The bloom and bust patterns of microalgae in aquatic systems contribute massively to global biogeochemical cycles. The decline of algal blooms is mainly caused by nutrient limitation resulting in cell death, the arrest of cell division and the aging of surviving cells. Nutrient intake can re-initiate proliferation, but the processes involved are poorly understood. Here we characterize how the bloom-forming diatom Coscinodiscus radiatus recovers from starvation after nutrient influx. Rejuvenation is mediated by extracellular vesicles that shuttle reactive oxygen species, oxylipins and other harmful metabolites out of the old cells, thereby re-enabling their proliferation. By administering nutrient pulses to aged cells and metabolomic monitoring of the response, we show that regulated pathways are centred around the methionine cycle in C. radiatus. Co-incubation experiments show that bacteria mediate aging processes and trigger vesicle production using chemical signalling. This work opens new perspectives on cellular aging and rejuvenation in complex microbial communities.

水生系统中微藻的盛衰模式对全球生物地球化学循环做出了巨大贡献。藻华减少主要是由于营养限制导致细胞死亡、细胞分裂停滞和存活细胞老化造成的。营养摄入可以重新启动增殖，但所涉及的过程却知之甚少。在这里，我们描述了形成水华的硅藻Coscinodiscus radiatus在养分流入后如何从饥饿中恢复。再生是由细胞外囊泡介导的，该囊泡将活性氧、氧脂质和其他有害代谢物从旧细胞中运送出去，从而重新使其增殖。通过对衰老细胞进行营养脉冲并对反应进行代谢组学监测，我们发现辐射调节途径以蛋氨酸循环为中心。共孵化实验表明，细菌利用化学信号介导衰老过程并触发囊泡产生。这项工作为复杂微生物群落的细胞衰老和复兴开辟了新的视角。