The Origin of Rod Shape in Bacteria

生物学中一个有待理解的基本问题是细胞形状是如何遗传的 编码和酶促生成。球体和杆状是最常见的形状之一，由 有墙的细菌。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 通过二次分裂(分裂)繁殖，两个子细胞的形状已经由它们的 母细胞。因此，很难用健康的细菌细胞来探索细胞形状的起源。拿走 粘球菌萌发过程中球状-杆状形态转变的优势 我们建议探索杆状细胞产生和维持的潜在机制 形状。黄曲霉的细胞在不同生活期的杆状和球状之间来回变化。棒子- 成形的营养细胞彻底降解它们的壁并收缩成大小均匀的球形细胞，然后 成熟成孢子。与芽孢杆菌的内孢子形成不同，整个黄曲霉细胞转化为孢子。 当黄花草的孢子萌发时，细胞在没有预先存在的情况下重建它们的壁和重建杆状 模板。这种独特的形态转变提供了一个难得的机会来观察从头开始的细胞壁 合成(CWS)和细菌形态发生。为了了解微囊藻的形态发生机制。 我们提出了三个具体的目标。首先，为了揭示新生CWS在萌发过程中的机制， 我们将检验这样的假设，即建立杆状突起需要一种明确的细胞壁生长模式 形状。第二，阐明MreB细胞骨架支持杆状结构的机制。 萌发，我们将检验MreB通过引导CWS的运动来决定杆形的假设 机械设备。第三，揭示了细胞极性对萌发过程中CWS和棒形的调节机制 孢子，我们将检验这样的假设，即细胞极性的建立是球状到杆状的必要的 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 将揭示形态发生的基本机制，这是在其他地方很难研究的 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.