[U-11] CO環境の生命惑星化学

[U11-P14] COとCO₂を基質とした微生物酢酸生成の分子内炭素同位体分別

*佐藤 悠太¹、鈴木 志野²、加藤 創一郎³、笠井 拓哉³、山田 桂大¹、上野 雄一郎^1,5,4、Alexis Gilbert¹ (1.東京工業大学、2.宇宙航空研究開発機構、3.産業技術総合研究所、4.海洋研究開発機構、5.東京工業大学地球生命研究所)

キーワード：酢酸生成菌、CO固定、分子内同位体分析

Position-Specific Isotope Analysis (PSIA) has been utilized in a wide range of fields to tracing the sources and sink processes of molecules in environment. In this research, we focus on intramolecular carbon isotope distribution of acetic acid, which is often produced by microbial acetogenesis and plays an important role in the biogeochemical carbon cycle. The carbon isotopic relationship between methyl and carboxyl positions of acetate, which are through different pathways in acetogenic metabolisms, could be important to interpret the mechanisms of acetate production. We have incubated acetogenic bacteria and methanogenic archaea, both of which are capable of converting both CO₂ and CO into acetic acid. The results showed that the acetate exhibited significant differences between carboxyl and methyl positions in acetic acid (Δ_car-met >30‰) when the carbon source was CO, whereas Δ_car-met value was much smaller (< 9‰) when the acetic acid was produced from CO₂. Based on the experimental results, we provide a new interpretation of the carbon flows in the metabolism (i.e., Wood-Ljungdal pathway). The observed large Δ_car-met can be explained by a shortage of energy and CO₂ pool under CO condition. The results also demonstrated the possibility that the PSIA of acetic acid could be utilized for distinguishing carbon sources for microbial acetogenesis in the environment.