A dynamic, ring-forming MucB / RseB-like protein influences spore shape in Bacillus subtilis.
A dynamic, ring-forming MucB / RseB-like protein influences spore shape in Bacillus subtilis.
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DOI：
10.1371/journal.pgen.1009246
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发表时间：
2020-12
期刊：
影响因子：
4.5
通讯作者：
Rodrigues CDA
中科院分区：
文献类型：
--
作者：
Luhur J;Chan H;Kachappilly B;Mohamed A;Morlot C;Awad M;Lyras D;Taib N;Gribaldo S;Rudner DZ;Rodrigues CDA
有机体如何发育成特定的形状是生物学的一个中心问题。细菌形状的维持与细胞包膜的组装和重塑有关。在内生孢子形成细菌中，前孢子室（前孢子）经历形态学变化，导致孢子具有确定的形状，具有复杂的多层细胞包膜。然而，控制孢子形状的机制仍然知之甚少。在这里，使用荧光显微镜，定量图像分析，分子遗传学和透射电子显微镜的组合，我们表明，SsdC（以前的YdcC），一个特征不佳的新成员的MucB / RseB家族的蛋白质结合脂多糖在diderm细菌，影响孢子形状的单胚层枯草芽孢杆菌。缺乏SsdC的产孢细胞不能采用野生型前孢子的典型长方形形状，而是更圆。二维和三维荧光显微镜表明，SsdC形成一个不连续的，动态的环状结构在母细胞的外周膜，靠近母细胞近极的前孢子。合成孢子形成筛选鉴定了ssdC和孢子衣组装中涉及的基因之间的遗传关系。这些突变体的表型表征表明，孢子的形状，和SsdC定位，取决于外套基底层蛋白SpoVM和SpoIVA，包裹蛋白SpoVID和内外壳蛋白SafA。重要的是，我们发现ΔssdC突变体产生具有异常外观皮层的孢子，并且在突变体中消除皮层合成在很大程度上抑制了其形状缺陷。因此，SsdC似乎在孢子皮层的正确组装中发挥作用，通过连接到孢子衣。总的来说，我们的数据表明功能多样性的MucB / RseB蛋白结构域之间的双胚层和单胚层细菌和确定SsdC作为一个重要因素孢子形状的发展。细胞形状是与细胞功能和环境适应相关的重要细胞属性。细菌内生孢子是地球上最坚韧的细胞类型之一，具有明确的形状和复杂的，高抗性的多层细胞包膜。虽然几十年的研究都集中在定义的组成和组装的多层孢子包膜，很少有人知道这些层如何有助于孢子的形状。在这里，我们确定了SsdC，一个特征不佳的新成员的MucB / RseB家族的蛋白质结合脂多糖在diderm细菌。我们表明，SsdC是一个重要的因素，孢子形状的发展在单胚层，模式生物枯草芽孢杆菌。我们的数据表明，SsdC影响组装的孢子皮层，通过连接到孢子外套，通过形成一个有趣的，动态的环状结构相邻的发展孢子。此外，我们的SsdC的鉴定表明双胚层和单胚层细菌之间的MucB /RseB蛋白结构域的进化多样化。
How organisms develop into specific shapes is a central question in biology. The maintenance of bacterial shape is connected to the assembly and remodelling of the cell envelope. In endospore-forming bacteria, the pre-spore compartment (the forespore) undergoes morphological changes that result in a spore of defined shape, with a complex, multi-layered cell envelope. However, the mechanisms that govern spore shape remain poorly understood. Here, using a combination of fluorescence microscopy, quantitative image analysis, molecular genetics and transmission electron microscopy, we show that SsdC (formerly YdcC), a poorly-characterized new member of the MucB / RseB family of proteins that bind lipopolysaccharide in diderm bacteria, influences spore shape in the monoderm Bacillus subtilis. Sporulating cells lacking SsdC fail to adopt the typical oblong shape of wild-type forespores and are instead rounder. 2D and 3D-fluorescence microscopy suggest that SsdC forms a discontinuous, dynamic ring-like structure in the peripheral membrane of the mother cell, near the mother cell proximal pole of the forespore. A synthetic sporulation screen identified genetic relationships between ssdC and genes involved in the assembly of the spore coat. Phenotypic characterization of these mutants revealed that spore shape, and SsdC localization, depend on the coat basement layer proteins SpoVM and SpoIVA, the encasement protein SpoVID and the inner coat protein SafA. Importantly, we found that the ΔssdC mutant produces spores with an abnormal-looking cortex, and abolishing cortex synthesis in the mutant largely suppresses its shape defects. Thus, SsdC appears to play a role in the proper assembly of the spore cortex, through connections to the spore coat. Collectively, our data suggest functional diversification of the MucB / RseB protein domain between diderm and monoderm bacteria and identify SsdC as an important factor in spore shape development. Cell shape is an important cellular attribute linked to cellular function and environmental adaptation. Bacterial endospores are one of the toughest cell types on Earth, with a defined shape and complex, highly-resistant, multi-layered cell envelope. Although decades of research have focused on defining the composition and assembly of the multi-layered spore envelope, little is known about how these layers contribute to spore shape. Here, we identify SsdC, a poorly-characterized new member of the MucB / RseB family of proteins that bind lipopolysaccharide in diderm bacteria. We show that SsdC is an important factor in spore shape development in the monoderm, model organism Bacillus subtilis. Our data suggest that SsdC influences the assembly of the spore cortex, through connections to the spore coat, by forming an intriguing, dynamic ring-like structure adjacent to the developing spore. Furthermore, our identification of SsdC suggests evolutionary diversification of the MucB /RseB protein domain between diderm and monoderm bacteria.
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