| 研究実績の概要 |
In FY2021, we continued to characterize the ecophysiology of “Candidatus Chlorohelix allophototropha”, a highly novel phototrophic bacterium that we enriched from an iron-rich lake in Canada. We established a stable co-culture of “Ca. Chx. allophototropha” with a putative iron-reducing bacterium. By analyzing this co-culture using HPLC and absorption spectroscopy, we provided strong evidence that “Ca. Chx. allophototropha” uses bacteriochlorophyll c and chlorosomes to perform phototrophy. We also sequenced the complete genome of “Ca. Chx. allophototropha”. Alongside physiological approaches, we sequenced metagenomes of samples collected from the iron-rich marshes of Oze National Park (Fukushima Prefecture), and we recovered the partial genome of a novel species related to “Ca. Chx. allophototropha”. This novel species is the first known representative of the “Ca. Chlorohelix” clade in Japan, and its discovery sheds light on the global ecology of the clade. We also analyzed metagenomes and metatranscriptomes of samples we collected from Lake Harutori in FY2020 and, although “Ca. Chx. allophototropha” relatives were not detected, we recovered multiple novel microbial genomes that we will analyze further in FY2022. Overall, this research is providing an important foundation to use “Ca. Chx. allophototropha” as a model organism to understand the evolution and biochemistry of photosynthesis.
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| 今後の研究の推進方策 |
Challenges in cultivating “Ca. Chx. allophototropha” in FY2020 caused us to expand the ecological and genomic focus of the project while adjusting our goals for physiological characterization. Now that we have a stable and growing co-culture of “Ca. Chx. allophototropha”, we will explore novel methods to grow high biomass cultures of “Ca. Chx. allophototropha” for physiological analysis. We will also test the potential of the strain to perform iron(II)-oxidizing phototrophy, a poorly understood metabolism that is of high research interest because of its potential role in early Earth ecosystems. We have downloaded more than 100,000 publicly available 16S ribosomal gene amplicon sequencing datasets from the MGnify database, and we will finish scanning these datasets in FY2022 to gain insights into the global diversity and ecology of the novel “Ca. Chloroheliales” clade. Lastly, we will complete and summarize our metagenome analyses from Oze National Park and Lake Harutori
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