Department of Microbiology, Max Planck Institute for Marine Microbiology, Bremen, Germany.
Electron Microscopy Core Facility, EMBL Heidelberg, Heidelberg, Germany.
Appl Environ Microbiol. 2019 Sep 17;85(19). doi: 10.1128/AEM.00829-19. Print 2019 Oct 1.
Large surface-to-volume ratios provide optimal nutrient uptake conditions for small microorganisms in oligotrophic habitats. The surface area can be increased with appendages. Here, we describe chains of interconnecting vesicles protruding from cells of strain Hel3_A1_48, affiliating with spp. within the and originating from coastal free-living bacterioplankton. The chains were up to 10 μm long and had vesicles emanating from the outer membrane with a single membrane and a size of 80 to 100 nm by 50 to 80 nm. Cells extruded membrane tubes in the exponential phase, whereas vesicle chains dominated on cells in the stationary growth phase. This formation is known as pearling, a physical morphogenic process in which membrane tubes protrude from liposomes and transform into chains of interconnected vesicles. Proteomes of whole-cell membranes and of detached vesicles were dominated by outer membrane proteins, including the type IX secretion system and surface-attached peptidases, glycoside hydrolases, and endonucleases. Fluorescein-labeled laminarin stained the cells and the vesicle chains. Thus, the appendages provide binding domains and degradative enzymes on their surfaces and probably storage volume in the vesicle lumen. Both may contribute to the high abundance of these -affiliated bacteria during laminarin utilization shortly after spring algal blooms. Microorganisms produce membrane vesicles. One synthesis pathway seems to be pearling that describes the physical formation of vesicle chains from phospholipid vesicles via extended tubes. Bacteria with vesicle chains had been observed as well as bacteria with tubes, but pearling was so far not observed. Here, we report the observation of, initially, tubes and then vesicle chains during the growth of a flavobacterium, suggesting biopearling of vesicle chains. The flavobacterium is abundant during spring bacterioplankton blooms developing after algal blooms and has a special set of enzymes for laminarin, the major storage polysaccharide of microalgae. We demonstrated with fluorescently labeled laminarin that the vesicle chains bind laminarin or contain laminarin-derived compounds. Proteomic analyses revealed surface-attached degradative enzymes on the outer membrane vesicles. We conclude that the large surface area and the lumen of vesicle chains may contribute to the ecological success of this marine bacterium.
大的表面积与体积比为贫营养栖息地的小型微生物提供了最佳的养分吸收条件。可以通过附属物来增加表面积。在这里，我们描述了从属于 属的菌株 Hel3_A1_48 细胞中突出的互连泡囊链，该菌株源自沿海自由生活的细菌浮游生物。这些链长可达 10μm，泡囊从外膜突出，具有单层和 80 至 100nm×50 至 80nm 的大小。细胞在指数生长期中挤出膜管，而泡囊链则在静止生长阶段主宰细胞。这种形成被称为珍珠化，这是一种物理形态发生过程，其中膜管从脂质体中突出并转化为互连的泡囊链。全细胞膜和分离泡囊的蛋白质组主要由外膜蛋白组成，包括类型 IX 分泌系统和表面附着的肽酶、糖苷水解酶和内切酶。荧光标记的昆布多糖染色了细胞和泡囊链。因此，这些附属物在其表面提供结合域和降解酶，并可能在泡囊腔中提供储存体积。这两者都可能有助于在春季藻类大量繁殖后不久利用昆布多糖时，这些与相关的细菌大量存在。微生物会产生膜泡。一种合成途径似乎是珍珠化，它描述了通过延伸管从磷脂泡囊中形成泡囊链的物理形成。已经观察到带有泡囊链的细菌以及带有管的细菌，但迄今为止尚未观察到珍珠化。在这里，我们报告了在黄杆菌生长过程中最初观察到管，然后观察到泡囊链的观察结果，这表明泡囊链的生物珍珠化。该黄杆菌在藻类大量繁殖后形成的春季细菌浮游生物大量繁殖期间丰富，并具有用于微藻主要储存多糖昆布多糖的特殊酶组。我们用荧光标记的昆布多糖证明了泡囊链结合昆布多糖或含有昆布多糖衍生化合物。蛋白质组分析显示外膜泡囊上附着有表面降解酶。我们得出结论，泡囊链的大表面积和腔可能有助于这种海洋细菌的生态成功。
