Wachtel M R, Miller V L
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095, USA.
Infect Immun. 1995 Jul;63(7):2541-8. doi: 10.1128/iai.63.7.2541-2548.1995.
Ail is a 17-kDa protein of Yersinia enterocolitica previously identified on the basis of its ability to confer upon Escherichia coli the phenotype of attachment and invasion of cultured epithelial cells. Here we report an examination of the contribution of ail to the pathogenicity of Y. enterocolitica. A low-copy-number ail plasmid that promoted serum resistance in E. coli HB101 was constructed. The serum resistance phenotype conferred by ail to E. coli was affected by the growth phase of the culture as well as by the gene copy number. In contrast, the copy number of ail (and the relative quantity of Ail) was found to have little effect on the amount of Ail-promoted invasion of cultured epithelial cells. An ail mutant of Y. enterocolitica was constructed and characterized in vitro. This mutant produced no detectable Ail and had a reduced ability to invade CHO cells. Serum resistance of Y. enterocolitica was Ail dependent and was affected by growth phase and ail copy number. The phenotype of the ail mutant was examined in vivo by using a murine model for infection. The ail mutant phenotype was identical to that of the wild-type strain in oral 50% lethal dose studies and early colonization of Peyer's patches as well as in kinetic studies. Western blot (immunoblot) analysis of Ail produced by bacteria growing in vivo at 48 h postinfection indicated that ail was expressed at this time point. Thus, our findings confirm that Ail contributes to the serum resistance and invasion phenotypes of Y. enterocolitica in vitro and indicate that Ail is not required to establish an infection or to cause systemic infection of BALB/c or DBA/2 mice.
Ail是小肠结肠炎耶尔森菌的一种17 kDa蛋白，此前是根据其赋予大肠杆菌培养上皮细胞附着和侵袭表型的能力而鉴定出来的。在此，我们报告了对Ail在小肠结肠炎耶尔森菌致病性中所起作用的研究。构建了一种在大肠杆菌HB101中促进血清抗性的低拷贝数Ail质粒。Ail赋予大肠杆菌的血清抗性表型受培养物生长阶段以及基因拷贝数的影响。相比之下，发现Ail的拷贝数（以及Ail的相对量）对Ail促进的培养上皮细胞侵袭量影响很小。构建了小肠结肠炎耶尔森菌的Ail突变体并在体外进行了表征。该突变体未产生可检测到的Ail，侵袭CHO细胞的能力降低。小肠结肠炎耶尔森菌的血清抗性依赖于Ail，并受生长阶段和Ail拷贝数的影响。通过使用小鼠感染模型在体内检查了Ail突变体的表型。在口服50%致死剂量研究、派伊尔结的早期定植以及动力学研究中，Ail突变体的表型与野生型菌株相同。对感染后48小时在体内生长的细菌产生的Ail进行蛋白质免疫印迹（免疫印迹）分析表明，此时Ail表达。因此，我们的研究结果证实Ail在体外对小肠结肠炎耶尔森菌的血清抗性和侵袭表型有贡献，并表明建立感染或引起BALB/c或DBA/2小鼠的全身感染不需要Ail。
