Development of evaluation method for bacterial motility based on the flow dynamics and the large deviation mechanics

布朗运动是纳米/微米尺度流体动力学的基本现象。另一方面，细菌的运动在本质上不同于布朗运动，但表现出一定的随机性。近年来，由于单粒子跟踪(SPT)或单分子跟踪(SMT)技术在医学、生物和材料加工等领域的重要应用，单粒子跟踪(SPT)或单分子跟踪(SMT)技术得到了迅猛发展。然而，与测量技术相比，对获得的弹道数据的分析还没有得到深入的解决。在本研究中，我们发展了基于大偏差原则的评价方法。特别是，我们已经证明了在没有粒子取向信息的情况下，可以解释长椭圆形粒子的扩散各向异性。此外，我们还表明，有限样本效应可用于表征细菌的运动性。

Brownian motion is a fundamental phenomenon of nano/micro scale fluid dynamics. On the other hand, bacterial motility is known to show some stochasticity while essentially different from Brownian motion. Recently, there have been drastic developments in the techniques of single particle tracking (SPT) or single molecule tracking (SMT) due to the importance in the medical and biological applications as well as material processing. However, the analysis of the obtained trajectory data has not been addressed intensively compared to the measurement technology. In this study, we have developed the evaluation methodology based on the large deviation principle. In particular, we have shown that it is possible to elucidate the diffusion anisotropy of a prolate particle without the information of particle orientation. Furthermore, we have shown that the finite-sample effect can be useful in the characterization of bacterial motility.