近日，科学家在《物理评论快报》上撰文称，发现了首个由微生物构成的“活晶体”。这种微生物（Thiovulum majus）是目前已知的游泳速度最快的细菌之一。这些细菌生活在盐沼泥泞的底部，能通过氧化硫化物产生能量。

研究人员发现，当这种细菌撞击容器的边缘时，它们会沿着其表面移动，最终集合成整齐的2D形态。通过其旋转鞭毛涌动，该微生物能形成龙卷风似的流动，这能拉近附近的细菌，使其排列成晶体状块。

然而，大部分晶体是惰性结构，但多亏每个细菌施加给邻居的作用力，这些晶体能随着时间流逝重新排列和旋转。但该研究负责人、美国洛克菲勒大学的Alexander Petroff表示，科学家尚不清楚这些细菌在自然环境中能否形成此类晶体。（来源：中国科学报 张章）

Fast-moving bacteria self-organize into active two-dimensional crystals of rotating cells

Abstract  We investigate a new form of collective dynamics displayed by Thiovulum majus, one of the fastest-swimming bacteria known. Cells spontaneously organize on a surface into a visually-striking two-dimensional hexagonal lattice of rotating cells. As each constituent cell rotates its flagella, it creates a tornado-like flow that pulls neighboring cells towards and around it. As cells rotate against their neighbors, they exert forces on one-another, causing the crystal to rotate and cells to reorganize. We show how these dynamics arises from hydrodynamic and steric interactions between cells. We derive the equations of motion for an crystal, show that this model explains several aspects of the observed dynamics, and discuss the stability of these active crystals.

原文链接：http://journals.aps.org/prl/accepted/0b07eYacMbe1103df8d546f575402cb327b459471