth in murine tissues after oral and i.v. inoculation was impaired for both thehtrA and rpoE mutant, with the latter mutant being more severely affected. Neither mutant was able to translocate successfully from the Peyer’s patches to other organs after oral infection or to proliferate in the liver and spleen after i.v. inoculation. However, the htrA mutant efficiently colonized the livers and spleens of mice infected i.v., but the rpoE mutant did not. Previous studies have shown that salmonella htrA mutants are excellent live vaccines. In contrast, oral immunization of mice with GVB311 was unable to protect any of the mice from oral challenge with SL1344. Furthermore, i.v. immunization with a large dose (～106 CFU) of GVB311 protected less than half of the orally challenged mice. Thus, our results indicate that genes in the ?E regulon other than htrA play a critical role in the virulence and immunogenicity of S. typhimurium.
机译：在大肠杆菌中，胞浆外应激部分受替代sigma因子RpoE（？ E ）的控制。响应环境压力或细胞膜蛋白含量的变化，α E 上调许多基因的表达，包括 htrA 。已经显示，鼠伤寒沙门氏菌中的巨噬细胞内生存和毒力需要 htrA 。为了研究除 htrA 以外的其他受 sup> E 调控的基因是否与沙门氏菌毒力有关，我们使 S的 rpoE 基因失活。通过等位基因交换研究鼠伤寒沙门氏菌 SL1344，并将该突变体（GVB311）的表型与其亲本和同基因的 htrA 突变体（BRD915）进行了体外和体内比较。与 E不同。 S的生长和存活不需要大肠杆菌，？ E 。高温下鼠伤寒。但是，GVB311在利用葡萄糖以外的碳源方面确实表现出缺陷。与SL1344和BRD915相比，GVB311对过氧化氢，超氧化物和抗菌肽更敏感。尽管能够正常侵袭巨噬细胞和上皮细胞系，但 rpoE 突变体在两种细胞系中均能生存和增殖。 rpoE 突变对 S的细胞内行为的影响。鼠伤寒大于 htrA 突变。 GVB311和BRD915在小鼠中均高度减毒。两种菌株均不能通过口服途径杀死小鼠，并且两种菌株通过静脉内（i.v.）途径的50％致死剂量（LD 50 ）很高。 i.v. SL1344，BRD915和GVB311的LD 50 分别为<10、5.5×10 5 和1.24×10 7 CFU。口服和静脉注射后鼠组织中的生长 htrA 和 rpoE 突变体的接种均受到损害，后者的突变受到的影响更大。口腔感染后，这两种突变体都无法成功地从Peyer斑块转移到其他器官，也不能在静脉内感染后在肝脏和脾脏中增殖。接种。但是， htrA 突变体可以有效地定居于静脉感染小鼠的肝脏和脾脏，而 rpoE 突变体却不能。先前的研究表明沙门氏菌 htrA 突变体是出色的活疫苗。相反，用GVB311进行的小鼠口服免疫不能保护任何小鼠免受SL1344的口服攻击。此外，i.v。大剂量（〜10 6 CFU）的GVB311免疫可以保护不到一半的经口攻击的小鼠。因此，我们的结果表明，除了 htrA 之外，？ E 调节子中的基因在 S的毒力和免疫原性中起关键作用。鼠伤寒。

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