Ecophysiological characterization of novel Chloroflexi to probe the evolution of photosynthesis

在2022财年，我们将野外数据、生物信息学和实验室实验相结合，对一种高度新颖的光养细菌“Candidatus Chlorohelix allophototropha”菌株L227-S17的生态学和生理学有了新的认识。在野外，我们重新访问了Oze国家公园（福岛县），并在富含铁的沉积物样本中发现了第二个类似l227 -17的种群。这些结果表明，L227-S17亲缘菌在当地的野外站点中是重复出现的，并且具有多样性，这为我们将来培养这些生物提供了基础。虽然我们没有在富铁湖泊（山满县Mizugaki湖）测序的宏基因组中检测到L227-S17亲属，但我们恢复了具有铁循环潜力的新基因组桶，为富铁生态系统的营养循环提供了新的思路。我们将继续分析2021财年的晴取湖数据集。利用生物信息学的方法，我们检索了160,000个公开的DNA/RNA测序数据集，探讨了L227-S17亲缘关系的全球多样性。从这次调查中恢复的基因组箱极大地扩展了已知的L227-S17进化枝的多样性，并为探索光合作用的进化提供了有价值的数据集。在实验室中，我们获得了令人信服的初步数据，即L227-S17培养物进行光驱动铁（II）氧化，这是一种被认为是早期地球营养循环关键的代谢，研究很少。总之，我们对“Ca. Chx”的生态生理研究。同种光噬菌（allophototropha）菌株L227-S17为探索地球上古代铁循环和光合作用历史提供了重要的基线数据。

In FY2022, we combined field data, bioinformatics, and laboratory experiments to gain new insights into the ecology and physiology of "Candidatus Chlorohelix allophototropha" strain L227-S17, a highly novel phototrophic bacterium. In the field, we revisited Oze National Park (Fukushima-ken) and detected a second L227-17-like population in iron-rich sediment samples. These results demonstrate that L227-S17 relatives are reoccurring and diverse in a local field site and let us plan to cultivate these organisms in future. Although we did not detect L227-S17 relatives in metagenomes we sequenced from an iron-rich lake (Lake Mizugaki, Yamanshi-ken), we recovered novel genomes bins with potential for iron cycling that shed new light on nutrient cycling in iron-rich ecosystems. We are continuing to analyze our Lake Harutori dataset from FY2021. Using bioinformatics, we probed the global diversity of L227-S17 relatives by searching >160,000 publicly available DNA/RNA sequencing datasets. Genome bins recovered from this survey greatly expand the known diversity of the L227-S17 clade and provide a valuable dataset to explore the evolution of photosynthesis. In the laboratory, we obtained compelling preliminary data that the L227-S17 culture performs light-driven iron(II) oxidation, a poorly studied metabolism thought to have been key to nutrient cycling on the early Earth. Altogether, our ecophysiological study of "Ca. Chx. allophototropha" strain L227-S17 provides an important baseline dataset for probing the ancient iron cycle and history of photosynthesis on Earth.