Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94025, USA.
Environ Microbiol. 2014 Feb;16(2):598-610. doi: 10.1111/1462-2920.12187. Epub 2013 Jul 15.
The social soil bacterium, Myxococcus xanthus, displays a variety of complex and highly coordinated behaviours, including social motility, predatory rippling and fruiting body formation. Here we show that M. xanthus cells produce a network of outer membrane extensions in the form of outer membrane vesicle chains and membrane tubes that interconnect cells. We observed peritrichous display of vesicles and vesicle chains, and increased abundance in biofilms compared with planktonic cultures. By applying a range of imaging techniques, including three-dimensional (3D) focused ion beam scanning electron microscopy, we determined these structures to range between 30 and 60 nm in width and up to 5 μm in length. Purified vesicle chains consist of typical M. xanthus lipids, fucose, mannose, N-acetylglucosamine and N-acetylgalactoseamine carbohydrates and a small set of cargo protein. The protein content includes CglB and Tgl outer membrane proteins known to be transferable between cells in a contact-dependent manner. Most significantly, the 3D organization of cells within biofilms indicates that cells are connected via an extensive network of membrane extensions that may connect cells at the level of the periplasmic space. Such a network would allow the transfer of membrane proteins and other molecules between cells, and therefore could provide a mechanism for the coordination of social activities.
土壤共生菌粘球菌（Myxococcus xanthus）表现出多种复杂且高度协调的行为，包括社会运动性、捕食性波纹以及子实体形成。在这里，我们展示了 M. xanthus 细胞以膜泡链和膜管的形式产生了一种细胞间相互连接的外膜延伸网络。我们观察到周生的膜泡和膜泡链的展示，并且在生物膜中比浮游培养物中更为丰富。通过应用一系列成像技术，包括三维（3D）聚焦离子束扫描电子显微镜，我们确定这些结构的宽度在 30 至 60nm 之间，长度可达 5μm。纯化的膜泡链由典型的 M. xanthus 脂质、岩藻糖、甘露糖、N-乙酰葡萄糖胺和 N-乙酰半乳糖胺碳水化合物以及一小部分货物蛋白组成。蛋白质含量包括 CglB 和 Tgl 外膜蛋白，已知它们可以以接触依赖的方式在细胞间传递。最重要的是，生物膜中细胞的 3D 组织表明，细胞通过广泛的膜延伸网络连接，这些网络可能在周质空间水平上连接细胞。这样的网络将允许膜蛋白和其他分子在细胞之间转移，因此可以为社会活动的协调提供一种机制。
