Preferential packing of acidic glycosidases and proteases into Bacteroides outer membrane vesicles.
Preferential packing of acidic glycosidases and proteases into Bacteroides outer membrane vesicles.
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DOI：
10.1128/mbio.00909-14
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发表时间：
2014-03-11
期刊：
影响因子：
6.4
通讯作者：
Feldman MF
中科院分区：
文献类型：
--
作者：
Elhenawy W;Debelyy MO;Feldman MF
外膜囊泡（OMV）是革兰氏阴性菌外膜（OM）释放的球形膜状结构。OMV已被提出在致病和共生过程中发挥几种不同的作用。尽管OMV在几十年前就被描述过，但它们的生物发生是一个缺乏特征的过程。OMV是由主动机制还是由OM的被动分解产生的，仍然是一个有争议的问题。脆弱拟杆菌和多形拟杆菌是人类微生物群的重要成员。本研究对脆弱B. fragilis和多形B. thetaiotaomicron的OM和OMV的蛋白质组成进行了测定和比较。两种组分的SDS-PAGE分析揭示了显著不同的蛋白质谱。对脆弱B. fragilis中OM和OMV的蛋白质组学分析鉴定了仅在OMV中发现的40多种蛋白质和仅在OM中可检测到的30多种蛋白质。OMV特异性蛋白质组显示出高流行率的糖苷酶和蛋白酶，其中一些在体外显示出活性。对于多形B. thetaiotaomicron获得了类似的结果。大部分OMV专一性蛋白是酸性的。基于这些结果，我们提出，这些物种拥有专门的机器选择性包装酸性蛋白质到OMV。这些配备有水解酶的OMV可以帮助确保营养素，以使微生物群中存在的整个细菌群落受益，从而揭示细菌OMV的新功能。拟杆菌属的成员是人类宿主和肠道微生物群之间共生的关键参与者。已知其能够降解多种聚糖，而这些聚糖不是人糖苷酶的底物。裂解的聚糖可以被拟杆菌和其他微生物群成员利用，从而产生对宿主有益的短链脂肪酸。虽然已知拟杆菌属的成员分泌不同的水解酶，但它们的分泌途径仍不确定。在这篇文章中，我们发现B. fragilis和B. thetaiotaomicron优先包装大量的水解酶的外膜囊泡（OMV）。这些水解酶中的大多数是酸性的，并且仅在OMV中检测到。这表明拟杆菌中存在一种分子机制，负责根据其电荷选择OMV蛋白。我们认为OMV有助于肠道微生物群的建立和平衡。
Outer membrane vesicles (OMV) are spherical membranous structures released from the outer membrane (OM) of Gram-negative bacteria. OMV have been proposed to play several different roles during both pathogenesis and symbiosis. Despite the fact that OMV were described several decades ago, their biogenesis is a poorly characterized process. Whether OMV are produced by an active mechanism or by passive disintegration of the OM is a still matter of controversy. Bacteroides fragilis and Bacteroides thetaiotaomicron are important members of the human microbiota. In this work, we determined and compared the protein compositions of OM and OMV from B. fragilis and B. thetaiotaomicron. SDS-PAGE analysis of both fractions revealed dramatically different protein profiles. Proteomic analysis of OM and OMV in B. fragilis identified more than 40 proteins found exclusively in OMV and more than 30 proteins detectable only in the OM. The OMV-specific proteome showed a high prevalence of glycosidases and proteases, some of which were shown to be active in vitro. Similar results were obtained for B. thetaiotaomicron. Most of the OMV-exclusive proteins were acidic. Based on these results, we propose that these species possess machinery devoted to selectively pack acidic proteins into the OMV. These OMV equipped with hydrolytic enzymes could help in securing nutrients for the benefit of the whole bacterial community present in the microbiota, uncovering a novel function for bacterial OMV. The members of genus Bacteroides are key players in the symbiosis between the human host and the gut microbiota. It is known for its ability to degrade a wide variety of glycans that are not substrates for human glycosidases. The cleaved glycans can be utilized by Bacteroides and other microbiota members, resulting in the production of short-chain fatty acids that are beneficial for the host. Although members of the genus Bacteroides are known to secrete different hydrolases, their secretion pathways remain uncharacterized. In this article, we show that B. fragilis and B. thetaiotaomicron preferentially pack a large number of hydrolases in outer membrane vesicles (OMV). Most of these hydrolases are acidic and were detected exclusively in OMV. This suggests the presence of a molecular mechanism in Bacteroides responsible for the selection of OMV proteins based on their charge. We propose that OMV contribute to the establishment and balance of the gut microbiota.