Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom.
Front Cell Infect Microbiol. 2019 May 29;9:177. doi: 10.3389/fcimb.2019.00177. eCollection 2019.
outer membrane vesicles (OMVs) contain numerous virulence-associated proteins including the cytolethal distending toxin and three serine proteases. As lacks the classical virulence-associated secretion systems of other enteric pathogens that deliver effectors directly into target cells, OMVs may have a particularly important role in virulence. OMV production is stimulated by the presence of physiological concentrations of the bile salt sodium taurocholate (ST) through an unknown mechanism. The maintenance of lipid asymmetry (MLA) pathway has been implicated in a novel mechanism for OMV biogenesis, open to regulation by host signals. In this study we investigated the role of the MLA pathway in OMV biogenesis with ST as a potential regulator. OMV production was quantified by analyzing protein and lipid concentrations of OMV preparations and OMV particle counts produced by nanoparticle tracking analysis. Mutation of which encodes the outer membrane component of the MLA pathway significantly increased OMV production compared to the wild-type strain. Detergent sensitivity and membrane permeability assays confirmed the increased OMV production was not due to changes in membrane stability. The presence of 0.2% (w/v) ST increased wild-type OMV production and reduced OMV size, but did not further stimulate mutant OMV production or significantly alter mutant OMV size. qRT-PCR analysis demonstrated that the presence of ST decreased expression of both and in wild-type strains 11168 and 488. Collectively the data in this study suggests can regulate OMV production in response to host gut signals through changes in expression of the MLA pathway. As the gut bile composition is dependent on both diet and the microbiota, this study highlights the potential importance of diet and lifestyle factors on the varying disease presentations associated with gut pathogen infection.
外膜囊泡 (OMVs) 包含许多与毒力相关的蛋白质，包括细胞致死扩张毒素和三种丝氨酸蛋白酶。由于 缺乏其他肠道病原体将效应物直接递送到靶细胞的经典毒力相关分泌系统，因此 OMVs 在毒力中可能具有特别重要的作用。通过未知机制，生理浓度的胆汁盐牛磺胆酸钠 (ST) 刺激 OMV 的产生。脂质不对称性 (MLA) 途径的维持与 OMV 生物发生的一种新机制有关，该机制可受宿主信号的调节。在这项研究中，我们研究了 MLA 途径在 ST 作为潜在调节剂的 OMV 生物发生中的作用。通过分析 OMV 制剂的蛋白质和脂质浓度以及纳米颗粒跟踪分析产生的 OMV 颗粒计数来定量 OMV 的产生。与野生型菌株相比，编码 MLA 途径的外膜成分的 突变显著增加了 OMV 的产生。去污剂敏感性和膜通透性测定证实，增加的 OMV 产量不是由于膜稳定性的变化。存在 0.2%（w/v）ST 增加了野生型 OMV 的产生并减少了 OMV 的大小，但没有进一步刺激 突变体 OMV 的产生或显著改变 突变体 OMV 的大小。qRT-PCR 分析表明，ST 的存在降低了 11168 和 488 两种野生型菌株中 和 的表达。总的来说，这项研究的数据表明， 可以通过改变 MLA 途径的表达来响应宿主肠道信号调节 OMV 的产生。由于肠道胆汁组成既依赖于饮食，也依赖于微生物群，因此这项研究强调了饮食和生活方式因素对与肠道病原体感染相关的不同疾病表现的潜在重要性。
