Ecophysiological characterization of novel Chloroflexi to probe the evolution of photosynthesis

在2022财年，我们将现场数据、生物信息学和实验室实验相结合，对高度新颖的光营养细菌“假丝酵母绿螺旋体异光营养”菌株L227-S17的生态和生理有了新的认识。在野外，我们再次访问了小泽国家公园(福岛-肯)，并在富含铁的沉积物样本中检测到第二个L227-17类种群。这些结果表明L227-S17的亲缘关系在当地的野外地点是重复出现的和多样化的，并让我们计划在未来培养这些生物。虽然我们没有在我们从一个富含铁的湖泊(Yamanshi-Ken，Mizugaki湖)测序的超基因组中发现L227-S17的近亲，但我们发现了具有潜在铁循环潜力的新的基因组箱，这为富铁生态系统中的营养循环提供了新的线索。我们正在继续分析2021财年Harutori湖的数据集。利用生物信息学，我们通过搜索16万个公开可用的DNA/RNA测序数据集，探索了L227-S17近缘基因的全球多样性。从这次调查中发现的基因组库极大地扩展了L227-S17分支的已知多样性，并为探索光合作用的进化提供了有价值的数据集。在实验室里，我们获得了令人信服的初步数据，L227-S17培养执行光驱动的铁(II)氧化，这是一种研究较少的新陈代谢，被认为是地球早期营养循环的关键。总之，我们对异光营养钙细菌L227-S17菌株的生态生理研究为探索地球上古老的铁循环和光合作用历史提供了重要的基线数据集。

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.