Novel metabolic attributes of the genus cyanothece, comprising a group of unicellular nitrogen-fixing Cyanothece.
Novel metabolic attributes of the genus cyanothece, comprising a group of unicellular nitrogen-fixing Cyanothece.
复制标题
氰基属的新型代谢属性，包括一组单细胞氮固定氰基。
作者：
Bandyopadhyay A;Elvitigala T;Welsh E;Stöckel J;Liberton M;Min H;Sherman LA;Pakrasi HB
蓝杆藻属包括单细胞蓝细菌，其在形态上多样且在生态上通用。过去十年的研究已经确定该属的成员是海洋生态系统的重要组成部分，对氮和碳循环做出了重大贡献。蓝杆藻ATCC 51142是这一类群的原型成员，其系统级研究揭示了许多有趣的代谢属性。为了鉴定定义这类蓝细菌的代谢特征，对另外五种蓝丝菌菌株进行测序。蓝杆藻是一种单细胞、需氧固氮蓝藻，其固氮酶基因簇的存在和固氮能力使其成为一类独特的单细胞、需氧固氮蓝藻。蓝杆藻细胞可以在夜间创造一个缺氧的细胞内环境，允许这些产氧生物体中发生氧敏感过程。大量的碳水化合物储备在白天积累在细胞中，确保有足够的能量用于需要细胞缺氧阶段的过程。我们的研究表明，该属保持了一个塑料基因组，结合了新的代谢能力，同时保留了古老的代谢特征，这种独特的组合提供了适应各种生态和环境条件的灵活性。蓝藻属7425菌株固氮酶簇的重排及其有氧固氮能力的丧失表明，在最终失去固氮能力的蓝藻菌株中可能存在类似的机制。蓝杆藻属单细胞蓝藻在水生和陆生环境中的氮循环中具有重要作用。蓝杆藻ATCC 51142在过去十年中被广泛研究，并已成为生物能源生产的重要模式光合微生物。为了扩大我们对这一蓝藻群独特代谢能力的理解，我们分析了来自不同地理栖息地的另外五种蓝杆藻菌株的基因组序列，这些菌株表现出不同的形态和生理属性。这些菌株在有氧条件下表现出高的固氮率和产氢率。它们可以产生大量的碳水化合物，这些碳水化合物储存在大的淀粉样颗粒中，并在细胞的黑暗缺氧阶段促进能量密集型过程。一些蓝杆藻属菌株的基因组是非常独特的，因为除了一个大的环状染色体外，还有线性元件。我们的研究为这类单细胞固氮蓝藻的代谢提供了新的见解。
The genus Cyanothece comprises unicellular cyanobacteria that are morphologically diverse and ecologically versatile. Studies over the last decade have established members of this genus to be important components of the marine ecosystem, contributing significantly to the nitrogen and carbon cycle. System-level studies of Cyanothece sp. ATCC 51142, a prototypic member of this group, revealed many interesting metabolic attributes. To identify the metabolic traits that define this class of cyanobacteria, five additional Cyanothece strains were sequenced to completion. The presence of a large, contiguous nitrogenase gene cluster and the ability to carry out aerobic nitrogen fixation distinguish Cyanothece as a genus of unicellular, aerobic nitrogen-fixing cyanobacteria. Cyanothece cells can create an anoxic intracellular environment at night, allowing oxygen-sensitive processes to take place in these oxygenic organisms. Large carbohydrate reserves accumulate in the cells during the day, ensuring sufficient energy for the processes that require the anoxic phase of the cells. Our study indicates that this genus maintains a plastic genome, incorporating new metabolic capabilities while simultaneously retaining archaic metabolic traits, a unique combination which provides the flexibility to adapt to various ecological and environmental conditions. Rearrangement of the nitrogenase cluster in Cyanothece sp. strain 7425 and the concomitant loss of its aerobic nitrogen-fixing ability suggest that a similar mechanism might have been at play in cyanobacterial strains that eventually lost their nitrogen-fixing ability. The unicellular cyanobacterial genus Cyanothece has significant roles in the nitrogen cycle in aquatic and terrestrial environments. Cyanothece sp. ATCC 51142 was extensively studied over the last decade and has emerged as an important model photosynthetic microbe for bioenergy production. To expand our understanding of the distinctive metabolic capabilities of this cyanobacterial group, we analyzed the genome sequences of five additional Cyanothece strains from different geographical habitats, exhibiting diverse morphological and physiological attributes. These strains exhibit high rates of N2 fixation and H2 production under aerobic conditions. They can generate copious amounts of carbohydrates that are stored in large starch-like granules and facilitate energy-intensive processes during the dark, anoxic phase of the cells. The genomes of some Cyanothece strains are quite unique in that there are linear elements in addition to a large circular chromosome. Our study provides novel insights into the metabolism of this class of unicellular nitrogen-fixing cyanobacteria.