Microbiology and Cell Science Department, IFAS, University of Florida, FL 32611, USA.
Microbiology and Cell Science Department, IFAS, University of Florida, FL 32611, USA.
J Proteomics. 2021 Jan 16;231:103994. doi: 10.1016/j.jprot.2020.103994. Epub 2020 Sep 29.
Outer membrane vesicles (OMVs) are membrane-enclosed spherical entities released by gram-negative bacteria and are important for bacterial survival under stress conditions. There have been numerous studies on OMVs released by gram-negative pathogenic bacteria, but an understanding of the functions and characteristics of the OMVs produced by commensal microbes is still lacking. Enterobacter cloacae is a gram-negative commensal bacterium present in the human gut microbiome, but this organism can also function as an opportunistic pathogen. Understanding the OMV-mediated communication route between bacteria-bacteria or bacteria-host is essential for the determination of the biological functions of the commensal bacterium in the gut and delineating between benign and virulent characteristics. In this study, we have described a proteome of E. cloacae OMVs, which are membrane vesicles in a size range of 20-300 nm. Proteomic analysis showed the presence of membrane-bound proteins, including transporters, receptors, signaling molecules, and protein channels. The physical and proteomic analyses also indicate this bacterium uses two mechanisms for OMV production. This study is one of the few existing descriptions of the proteomic profile of OMVs generated by a commensal Proteobacteria, and the first report of OMVs produced by E. cloacae. SIGNIFICANCE: This study prioritizes the importance of understanding the vesicular proteome of the human commensal bacterium, Enterobacter cloacae. We demonstrate for the first time that the gram-negative bacterium E. cloacae ATCC 13047 produces outer membrane vesicles (OMVs). The proteomic analysis showed enrichment of membrane-bound proteins in these vesicles. Understanding the cargo proteins of OMVs will help in exploring the physiological and functional role of these vesicles in the human microbiome and how they assist in the conversion of a bacterium from commensal to pathogen under certain conditions. While EM images reveal vesicles budding from the bacterial surface, the presence of cytoplasmic proteins and genomic DNA within the OMVs indicate that explosive cell lysis is an additional mechanism of biogenesis for these OMVs along with outer membrane blebbing. This research encourages future work on characterizing membrane vesicles produced by commensal bacterial and investigating their role in cell to cell communication.
外膜囊泡 (OMVs) 是革兰氏阴性细菌释放的膜封闭的球形实体，对于细菌在应激条件下的生存至关重要。已经有许多关于革兰氏阴性致病性细菌释放的 OMVs 的研究，但对共生微生物产生的 OMVs 的功能和特性的理解仍然缺乏。阴沟肠杆菌是人类肠道微生物组中的革兰氏阴性共生菌，但该菌也可以作为机会性病原体。了解细菌-细菌或细菌-宿主之间的 OMV 介导的通讯途径对于确定共生菌在肠道中的生物学功能以及区分良性和毒性特征至关重要。在这项研究中，我们描述了阴沟肠杆菌 OMVs 的蛋白质组，这些 OMVs 的大小范围为 20-300nm。蛋白质组分析显示存在膜结合蛋白，包括转运蛋白、受体、信号分子和蛋白通道。物理和蛋白质组分析还表明，该细菌使用两种机制产生 OMVs。这项研究是少数对共生变形菌产生的 OMVs 的蛋白质组图谱进行描述的研究之一，也是首次报道阴沟肠杆菌产生的 OMVs。
这项研究优先强调了理解人类共生菌阴沟肠杆菌囊泡蛋白质组的重要性。我们首次证明革兰氏阴性细菌阴沟肠杆菌 ATCC 13047 产生外膜囊泡 (OMVs)。蛋白质组分析显示这些囊泡中富含膜结合蛋白。了解 OMVs 的货物蛋白将有助于探索这些囊泡在人类微生物组中的生理和功能作用，以及它们如何在某些条件下帮助细菌从共生菌转变为病原体。虽然 EM 图像显示囊泡从细菌表面出芽，但细胞质蛋白和基因组 DNA 存在于 OMVs 中表明，对于这些 OMVs 来说，除了外膜起泡之外，细胞的爆炸裂解也是生物发生的另一种机制。这项研究鼓励未来对共生细菌产生的膜囊泡进行表征，并研究它们在细胞间通讯中的作用。
