Physics Department and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel.
Langmuir. 2012 Sep 11;28(36):12941-7. doi: 10.1021/la302056j. Epub 2012 Aug 27.
We employ real-time three-dimensional confocal microscopy to follow the Brownian motion of a fixed helically shaped Leptospira interrogans (LI) bacterium. We extract from our measurements the translational and the rotational diffusion coefficients of this bacterium. A simple theoretical model is suggested, perfectly reproducing the experimental diffusion coefficients, with no tunable parameters. An older theoretical model, where edge effects are neglected, dramatically underestimates the observed rates of translation. Interestingly, the coiling of LI increases its rotational diffusion coefficient by a factor of 5, compared to a (hypothetical) rectified bacterium of the same contour length. Moreover, the translational diffusion coefficients would have decreased by a factor of ~1.5, if LI were rectified. This suggests that the spiral shape of the spirochaete bacteria, in addition to being employed for their active twisting motion, may also increase the ability of these bacteria to explore the surrounding fluid by passive Brownian diffusion.
我们采用实时三维共聚焦显微镜来追踪固定的螺旋形钩端螺旋体（LI）细菌的布朗运动。我们从测量中提取出该细菌的平移和旋转扩散系数。提出了一个简单的理论模型，该模型可以完美地再现实验扩散系数，且没有可调参数。一个忽略边缘效应的旧理论模型，大大低估了观察到的翻译速率。有趣的是，与相同轮廓长度的（假设）校正细菌相比，LI 的螺旋卷曲将其旋转扩散系数增加了 5 倍。此外，如果 LI 被校正，其平移扩散系数将减少约 1.5 倍。这表明，除了用于主动扭转运动之外，螺旋体细菌的螺旋形状还可能通过被动布朗扩散增加这些细菌在周围流体中探索的能力。
