Mazzag B C, Zhulin I B, Mogilner A
Department of Mathematics, Humboldt State University, Arcata, California 95521, USA.
Biophys J. 2003 Dec;85(6):3558-74. doi: 10.1016/S0006-3495(03)74775-4.
Aerotaxis is a particular form of "energy taxis". It is based on a largely elusive signal transduction machinery. In aerotaxis, oxygen dissolved in water plays the role of both attractant (at moderate concentrations) and repellent (at high and low concentrations). Cells swimming from favorable oxygen concentrations into regions with unfavorable concentrations increase the frequency of reversals, turn back into the favorable domain, and become effectively trapped there. At the same time, bacteria consume oxygen, creating an oxygen gradient. This behavior leads to a pattern formation phenomenon: bacteria self-organize into a dense band at a certain distance from the air-water interface. We incorporate experimental observations of the aerotactic bacterium, Azospirillum brasilense, into a mathematical model. The model consists of a system of differential equations describing swimming bacterial cells and diffusing oxygen. The cells' frequency of reversals depends on the concentration of oxygen and its time derivative while oxygen is depleted by the bacteria. We suggest a hypothetical model of energy sensing mediated by aerotactic receptors Aer and Tsr. Computer simulations and analysis of the model equations allow comparisons of theoretical and experimental results and provide insight into the mechanisms of bacterial pattern formation and underlying signal transduction machinery. We make testable predictions about position and density of the bacterial band.
趋氧性是“能量趋化性”的一种特殊形式。它基于一种很大程度上难以捉摸的信号转导机制。在趋氧性中，溶解在水中的氧气既充当吸引剂（在适度浓度下）又充当驱避剂（在高浓度和低浓度下）。从有利氧气浓度区域游向不利浓度区域的细胞会增加反转频率，转向回到有利区域，并有效地被困在那里。与此同时，细菌消耗氧气，形成氧气梯度。这种行为导致一种模式形成现象：细菌在距气 - 水界面一定距离处自组织成一条密集带。我们将趋氧细菌巴西固氮螺菌的实验观察结果纳入一个数学模型。该模型由一组描述游动细菌细胞和扩散氧气的微分方程组成。细胞的反转频率取决于氧气浓度及其时间导数，而氧气会被细菌消耗。我们提出了一个由趋氧受体Aer和Tsr介导的能量传感假设模型。对模型方程的计算机模拟和分析能够比较理论和实验结果，并深入了解细菌模式形成的机制以及潜在的信号转导机制。我们对细菌带的位置和密度做出了可检验的预测。
