2026-10-14 北海道大学
Alteromonas属による無機炭素の取り込みと、深海における炭酸固定への寄与
＜関連情報＞
- https://www.hokudai.ac.jp/news/2026/10/alteromonas2.html
- https://www.nature.com/articles/s41561-026-02013-1
深海における無機炭素固定への補充反応（アナプレロシス）の大きな寄与 Major contribution of anaplerosis to inorganic carbon fixation in the dark ocean
C. Amano, U. Willhelm, T. Koch, T. Reinthaler, R. L. Hansman, E. Sintes, G. J. Herndl, J. M. González & F. Baltar
Nature Communications Published:15 June 2026
DOI:https://doi.org/10.1038/s41561-026-02013-1
Abstract
While CO2 fixation by photo- and chemolithoautotrophs is a central process of the global carbon cycle, many organisms also incorporate inorganic carbon into organic compounds through anaplerotic carbon fixation, a process that replenishes intermediates of central metabolic pathways. However, the active drivers and quantitative importance of anaplerotic carbon fixation in the oceanic carbon cycling remain poorly understood. Here, through analysis of global ocean multi-omics datasets, we identified widespread expression of enzymes involved in this process, especially phosphoenolpyruvate carboxylase. The heterotrophic bacterial genus Alteromonas, a globally distributed marine taxon lacking genes for autotrophic carbon fixation pathways, exhibited particularly high transcriptional and proteomic activity for this enzyme. Laboratory incubations confirmed that Alteromonas assimilated dissolved inorganic carbon (DIC) into biomass, with rates regulated by temperature and organic matter availability. Single-cell tracer analyses of the deep ocean microbial communities quantified Alteromonas’s contribution at about 17% of total dark DIC fixation (median; confidence interval, 10–28%), equivalent to a potential global flux of about 0.2 PgC yr−1. These results reveal substantial DIC fixation via anaplerosis, indicating that dark carbon fixation is partly supported by heterotrophic metabolism and modulated by environmental conditions, with responses that may differ from those of canonical autotrophic processes.
