Leclerc Jean-Mathieu, Quevillon Eve-Lyne, Houde Yoan, Paranjape Kiran, Dozois Charles M, Daigle France
Department of Microbiology, Infectiology and Immunology, Université de Montréal,CP 6128 Succursale Centre-Ville, Montreal, Quebec H3C 3J7,Canada.
INRS-Institut Armand-Frappier,531 boulevard des Prairies, Laval, Québec H7V 1B7,Canada.
Microbiology (Reading). 2016 May;162(5):777-788. doi: 10.1099/mic.0.000270. Epub 2016 Mar 4.
tcf (Typhi colonization factor) is one of the 12 putative chaperone/usher fimbrial clusters present in the Salmonella enterica serovar Typhi genome. We investigated the production, expression and regulation of tcf as well as its role during interaction with human cells. The tcf gene cluster was cloned and induced in Escherichia coli and S. Typhi, and the production of intertwined fibres similar to the Cbl (cable) pili of Burkholderia cepacia was observed on the bacterial surface by electron microscopy. In S. Typhi, tcf was expressed more after growth in M63 minimal medium than in standard Luria-Bertani medium. Analysis of the promoter region identified putative binding sites for the global regulators RcsB, ArgR and Fur. The expression of tcf was measured in isogenic strains lacking these global regulators. Under the conditions tested, the results showed that tcf expression was higher in the fur mutant and was regulated by iron concentration. Fur may regulate these fimbriae indirectly via the small RNAs RyhB1 and RyhB2. An isogenic mutant harbouring a deletion of the tcf cluster did not demonstrate any defect in adhesion or invasion of human epithelial cells, or in phagocytosis or survival in macrophages, when compared to the WT serovar Typhi strain. However, the tcf cluster contributed to adherence to human epithelial cells when introduced into E. coli. Thus, tcf genes encode functional fimbriae that can act as an adhesin and may contribute to colonization during typhoid fever.
tcf（伤寒菌定植因子）是伤寒沙门氏菌基因组中存在的12个假定的伴侣/ usher菌毛簇之一。我们研究了tcf的产生、表达和调控及其在与人类细胞相互作用过程中的作用。tcf基因簇在大肠杆菌和伤寒沙门氏菌中进行克隆和诱导，通过电子显微镜观察到细菌表面产生了类似于洋葱伯克霍尔德菌Cbl（电缆）菌毛的交织纤维。在伤寒沙门氏菌中，tcf在M63基本培养基中生长后的表达比在标准的Luria-Bertani培养基中更高。对启动子区域的分析确定了全局调节因子RcsB、ArgR和Fur的假定结合位点。在缺乏这些全局调节因子的同基因菌株中测量了tcf的表达。在测试条件下，结果表明tcf在fur突变体中的表达更高，并且受铁浓度调节。Fur可能通过小RNA RyhB1和RyhB2间接调节这些菌毛。与野生型伤寒沙门氏菌菌株相比，携带tcf簇缺失的同基因突变体在黏附或侵袭人上皮细胞、或在巨噬细胞中的吞噬作用或存活方面没有表现出任何缺陷。然而，当将tcf簇导入大肠杆菌时，它有助于黏附人上皮细胞。因此，tcf基因编码功能性菌毛，其可作为黏附素并可能在伤寒热期间有助于定植。
