We investigate through simulations the phenomena of magnetoreception to enable an understanding of the minimum requirements of a fail-safe mechanism, operational at the cellular level, to sense a weak magnetic field at ambient temperature in a biologically active environment. To do this, we use magnetotactic bacteria (MTB) as our model system. The magnetic field sensing ability of these bacteria is due to the presence of magnetosomes, which are internal membrane-bound organelles that contain an iron-based magnetic mineral crystal. These magnetosomes are usually found arranged in a chain aligned with the long axis of the bacterial body. This arrangement yields an overall magnetic dipole moment to the bacterial cell. To simulate this orientation process, we set up a rotational Langevin stochastic differential equation and solve it repeatedly over appropriate time steps for isolated spherical shaped MTB as well as for a more realistic model of spheroidal MTB with flagella. The orientation process appears to depend on shape parameters with spheroidal MTB showing a slower response time compared to spherical MTB. Further, our simulation also reveals that the alignment to the external magnetic field is more robust for an MTB when compared to single magnetosome. For the simulation involving magnetosomes, we include an extra torque that arises from the twisting of an attachment tether and enhance the viscosity of the surrounding medium to mimic intracellular conditions in the governing Langevin equation. The response time of alignment is found to be substantially reduced when one includes a dipole interaction term with a neighboring magnetosome and the alignment becomes less robust with increase in inter dipole distance. The alignment process can thereby be said to be very sensitively dependent on the distance between magnetosomes. Simulating the process of alignment between two neighboring magnetosomes, both in the absence and presence of an ambient magnetic field, we conclude that alignment between these dipoles at the distances typical in an MTB is highly probable and it would be the locked unit that responds to changes in the external magnetic field.

我们通过模拟研究磁感受现象，以了解在细胞水平上运行的故障安全机制的最低要求，以在生物活跃环境中感知环境温度下的弱磁场。为此，我们使用趋磁细菌 (MTB) 作为我们的模型系统。这些细菌的磁场感应能力是由于磁小体的存在，磁小体是内部膜结合的细胞器，含有铁基磁性矿物晶体。这些磁小体通常排列成与细菌体长轴对齐的链。这种布置对细菌细胞产生了整体磁偶极矩。为了模拟这种定向过程，我们建立了一个旋转的朗之万随机微分方程，并在适当的时间步长上对孤立的球形 MTB 以及更现实的带有鞭毛的球形 MTB 模型进行求解。定向过程似乎取决于形状参数，与球形 MTB 相比，球形 MTB 显示出较慢的响应时间。此外，我们的模拟还表明，与单个磁小体相比，MTB 与外部磁场的对齐更加稳健。对于涉及磁小体的模拟，我们包括一个额外的扭矩，该扭矩由连接系绳的扭曲产生，并增强周围介质的粘度以模拟控制朗之万方程中的细胞内条件。当一个包含与相邻磁小体的偶极相互作用项并且随着偶极间距离的增加对齐变得不那么稳健时，发现对齐的响应时间显着减少。因此，可以说对齐过程非常敏感地依赖于磁小体之间的距离。模拟两个相邻磁小体之间的对齐过程，无论是在不存在和存在环境磁场的情况下，我们得出结论，这些偶极子在 MTB 中典型距离处对齐的可能性很高，它将是响应变化的锁定单元在外磁场中。因此，可以说对齐过程非常敏感地依赖于磁小体之间的距离。模拟两个相邻磁小体之间的对齐过程，无论是在不存在和存在环境磁场的情况下，我们得出结论，这些偶极子在 MTB 中典型距离处对齐的可能性很高，它将是响应变化的锁定单元在外磁场中。因此，可以说对齐过程非常敏感地依赖于磁小体之间的距离。模拟两个相邻磁小体之间的对齐过程，无论是在不存在和存在环境磁场的情况下，我们得出结论，这些偶极子在 MTB 中典型距离处对齐的可能性很高，它将是响应变化的锁定单元在外磁场中。