Bordetella pertussis uses a type III secretion system (T3SS) to inject virulence proteins into host cells. Although the B. pertussis T3SS was presumed to be involved in host colonization, efficient secretion of type III secreted proteins from B. pertussis has not been observed. To investigate the roles of type III secreted proteins during infection, we attempted to optimize culture conditions for the production and secretion of a type III secreted protein, BteA, in B. pertussis. We observed that B. pertussis efficiently secretes BteA in ascorbic acid-depleted (AsA⁻) medium. When L2 cells, a rat lung epithelial cell line, were infected with B. pertussis cultured in the AsA⁻ medium, BteA-dependent cytotoxicity was observed. We also performed an immunofluorescence assay of L2 cells infected with B. pertussis. Clear fluorescence signals of Bsp22, a needle structure of T3SS, were detected on the bacterial surface of B. pertussis cultured in the AsA⁻ medium. Since ascorbic acid is known as a reducing agent, we cultured B. pertussis in liquid medium containing other reducing agents such as 2-mercaptoethanol and dithioerythritol. Under these reducing conditions, the production of type III secreted proteins was repressed. These results suggest that in B. pertussis, the production and secretion of type III secreted proteins are downregulated under reducing conditions.

中文翻译：

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百日咳博德特氏菌在还原条件下III型分泌系统的转录下调。

百日咳博德特氏菌使用III型分泌系统（T3SS）将毒力蛋白注入宿主细胞。虽然百日咳B. T3SS推测参与宿主定植，III型的有效分泌分泌的蛋白质从百日咳博德特氏菌尚未观察。为了研究感染期间III型分泌蛋白的作用，我们尝试优化培养条件，以在百日咳博德特氏菌中生产和分泌III型分泌蛋白BteA 。我们观察到，百日咳菌有效地抗坏血酸耗尽（ASA分泌BTEA ^- ）培养基。当L2细胞（一种大鼠肺上皮细胞系）感染百日咳博德特氏菌在抗坏血酸培养^-介质时，观察到BTEA体依赖性细胞毒性。我们还对百日咳杆菌感染的L2细胞进行了免疫荧光测定。Bsp22，T3SS的针结构的清晰的荧光信号，被的细菌表面上检测到百日咳博德特氏菌在培养抗坏血酸^-平台。由于抗坏血酸被称为还原剂，因此我们在含有其他还原剂（例如2-巯基乙醇和二硫赤藓糖醇）的液体培养基中培养百日咳博德特氏菌。在这些还原条件下，III型分泌蛋白的产生受到抑制。这些结果表明在百日咳博德特氏菌中，在还原条件下III型分泌蛋白的产生和分泌被下调。