Research Starter Grant: Cellular Biomechanics of Bacillus subtilis

许多细菌都是圆柱形的，尽管考虑到细胞内的膨压，对细菌细胞的简单看法表明所有细菌的形状都应该是大致球形的。 杆状细菌是如何形成并保持其形态的？ 这个问题将使用物理分析和数学建模来解决，考虑到已知的细菌生物化学和组织。细胞壁主要由肽聚糖的聚合物网组成，其将细胞内部与细胞外部分开并提供结构刚性。直接在肽聚糖内的是双层膜。细胞维持膨压，使得细胞内部处于比细胞外部更高的压力。因此，细胞形态的一个简单图像是肽聚糖形成了一个弹性层，它包围了这个压力差，就像一个气球。然而，这并不能解释细胞的圆柱形，因为压力差会驱使肽聚糖层朝向更球形的形式。另一个实验室最近的实验表明，位于细胞膜内部的肌动蛋白样聚合物蛋白可能在某些细菌（如枯草芽孢杆菌）中保持圆柱形方面发挥关键作用。这些实验也表明了一种分子机制，可以驱动在B的粗纤维中观察到的超螺旋行为。枯草杆菌和许多其它丝状圆柱形细菌。本研究项目将探索位于细胞膜或其附近的螺旋聚合物蛋白与细胞壁弹性之间的联系，以探索这些蛋白在维持细胞形态方面发挥的作用，研究它们是否可能是超螺旋的分子原因，并建议进一步的实验来验证这些假设。这是一个研究启动补助金，授予NSF博士后研究员谁已经接受了终身职位的轨道位置在一个合格的机构，如NSF 99-142中所述。 Wolgemuth博士将积极整合研究和教育，并通过招募生物学研究生来促进跨学科培训。

Many bacteria are cylindrical, although a simplistic view of the bacterial cell, taking into account the turgor pressure within the cell, would suggest that all bacterial should be roughly spherical in shape. How do rod-shaped bacteria achieve and maintain their morphology? This question will be addressed using physical analysis and mathematical modelling, taking into acount what is known of bacterial biochemistry and organization. The cell wall is composed predominantly of a polymer mesh of peptidoglycan that separates the inside of the cell from the outside of the cell and provides structural rigidity. Directly inside the peptidoglycan is a bilayer membrane. The cell maintains a turgor pressure such that the inside of the cell is at a higher pressure than outside the cell. Therefore, a simple picture of cell morphology would be that the peptidoglycan forms an elastic layer that encloses this pressure difference, much like a balloon. This, however, does not account for the cylindrical shape of the cell, as the pressure difference would drive the peptidoglycan layer toward a more spherical form. Recent experiments from another laboratory suggest that actin-like polymer proteins located just inside the cell membrane may play a crucial role in maintaining cylindrical form in some bacteria, such as Bacillus subtilis. Those experiments also suggest a molecular mechanism that could drive the supercoiling behavior that has been observed in macrofibers of B. subtilis and a number of other filamentous cylindrical bacteria. This research project will explore the connection between helical polymer proteins located at or near the cell membrane and the elasticity of the cell wall in order to probe the role these proteins play in maintaining cellular form, examine whether they could be the molecular cause of supercoiling, and suggest further experiments to test these hypotheses.Broader Impacts: This is a Research Starter Grant, awarded to an NSF Postdoctoral Fellow who has accepted a tenure-track position at an eligible institution, as described in NSF 99-142. Dr. Wolgemuth will actively integrate research and education and foster cross-disciplinary training by recruiting a biology graduate student to work on this project.