In many pathogenic Gram-negative bacteria, such as Salmonella, Escherichia coli, Yersinia and Chlamydia spp., which cause diseases in humans, the type III secretion system (TTSS) is an important virulence factor that translocates effector proteins into the cytosol of host cells. Thus, the TTSS is a good target for antibacterial agents. Here we used a hemolysis assay to search for TTSS inhibitors and found that a compound from Magnolia obovata called obovatol blocks the TTSS of Salmonella. Obovatol showed potent inhibitory activity (IC₅₀=19.8 μM) against the TTSS-related hemolysis of Salmonella, which was not due to a reduction of bacterial growth. Instead, the compound inhibited bacterial motility, TTSS-related mRNA expression and effector protein secretion. These data demonstrate the inhibitory effect of obovatol on the Salmonella TTSS and suggest that it could be useful for the prevention and supplementary treatment of bacterial infections.

中文翻译：

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厚朴木的厚朴酚对III型沙门氏菌分泌系统的抑制作用。

在许多致病性革兰氏阴性细菌中，例如沙门氏菌，大肠杆菌，耶尔森氏菌和衣原体，会导致人类疾病，III型分泌系统（TTSS）是一种重要的毒力因子，可将效应子蛋白转移到宿主细胞的细胞质中。因此，TTSS是抗菌剂的良好靶标。在这里，我们使用溶血测定法来寻找TTSS抑制剂，并发现了一种名为obovatol的厚朴木兰化合物，它可以阻断沙门氏菌的TTSS。Obovatol显示出有效的抑制活性（IC ₅₀沙门氏菌与TTSS相关的溶血反应的速率为19.8μM），这不是由于细菌生长的减少引起的。相反，该化合物抑制细菌运动，TTSS相关的mRNA表达和效应蛋白分泌。这些数据证明了奥波托尔对沙门氏菌TTSS的抑制作用，并表明它可能对预防和补充治疗细菌感染有用。