Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
MaIAGE, INRA, Université Paris-Saclay, Jouy-en-Josas F78350, France.
Nat Commun. 2017 Jun 7;8:15370. doi: 10.1038/ncomms15370.
How cells control their shape and size is a long-standing question in cell biology. Many rod-shaped bacteria elongate their sidewalls by the action of cell wall synthesizing machineries that are associated to actin-like MreB cortical patches. However, little is known about how elongation is regulated to enable varied growth rates and sizes. Here we use total internal reflection fluorescence microscopy and single-particle tracking to visualize MreB isoforms, as a proxy for cell wall synthesis, in Bacillus subtilis and Escherichia coli cells growing in different media and during nutrient upshift. We find that these two model organisms appear to use orthogonal strategies to adapt to growth regime variations: B. subtilis regulates MreB patch speed, while E. coli may mainly regulate the production capacity of MreB-associated cell wall machineries. We present numerical models that link MreB-mediated sidewall synthesis and cell elongation, and argue that the distinct regulatory mechanism employed might reflect the different cell wall integrity constraints in Gram-positive and Gram-negative bacteria.
细胞如何控制自身的形状和大小是细胞生物学中的一个长期存在的问题。许多杆状细菌通过与肌动蛋白样 MreB 皮质斑相关的细胞壁合成机制来拉长其细胞壁。然而，对于如何调节伸长以实现不同的生长速度和大小，人们知之甚少。在这里，我们使用全内反射荧光显微镜和单粒子跟踪技术，可视化枯草芽孢杆菌和大肠杆菌细胞中作为细胞壁合成替代物的 MreB 同工型，这些细胞在不同的培养基中生长，并在营养物质增加时生长。我们发现，这两种模式生物似乎使用正交策略来适应生长模式的变化：枯草芽孢杆菌调节 MreB 斑的速度，而大肠杆菌可能主要调节与 MreB 相关的细胞壁机制的产生能力。我们提出了将 MreB 介导的侧壁合成与细胞伸长联系起来的数值模型，并认为所采用的不同调节机制可能反映了革兰氏阳性和革兰氏阴性细菌细胞壁完整性约束的不同。
