A novel thylakoid-less isolate fills a billion-year gap in the evolution of Cyanobacteria
A novel thylakoid-less isolate fills a billion-year gap in the evolution of Cyanobacteria
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DOI：
10.1016/j.cub.2021.04.042
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发表时间：
2021-07-12
期刊：
影响因子：
9.2
通讯作者：
Li, Fay-Wei
中科院分区：
文献类型：
--
作者：
Rahmatpour, Nasim;Hauser, Duncan A.;Li, Fay-Wei
蓝细菌在地球地质历史中，尤其是在大气氧含量上升过程中发挥了关键作用。然而，由于其生命之树极度不均衡，我们推断蓝细菌早期演化转变的能力受到了限制——绝大多数现存的蓝细菌多样性属于藻杆菌（或“冠群蓝细菌”），而其姊妹谱系黏杆蓝细菌类群种类稀少，仅包含两个亲缘关系密切的黏杆蓝细菌属物种以及一个宏基因组组装基因组。在此，我们描述了一种新培养的黏杆蓝细菌类成员——巴拿马角苔杆菌，它分离自一种热带角苔。角苔杆菌在14亿年前就与黏杆蓝细菌分化，并且其16S rDNA与环境样本的一致性较低。我们通过超微结构、生理及基因组分析发现，该物种具有独特的性状组合，这些性状仅与黏杆蓝细菌类或藻杆菌类共有。例如，与黏杆蓝细菌类似，它缺乏类囊体和生物钟基因，但类胡萝卜素生物合成途径却是藻杆菌的典型特征。此外，角苔杆菌拥有蓝细菌中光合系统和藻胆体相关基因集缩减程度最高的基因集之一。尽管如此，角苔杆菌仍能够在很宽的光照强度范围内进行产氧光合作用，尽管效率要低得多。鉴于其关键的系统发育位置、独特的性状组合以及可培养的特性，角苔杆菌为进一步阐明产氧光合作用的起源开启了一扇新窗口。
Cyanobacteria have played pivotal roles in Earth's geological history, especially during the rise of atmospheric oxygen. However, our ability to infer the early transitions in Cyanobacteria evolution has been limited by their extremely lopsided tree of life-the vast majority of extant diversity belongs to Phycobacteria (or "crown Cyanobacteria"), while its sister lineage, Gloeobacteria, is depauperate and contains only two closely related species of Gloeobacter and a metagenome-assembled genome. Here, we describe a new cultured member of Gloeobacteria, Anthocerotibacter panamensis, isolated from a tropical hornwort. Anthocerotibacter diverged from Gloeobacter over 1.4 Ga ago and has low 16S rDNA identities with environmental samples. Our ultrastructural, physiological, and genomic analyses revealed that this species possesses a unique combination of traits that are exclusively shared with either Gloeobacteria or Phycobacteria. For example, similar to Gloeobacter, it lacks thylakoids and circadian clock genes, but the carotenoid biosynthesis pathway is typical of Phycobacteria. Furthermore, Anthocerotibacter has one of the most reduced gene sets for photosystems and phycobilisomes among Cyanobacteria. Despite this, Anthocerotibacter is capable of oxygenic photosynthesis under a wide range of light intensities, albeit with much less efficiency. Given its key phylogenetic position, distinct trait combination, and availability as a culture, Anthocerotibacter opens a new window to further illuminate the dawn of oxygenic photosynthesis.