Gauglitz Julia M, Inomura Keisuke, Bittremieux Wout, Moran Dawn M, McIlvin Matthew R, Saito Mak A
Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution (WHOI), Woods Hole, MA, USA.
Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA.
bioRxiv. 2025 Jul 11:2025.07.11.664471. doi: 10.1101/2025.07.11.664471.
Marine diazotrophic cyanobacteria play a crucial role in oceanic nitrogen cycling, supporting primary production and ecosystem balance. WH8501 exemplifies this ability by temporally separating photosynthesis and diazotrophy to sustain metabolism. To investigate the regulatory mechanisms underlying this process, we employed LC/MS-MS proteomics in a diel culturing experiment, revealing tightly coordinated protein abundance patterns. Our findings showed a sophisticated temporal regulation of metabolic processes categorized within six distinct protein abundance clusters: (1) nitrogen fixation and amino acid biosynthesis proteins peaked during the night, while (2) glycogen metabolism and dark reactions of photosynthesis were most abundant during the night and day-night transition, likely supporting carbon consumption and energy production. Midday (3 and 4) was dominated by proteins related to photosynthesis, cellular division, and lipid synthesis, whereas late-day peaks (5) in peptide biosynthesis may facilitate nitrogenase complex formation. Notably, the day-night transition (6) exhibited fine-tuned coordination of nitrogenase assembly, with FeS cluster proteins preceding peak nitrogenase iron protein abundance, implying a temporally ordered sequence for functional enzyme formation. Within these categories, sharp temporal patterns emerged in iron trafficking to heme and iron cluster biosynthetic systems, consistent with the need to maintain tight control of iron distribution to metalloproteins at each temporal transition. These results highlight the intricate diel regulation that enables to balance nitrogen fixation and photosynthesis within a single cell. The observed coordination supports the existence of a complex regulatory system ensuring optimal metabolic performance, reinforcing the critical role of temporal control in sustaining these globally significant biological processes.
海洋固氮蓝细菌在海洋氮循环中发挥着关键作用，支持初级生产和生态系统平衡。WH8501通过在时间上分离光合作用和固氮作用以维持新陈代谢，例证了这种能力。为了研究这一过程背后的调控机制，我们在昼夜培养实验中采用了液相色谱/串联质谱蛋白质组学技术，揭示了紧密协调的蛋白质丰度模式。我们的研究结果表明，代谢过程存在复杂的时间调控，可分为六个不同的蛋白质丰度簇：（1）固氮和氨基酸生物合成蛋白在夜间达到峰值，而（2）糖原代谢和光合作用的暗反应在夜间和昼夜交替期间最为丰富，可能支持碳消耗和能量产生。中午（3和4）主要是与光合作用、细胞分裂和脂质合成相关的蛋白质，而肽生物合成中的傍晚峰值（5）可能有助于固氮酶复合物的形成。值得注意的是，昼夜交替（6）表现出固氮酶组装的精细协调，铁硫簇蛋白先于固氮酶铁蛋白丰度达到峰值，这意味着功能酶形成存在时间上有序的序列。在这些类别中，铁向血红素和铁簇生物合成系统的转运出现了明显的时间模式，这与在每个时间转换时保持对金属蛋白中铁分布的严格控制的需求一致。这些结果突出了复杂的昼夜调控，使单细胞能够平衡固氮和光合作用。观察到的协调支持了一个复杂调控系统的存在，该系统确保了最佳的代谢性能，强化了时间控制在维持这些全球重要生物过程中的关键作用。
