Membrane vesicles (MVs) are nanoscale particles secreted by living bacteria in vitro and in vivo. Bacterial MVs encapsulate various proteins, making them promising candidates for developing vaccines, drug carriers, and cancer immunotherapy agents. However, the mechanisms underlying MV secretion in Gram-positive bacteria remain unclear. Here, we showed that the subinhibitory concentration of oxacillin (OXA) stimulated MV production in Staphylococcus aureus with diverse genetic backgrounds. OXA treatment remarkably increased the expression of sle1, which encodes a main peptidoglycan hydrolase for adjusting peptidoglycan cross-linking. Deletion of sle1 decreased the OXA-mediated MV yield, whereas overexpression of sle1 considerably increased MV production. The accessory regulator SarA increased in response to OXA treatment, and SarA inactivation substantially attenuated OXA-stimulated MV production. We also demonstrated that SarA controlled sle1 expression by directly binding to its promoter region. Thus, the SarA–Sle1 regulatory axis was formed to mediate OXA-induced MV production in S. aureus. MVs derived from OXA-treated S. aureus RN4220 (MVs/OXA) exhibited a smaller particle size compared with those purified from wild-type RN4220; however, proteomic analysis revealed a comparable protein profile between MVs and MVs/OXA. Overall, our research reveals a mechanism underlying OXA-promoted S. aureus MV secretion and highlights the potential application of OXA-induced MVs.

中文翻译：

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苯唑西林通过 SarA-Sle1 调节级联反应促进金黄色葡萄球菌中的膜囊泡分泌


膜囊泡 （MV） 是活细菌在体外和体内分泌的纳米级颗粒。细菌 MV 封装了各种蛋白质，使其成为开发疫苗、药物载体和癌症免疫治疗剂的有希望的候选者。然而，革兰氏阳性菌中 MV 分泌的机制仍不清楚。在这里，我们表明苯唑西林 （OXA） 的亚抑制浓度刺激具有不同遗传背景的金黄色葡萄球菌 MV 的产生。OXA 处理显着增加了 sle1 的表达，sle1 编码一种主要的肽聚糖水解酶，用于调节肽聚糖交联。sle1 的缺失降低了 OXA 介导的 MV 产量，而 sle1 的过表达显着增加了 MV 的产生。辅助调节因子 SarA 响应 OXA 处理而增加，而 SarA 失活显着减弱了 OXA 刺激的 MV 产生。我们还证明 SarA 通过直接结合其启动子区域来控制 sle1 表达。因此，SarA-Sle1 调节轴的形成是为了介导 OXA 诱导的金黄色葡萄球菌 MV 的产生。与从野生型 RN4220 中纯化的 MV 相比，来自 OXA 处理的金黄色葡萄球菌 RN4220 （MVs/OXA） 衍生的 MV 表现出更小的粒径;然而，蛋白质组学分析显示 MVs 和 MVs/OXA 之间的蛋白质谱相当。总体而言，我们的研究揭示了 OXA 促进金黄色葡萄球菌 MV 分泌的机制，并强调了 OXA 诱导的 MV 的潜在应用。