The Origin of Rod Shape in Bacteria

生物学中有待理解的一个基本问题是细胞形状是如何从遗传角度决定的 编码并酶促生成。球体和棒体是最常见的形状 有壁细菌。由肽聚糖形成的细菌细胞壁在很大程度上决定了细胞的形状。当细菌 通过二元裂变（分裂）繁殖，两个子细胞的形状已经由它们的形状决定 母细胞。因此，很难利用健康的细菌细胞来探索细胞形状的起源。服用 粘球菌萌发过程中球状到杆状形态转变的优势 xanthus，我们建议探索杆状细胞生成和维持的机制 形状。 M. xanthus 的细胞在不同的生命阶段在杆状细胞和球状细胞之间来回变化。杆- 成形的营养细胞彻底降解其壁并收缩成大小均匀的球形细胞，然后 成熟为孢子。与芽孢杆菌属物种中内生孢子的形成不同，整个 M. xanthus 细胞转化为孢子。 当 M. xanthus 的孢子萌发时，细胞会重建其细胞壁并重新形成杆状形状，而无需预先存在 模板。这种独特的形态转变为从头观察细胞壁提供了难得的机会 合成（CWS）和细菌形态发生。了解M.形态发生的机制。 xanthus，我们提出了三个具体目标。首先，揭示萌发过程中de novo CWS的机制， 我们将检验这样的假设：细胞壁生长的确定模式对于杆的建立是必需的 形状。其次，阐明MreB细胞骨架在细胞生长过程中支持杆状的机制。 发芽后，我们将检验 MreB 通过引导 CWS 的运动来确定杆形状的假设 机械。三、揭示细胞极性调控萌发过程中CWS和杆状形状的机制 孢子，我们将检验以下假设：细胞极性的建立对于球体到杆体是必要的 过渡。由于肽聚糖细胞壁在细菌中广泛保守，我们预计我们的结果 与 M. xanthus 合作将揭示形态发生的基本机制，这在其他研究中很难研究 细菌。

A fundamental question in biology that remains to be understood is how cell shapes are genetically encoded and enzymatically generated. Spheres and rods are among the most common shapes adopted by walled bacteria. The bacterial cell wall, formed by peptidoglycan, largely determines cell shape. When bacteria reproduce by binary fission (division), the shapes of the two daughter cells are already determined by their mother cell. For this reason, it is difficult to explore the origin of cell shape using healthy bacterial cells. Taking advantage of a sphere-to-rod morphological transition during the germination of the bacterium Myxococcus xanthus, we propose to explore the mechanisms underlying the generation and maintenance of rod-like cell shapes. Cells of M. xanthus change back and forth between rods and spheres at different life stages. Rod- shaped vegetative cells thoroughly degrade their walls and shrink into uniformly sized spherical cells that then mature into spores. Unlike endospore formation in Bacillus species, whole M. xanthus cells convert to spores. As the spores of M. xanthus germinate, cells rebuild their walls and reestablish rod shape without preexisting templates. This unique morphological transition provides a rare opportunity to visualize de novo cell wall synthesis (CWS) and bacterial morphogenesis. To understand the mechanism of morphogenesis in M. xanthus, we propose three specific aims. First, to reveal the mechanism of de novo CWS during germination, we will test the hypothesis that a defined pattern of cell wall growth is required for the establishment of rod shape. Second, to elucidate the mechanism by which the MreB cytoskeleton supports rod shape during germination, we will test the hypothesis that MreB determines rod shape by guiding the motion of the CWS machinery. Third, to reveal the mechanism by which cell polarity regulates CWS and rod shape in germinating spores, we will test the hypothesis that the establishment of cell polarity is necessary for the sphere-to-rod transition. Because the peptidoglycan cell wall is widely conserved among bacteria, we expect that our results with M. xanthus will reveal fundamental mechanisms of morphogenesis, which is difficult to study in other bacteria.