Deschoenmaeker Frédéric, Facchini Raphaël, Leroy Baptiste, Badri Hanène, Zhang C-C, Wattiez Ruddy
Department of Proteomics and Microbiology, Research Institute for Biosciences, University of Mons, Place du Parc 20, B-7000 Mons, Belgium.
Expert Group for Molecular and Cellular Biology MCB, Belgian Nuclear Research Center SCK.CEN, B-2400 Mol, Belgium.
Microbiology (Reading). 2014 Jun;160(Pt 6):1224-1236. doi: 10.1099/mic.0.074641-0. Epub 2014 Mar 19.
Cyanobacteria are photosynthetic prokaryotes that play a crucial role in the Earth's nitrogen and carbon cycles. Nitrogen availability is one of the most important factors in cyanobacterial growth. Interestingly, filamentous non-diazotrophic cyanobacteria, such as Arthrospira sp. PCC 8005, have developed survival strategies that enable them to adapt to nitrogen deprivation. Metabolic studies recently demonstrated a substantial synthesis and accumulation of glycogen derived from amino acids during nitrogen starvation. Nevertheless, the regulatory mechanism of this adaptation is poorly understood. To the best of our knowledge, this study is the first proteomic and cellular analysis of Arthrospira sp. PCC 8005 under nitrogen depletion. Label-free differential proteomic analysis indicated the global carbon and nitrogen reprogramming of the cells during nitrogen depletion as characterized by an upregulation of glycogen synthesis and the use of endogenous nitrogen sources. The degradation of proteins and cyanophycin provided endogenous nitrogen when exogenous nitrogen was limited. Moreover, formamides, cyanates and urea were also potential endogenous nitrogen sources. The transporters of some amino acids and alternative nitrogen sources such as ammonium permease 1 were induced under nitrogen depletion. Intriguingly, although Arthrospira is a non-diazotrophic cyanobacterium, we observed the upregulation of HetR and HglK proteins, which are involved in heterocyst differentiation. Moreover, after a long period without nitrate, only a few highly fluorescent cells in each trichome were observed, and they might be involved in the long-term survival mechanism of this non-diazotrophic cyanobacterium under nitrogen deprivation.
蓝细菌是光合原核生物，在地球的氮和碳循环中发挥着关键作用。氮的可利用性是蓝细菌生长的最重要因素之一。有趣的是，丝状非固氮蓝细菌，如节旋藻属PCC 8005，已经发展出了使其能够适应氮缺乏的生存策略。代谢研究最近表明，在氮饥饿期间，氨基酸来源的糖原大量合成并积累。然而，这种适应性的调控机制仍知之甚少。据我们所知，本研究是对节旋藻属PCC 8005在氮耗尽条件下的首次蛋白质组学和细胞分析。无标记差异蛋白质组学分析表明，在氮耗尽期间细胞的全局碳和氮重新编程，其特征是糖原合成上调以及内源性氮源的利用。当外源氮有限时，蛋白质和藻青素的降解提供了内源性氮。此外，甲酰胺、氰酸盐和尿素也是潜在的内源性氮源。一些氨基酸和替代氮源的转运蛋白，如铵通透酶1，在氮耗尽时被诱导。有趣的是，尽管节旋藻是一种非固氮蓝细菌，但我们观察到参与异形胞分化的HetR和HglK蛋白上调。此外，在长时间没有硝酸盐后，每个藻丝中仅观察到少数高荧光细胞，它们可能参与了这种非固氮蓝细菌在氮缺乏条件下的长期生存机制。
