{"title":"纤毛虫生存行为背后的简单动力学。","authors":"Takuya Ohmura, Yukinori Nishigami, Masatoshi Ichikawa","doi":"10.2142/biophysico.bppb-v19.0026","DOIUrl":null,"url":null,"abstract":"<p><p>Ciliates are swimming microorganisms in aquatic environments. Habitats where ciliates accumulate include nutrient-rich solid-liquid interfaces such as pond bottom walls and waterweed surfaces. The ciliates stay near the walls to survive. We investigated the dynamics of the near-wall behavior of ciliates. In experiments, the ciliates were made to slide on a flat wall of glass substrate. When encountering the wall, the wall-side cilia of the cells stop their motion and lose their propelling activity, which indicates that the ciliates have a mechano-sensing system for cilia beating. Based on the experimental results, we hypothesized that the ciliary thrust force that propels the cell body becomes asymmetric, and the asymmetry of the thrust force generates a head-down torque to keep the cell sliding on the wall. To prove this hypothesis, we performed numerical simulations by using a developed hydrodynamic model for swimming ciliates. The model revealed that the loss of cilia activity on the wall side physically induces a sliding motion, and the aspect ratio of the cell body and effective cilium area are critical functions for the sliding behavior on a wall. In addition, we investigated the stability of the sliding motion against an external flow. We found that ciliates slide upstream on a wall. Interestingly, the dynamics of this upstream sliding, called rheotaxis, were also explained by the identical physical conditions for no-flow sliding. Only two simple physical conditions are required to explain the dynamics of ciliate survival behavior. This review article is an extended version of the Japanese article, Fluid Dynamic Model Reveals a Mechano-sensing System Underlying the Behavior of Ciliates, published in SEIBUTSU BUTSURI Vol. 61, p. 16-19 (2021).</p>","PeriodicalId":8976,"journal":{"name":"Biophysics and Physicobiology","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2022-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/07/96/19_e190026.PMC9465405.pdf","citationCount":"0","resultStr":"{\"title\":\"Simple dynamics underlying the survival behaviors of ciliates.\",\"authors\":\"Takuya Ohmura, Yukinori Nishigami, Masatoshi Ichikawa\",\"doi\":\"10.2142/biophysico.bppb-v19.0026\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>Ciliates are swimming microorganisms in aquatic environments. 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引用次数: 0
摘要
纤毛虫是水生环境中的游动微生物。纤毛虫聚集的栖息地包括营养丰富的固液界面,如池塘底壁和水草表面。纤毛虫在墙壁附近生存。我们研究了纤毛虫近壁行为的动力学。在实验中,纤毛虫在玻璃基底的平壁上滑动。当细胞的壁侧纤毛遇到壁面时,细胞的壁侧纤毛停止运动,失去推进活动,这表明纤毛具有对纤毛跳动的机械感应系统。根据实验结果,我们假设推动细胞体的纤毛推力变得不对称,而推力的不对称产生了一个头部向下的扭矩来保持细胞在壁上滑动。为了证明这一假设,我们使用已开发的游泳纤毛虫水动力学模型进行了数值模拟。该模型表明,细胞壁纤毛活性的丧失在物理上引起了细胞壁的滑动运动,而细胞体长径比和有效纤毛面积是细胞壁滑动行为的关键函数。此外,我们研究了滑动运动对外部流动的稳定性。我们发现纤毛虫沿着墙壁向上游滑动。有趣的是,这种上游滑动的动力学称为流变性,也可以用无流滑动的相同物理条件来解释。只需要两个简单的物理条件就可以解释纤毛虫生存行为的动力学。这篇综述文章是日本文章《流体动力学模型揭示了纤毛虫行为背后的机械传感系统》的扩展版,发表于SEIBUTSU BUTSURI Vol. 61, p. 16-19(2021)。
Simple dynamics underlying the survival behaviors of ciliates.
Ciliates are swimming microorganisms in aquatic environments. Habitats where ciliates accumulate include nutrient-rich solid-liquid interfaces such as pond bottom walls and waterweed surfaces. The ciliates stay near the walls to survive. We investigated the dynamics of the near-wall behavior of ciliates. In experiments, the ciliates were made to slide on a flat wall of glass substrate. When encountering the wall, the wall-side cilia of the cells stop their motion and lose their propelling activity, which indicates that the ciliates have a mechano-sensing system for cilia beating. Based on the experimental results, we hypothesized that the ciliary thrust force that propels the cell body becomes asymmetric, and the asymmetry of the thrust force generates a head-down torque to keep the cell sliding on the wall. To prove this hypothesis, we performed numerical simulations by using a developed hydrodynamic model for swimming ciliates. The model revealed that the loss of cilia activity on the wall side physically induces a sliding motion, and the aspect ratio of the cell body and effective cilium area are critical functions for the sliding behavior on a wall. In addition, we investigated the stability of the sliding motion against an external flow. We found that ciliates slide upstream on a wall. Interestingly, the dynamics of this upstream sliding, called rheotaxis, were also explained by the identical physical conditions for no-flow sliding. Only two simple physical conditions are required to explain the dynamics of ciliate survival behavior. This review article is an extended version of the Japanese article, Fluid Dynamic Model Reveals a Mechano-sensing System Underlying the Behavior of Ciliates, published in SEIBUTSU BUTSURI Vol. 61, p. 16-19 (2021).