Santos Fernanda F, Yamamoto Denise, Abe Cecilia M, Bryant Jack A, Hernandes Rodrigo T, Kitamura Felipe C, Castro Felipe S, Valiatti Tiago B, Piazza Roxane M F, Elias Waldir P, Henderson Ian R, Gomes Tânia A T
Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil.
Laboratório de Bacteriologia, Instituto Butantan, São Paulo, Brazil.
Front Microbiol. 2019 Jul 9;10:1527. doi: 10.3389/fmicb.2019.01527. eCollection 2019.
The intimin protein is the major adhesin involved in the intimate adherence of atypical enteropathogenic (aEPEC) strains to epithelial cells, but little is known about the structures involved in their early colonization process. A previous study demonstrated that the type III secretion system (T3SS) plays an additional role in the adherence of an strain. Therefore, we assumed that the T3SS could be related to the adherence efficiency of aEPEC during the first stages of contact with epithelial cells. To test this hypothesis, we examined the adherence of seven aEPEC strains and their (intimin) isogenic mutants in the standard HeLa adherence assay and observed that all wild-type strains were adherent while five isogenic mutants were not. The two mutant strains that remained adherent were then used to generate the / double mutants (encoding intimin and the T3SS ATPase, respectively) and after the adherence assay, we observed that one strain lost its adherence capacity. This suggested a role for the T3SS in the initial adherence steps of this strain. In addition, we demonstrated that this strain expressed the T3SS at significantly higher levels when compared to the other wild-type strains and that it produced longer translocon-filaments. Our findings reveal that the T3SS-translocon can play an additional role as an adhesin at the beginning of the colonization process of aEPEC.
紧密黏附素蛋白是参与非典型肠道致病性大肠杆菌（aEPEC）菌株与上皮细胞紧密黏附的主要黏附素，但对于其早期定植过程中涉及的结构却知之甚少。先前的一项研究表明，III型分泌系统（T3SS）在某菌株的黏附中发挥了额外作用。因此，我们推测T3SS可能与aEPEC在与上皮细胞接触的最初阶段的黏附效率有关。为了验证这一假设，我们在标准的HeLa细胞黏附试验中检测了7株aEPEC菌株及其（紧密黏附素）同基因缺失突变体的黏附情况，观察到所有野生型菌株均具有黏附能力，而5株同基因缺失突变体则没有。然后，我们利用仍具有黏附能力的2株缺失突变体菌株构建了/双突变体（分别编码紧密黏附素和T3SS ATP酶），在黏附试验后，我们观察到其中1株菌株失去了黏附能力。这表明T3SS在该菌株的初始黏附步骤中发挥了作用。此外，我们还证明，与其他野生型菌株相比，该菌株表达T3SS的水平显著更高，并且产生的转位子丝更长。我们的研究结果表明，在aEPEC的定植过程开始时，T3SS转位子可以作为一种黏附素发挥额外作用。
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