Circadian clocks create a 24-hour temporal structure, which allows organisms to occupy a niche formed by time rather than space. They are pervasive throughout nature, yet they remain unexpectedly unexplored and uncharacterized in nonphotosynthetic bacteria. Here, we identify in Bacillus subtilis circadian rhythms sharing the canonical properties of circadian clocks: free-running period, entrainment, and temperature compensation. We show that gene expression in B. subtilis can be synchronized in 24-hour light or temperature cycles and exhibit phase-specific characteristics of entrainment. Upon release to constant dark and temperature conditions, bacterial biofilm populations have temperature-compensated free-running oscillations with a period close to 24 hours. Our work opens the field of circadian clocks in the free-living, nonphotosynthetic prokaryotes, bringing considerable potential for impact upon biomedicine, ecology, and industrial processes.

昼夜节律时钟创建了 24 小时的时间结构，使生物体能够占据由时间而不是空间形成的生态位。它们在自然界中普遍存在，但出乎意料的是，它们在非光合细菌中仍未被探索和表征。在这里，我们在枯草芽孢杆菌中识别出具有生物钟典型特性的昼夜节律：自由运行周期、夹带和温度补偿。我们发现枯草芽孢杆菌中的基因表达可以在 24 小时光或温度循环中同步，并表现出阶段特异性的夹带特征。当释放到恒定的黑暗和温度条件下时，细菌生物膜群体会进行温度补偿的自由振荡，周期接近 24 小时。我们的工作开辟了自由生活、非光合作用原核生物的生物钟领域，为生物医学、生态和工业过程带来了巨大的影响潜力。