The candidate phyla radiation (CPR) is a diverse group of uncultured bacterial lineages with poorly understood metabolic functions. CPR bacteria can represent a large proportion of the total planktonic microbial community in subarctic thermokarst lakes, but their functional roles remain unexplored. We applied sequential water filtration and metagenomic shotgun sequencing to a peatland permafrost thaw lake, and found high proportions of CPR bacteria in both summer and winter (> 40% of 16S rRNA reads in the 0.02–0.22 μm pore‐size fraction). The metagenome‐assembled genomes of CPR bacteria representatives showed capacities to degrade and ferment permafrost‐ and peatland‐derived organic matter. Potential products of their metabolic activities included acetate, CO₂, and hydrogen, implying a syntrophic relationship with other community members, including methanogens and methanotrophs. The results indicate biogeochemical interdependencies in organic matter utilization within thermokarst microbial communities, with CPR members playing a key intermediate role in carbon and methane cycling.

中文翻译：

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超小且丰富：候选的门类辐射细菌是热喀斯特湖生态系统中碳转化的潜在催化剂

候选门静脉辐射（CPR）是一组未培养的细菌谱系，其代谢功能了解甚少。CPR细菌可在北极热喀斯特湖中占浮游微生物总数的很大一部分，但其功能作用仍待探索。我们应用序贯水过滤和宏基因组鸟枪法测序的多年冻土泥炭地解冻湖泊，发现细菌CPR高比例的在夏季和冬季（>的16S rRNA的40％在0.02-0.22读取 μ米孔径部分）。由CPR细菌组成的由基因组组装的基因组显示出降解和发酵永冻土和泥炭地有机物的能力。它们的代谢活动的潜在产物包括乙酸盐，CO ₂和氢，暗示与其他社区成员（包括产甲烷菌和甲烷营养菌）之间存在营养关系。结果表明，热岩溶微生物群落中有机物利用的生物地球化学相互依赖性，CPR成员在碳和甲烷循环中起着关键的中间作用。