Temperature influences the composition and cytotoxicity of extracellular vesicles in Staphylococcus aureus

Staphylococcus aureus is a pathogenic bacterium but also a commensal of skin and anterior nares in humans. As S. aureus transits from skins/nares to inside the human body, it experiences changes in temperature. The production and content of S. aureus extracellular vesicles (EV) have been increasingly studied over the past few years and EVs are increasingly being recognized as important to the infectious process. Nonetheless, the impact of temperature variation on S. aureus EVs has not been studied in detail as most reports that investigate EV cargoes and host cell interactions are performed using vesicles produced at 37˚C. Here we report that S. aureus vesicle production is temperature-dependent with greater vesiculation at 40˚C. We demonstrate that the temperature dependent regulation of vesicle production in S. aureus is mediated by the alpha phenol soluble modulin peptides (αPSMs). Through proteomic analysis, we observed increased packaging of virulence factors at 40˚C whereas more total proteins are present in EVs produced at 34˚C. Similar to the protein content, we perform transcriptomic analysis and demonstrate that the RNA cargo is impacted by temperature also. Finally, we demonstrate greater αPSM- and α-toxin mediated erythrocyte lysis with 40˚C EVs but 34˚C EVs are more cytotoxic toward THP-1 cells. Together our study demonstrates that small temperature variations have great impact on EV biogenesis and shape the interaction with host cells.

金黄色葡萄球菌（Staphylococcus aureus）是一种致病菌，同时也是人类皮肤与前鼻腔的共生定植菌。当金黄色葡萄球菌从皮肤或鼻腔转移至人体内部时，其所处环境温度会发生改变。近数年来，针对金黄色葡萄球菌细胞外囊泡（extracellular vesicles, EV）的生成机制与内含物组成的研究持续增多，且EV在感染过程中的重要性也逐渐得到学界认可。然而，由于绝大多数探究EV内含载荷与宿主细胞相互作用的研究均采用37℃条件下制备的囊泡开展，温度变化对金黄色葡萄球菌EV的影响尚未得到详尽研究。本研究证实，金黄色葡萄球菌的囊泡生成过程具有温度依赖性，在40℃条件下囊泡生成量更高。我们证明，金黄色葡萄球菌囊泡生成的温度依赖性调控由α-酚溶性调节蛋白肽（alpha phenol soluble modulin peptides, αPSMs）介导。通过蛋白质组学分析，我们观察到40℃条件下囊泡中毒力因子的包装丰度更高，而34℃条件下生成的EV中总蛋白含量更为丰富。与蛋白内含物的变化规律类似，我们通过转录组学分析证实，EV的RNA载荷同样会受到温度的调控。最后我们证实，40℃条件下生成的EV介导的αPSM及α毒素相关红细胞裂解效应更强，而34℃条件下的EV对THP-1细胞系的细胞毒性更高。综上，本研究表明微小的温度变化会对EV的生物发生过程产生显著影响，并进而重塑其与宿主细胞的相互作用模式。