[U-11] Biogeochemistry of CO world

[U11-P14] Intramolecular ¹³C distribution of microbial acetate from CO and CO₂

*Sato Yuta¹, Shino Suzuki², Soichiro Kato³, Takuya Kasai³, Keita Yamada¹, Yuichiro Ueno^1,5,4, Alexis Gilbert¹ (1.Tokyo Institute of Technology, 2.Japan Aerospace Exploration Agency, 3.National Institute of Advanced Industrial Science and Technology, 4.Japan Agency for Marine-Earth Science and Technology, 5.Earth-Life Science Institute)

Keywords:Acetogenesis, CO fixiation, Position-Specific Isotope Analysis (PSIA)

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.