Regulatory mechanisms of expression of SEp22, a noves pathogenicity-related factor of Salmonella Enteritidis, underlying penetration through intestinal membrane

在致病性肠炎沙门氏菌（Salmonella Enteritidis， SE）中，sep22基因在对数早期转录量很少，随后随着细菌生长逐渐增加，在对数晚期通常在接种细菌至新鲜LB培养基后6-8 h达到最大值。另一方面，沙门氏菌的典型毒力因子invA，也是III型分泌系统（TTSS）的重要成员，在细菌开始培养后迅速表达，通常在培养后1-2 h达到最大值，随后逐渐降低直至静止期。这些结果表明，sep22和invA在致病性沙门氏菌细胞中表现出明显不同的调控作用，在沙门氏菌感染宿主细胞的过程中发挥着不同的作用，即sep22作为一种保护因子，对来自宿主的杀伤效应分子起保护作用。后者则是对主人的一种冒犯。一些证明sep22在沙门氏菌感染中的关键作用的试验正在进行中，使用KO-5菌株（sep22基因敲除SE的突变体）建立逆转录物。对于参与SEp22表达的营养因子，我们在LB培养基、酪胺酸、白菜提取物、胎牛血清、蛋黄等中对部分营养因子进行了表征。多种分子被证明是有效的营养因子，并且利用高效液相色谱法纯化了酪胺酸中的一些分子。此外，SEp22蛋白表达在SE菌株中对致病性SE对巨噬细胞的粘附起负作用，但在SE菌株中对Caco-2细胞的感染过程中SEp22蛋白表达无显著差异，提示SEp22在沙门氏菌的发病过程中具有多种调节作用。

In a pathogenic strain of Salmonella Enteritidis, (SE), sep22 gene was transcribed very little in early logarithmic phase, then became gradually increased in accordance with the bacterial growth, reaching maximal at the late logarithmic phase usually 6-8 h after inoculation of the bacteria in to fresh LB medium. On the other hand, a typical virulent factor of Salmonella, invA, which is also an important member of Type III secretion system (TTSS), became rapidly expressed after starting cultivation of the bacteria, and became maximal usually 1-2 h after incubation, followed by gradual decrease until stational phase. These results suggest that sep22 and invA show quite distinct regulation in a pathogenic Salmonella cell, which should exert different roles during establishing infection of Salmonella to host cells, i.e., the former, working as a protective factor against killing effector molecules from the host., and the latter, working as an offense factor toward the host. Some trials to prove the pivotal role of sep22 in Salmonella infection are in progress to establish revertants using KO-5 strain, a sep22-gene knock out mutant of SE. Regarding nutritional factors involved in SEp22 expression, we characterized some of them in LB medium, casamino acids, cabbage extracts, fetal bovine serum, egg yolk and so on. A variety of molecules were shown to be effective as a nutritional factors, and some molecules in casamino acids have been purified using HPLC. Besides, SEp22 protein expression in SE strains was shown to be playing negative roles in adhesion of pathogenic SE to macrophages but also positive roles in invasion to the macrophages, although that in SE showed no significant differences in the course of SE infection to Caco-2 cells, suggesting multiple regulatory roles of SEp22 in Salmonella pathogenesis.