Physics of Living Matter, Department of Physics and Materials Science, University of Luxembourg, 162A, Avenue de la Faïencerie, 1511 Luxembourg City, Luxembourg.
Swiss Nanoscience lnstitute, University of Basel, 82, Klingelbergslrasse, 4056 Basel, Switzerland.
Sci Adv. 2022 Nov 4;8(44):eabn6005. doi: 10.1126/sciadv.abn6005.
Nutrient availability, along with light and temperature, drives marine primary production. The ability to migrate vertically, a critical trait of motile phytoplankton, allows species to optimize nutrient uptake, storage, and growth. However, this traditional view discounts the possibility that migration in nutrient-limited waters may be actively modulated by the emergence of energy-storing organelles. Here, we report that bloom-forming raphidophytes harness energy-storing cytoplasmic lipid droplets (LDs) to biomechanically regulate vertical migration in nutrient-limited settings. LDs grow and translocate directionally within the cytoplasm, steering strain-specific shifts in the speed, trajectory, and stability of swimming cells. Nutrient reincorporation restores their swimming traits, mediated by an active reconfiguration of LD size and coordinates. A mathematical model of cell mechanics establishes the mechanistic coupling between intracellular changes and emergent migratory behavior. Amenable to the associated photophysiology, LD-governed behavioral shift highlights an exquisite microbial strategy toward niche expansion and resource optimization in nutrient-limited oceans.
营养物质的可利用性，以及光照和温度，共同推动了海洋初级生产力。垂直迁移的能力，这是运动浮游植物的一个关键特征，使物种能够优化营养物质的吸收、储存和生长。然而，这种传统观点忽略了一个可能性，即在营养有限的水域中，迁移可能会被储存能量的细胞器的出现而主动调节。在这里，我们报告说，形成水华的鞭毛藻类利用储存能量的细胞质脂滴（LD）来在营养有限的环境中通过生物力学调节垂直迁移。LD 在细胞质内生长并定向迁移，引导特定菌株的游动细胞的速度、轨迹和稳定性发生变化。通过主动调整 LD 的大小和坐标，重新整合营养物质可以恢复其游动特性。细胞力学的数学模型确立了细胞内变化和新兴迁移行为之间的力学耦合。这种受相关光生理控制的行为转变凸显了微生物在营养有限的海洋中扩展生态位和优化资源的一种精细策略。
