Magnetotactic bacteria are swimming microorganisms able to follow magnetic field lines with the help of an organelle called the magnetosome that is made of biomineralized magnetic crystals assembled in a chain. In combination with this ability, these bacteria perform active oxygen sensing to reach the oxic-anoxic transition zone, which is often located in the upper part of the sediment. From a physicist’s perspective, magnetotactic bacteria can be seen at the interface between bacterial active matter and magnetic colloids, which gives them unique properties at both the individual and collective levels. In crowded media and/or when they are submitted to external flows, their motion can be efficiently driven by magnetic fields, which leads to surprising effects. In this Colloquium, the different features of magnetotactic bacteria at are reviewed at every scale, from single cell to collective motion, from simple to complex environments, and by emphasizing the differences from other bacterial species or passive magnetic colloids. The Colloquium concludes with a discussion of perspectives on using magnetotactic bacteria in active magnetorheology.

中文翻译：

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座谈会：趋磁细菌：从鞭毛运动到集体效应

趋磁细菌是一种游动的微生物，能够在称为磁小体的细胞器的帮助下沿着磁场线移动，磁小体由组装成链的生物矿化磁性晶体组成。与这种能力相结合，这些细菌执行活性氧传感以到达含氧-缺氧过渡区，该过渡区通常位于沉积物的上部。从物理学家的角度来看，趋磁细菌可以在细菌活性物质和磁性胶体之间的界面上看到，这使得它们在个体和集体水平上都具有独特的特性。在拥挤的介质中和/或当它们受到外部流动时，它们的运动可以由磁场有效驱动，这会产生令人惊讶的效果。在本次研讨会上，从单细胞到集体运动，从简单到复杂的环境，并强调与其他细菌物种或被动磁性胶体的差异，从各个层面回顾了趋磁细菌的不同特征。研讨会最后讨论了在主动磁流变学中使用趋磁细菌的观点。