Suzuki Kana, Nakane Daisuke, Mizutani Masaki, Nishizaka Takayuki
Department of Physics, Gakushuin University, Tokyo 171-8588, Japan.
Department of Engineering Science, Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo 182-8585, Japan.
Biophys Physicobiol. 2025 Feb 26;22(1):e220006. doi: 10.2142/biophysico.bppb-v22.0006. eCollection 2025.
The gliding motility of bacteria is not linear but somehow exhibits a curved trajectory. This general observation is explained by the helical structure of protein tracks (Nakane et al., 2013) or the asymmetric array of gliding machineries (Morio et al., 2016), but these interpretations have not been directly examined. Here, we introduced a simple assumption: the gliding trajectory of is guided by the cell shape. To test this idea, the intensity profile of a bacterium, , was analyzed and reconstructed at the single-cell level from images captured under a highly stable dark-field microscope, which minimized the mechanical drift and noise during sequential image recording. The raw image with the size of ~1 μm, which is about four times larger than the diffraction limit of visible light, was successfully fitted by double Gaussians to quantitatively determine the curved configuration of its shape. By comparing the shape and curvature of a gliding motility, we found that the protruded portion of correlated with, or possibly guided, its gliding direction. Considering the balance between decomposed gliding force and torque as a drag, a simple and general model that explains the curved trajectory of biomolecules under a low Reynolds number is proposed.
细菌的滑动运动并非直线运动，而是以某种方式呈现出弯曲的轨迹。这一普遍观察结果可由蛋白质轨道的螺旋结构（中根等人，2013年）或滑动机制的不对称排列（森尾等人，2016年）来解释，但这些解释尚未得到直接验证。在此，我们提出一个简单的假设：细菌的滑动轨迹受细胞形状引导。为验证这一想法，我们在高度稳定的暗场显微镜下从捕获的图像中对单个细胞水平的细菌强度分布进行了分析和重建，该显微镜在连续图像记录过程中最大限度地减少了机械漂移和噪声。大小约为1μm（约为可见光衍射极限的四倍）的原始图像成功地用双高斯函数拟合，以定量确定其形状的弯曲形态。通过比较滑动运动的形状和曲率，我们发现细菌的突出部分与其滑动方向相关，或者可能引导其滑动方向。考虑到分解的滑动力和扭矩之间的平衡作为一种阻力，我们提出了一个简单而通用的模型，用于解释低雷诺数下生物分子的弯曲轨迹。
