[P006] Poster

1:00 PM - 1:50 PM JST(4:00 AM - 4:50 AM UTC)

[P03-366] Isolation of hydrogen-oxidizing bacteria using a continuous low-hydrogen supply system

○Yuta Michimori¹, Naoki Ohashi¹, Koudai Shiotsu¹, Yuna Ishida¹, Yuko Murayama¹, Yuusuke Yokooji¹, Haruyuki Atomi¹ (1. Kyoto Univ. (Japan))

Keywords:

hydrogen-oxidizing bacteria,cultivation,isolation

Since the industrial revolution, human economic activities have led to the consumption of fossil fuels, resulting in an increase in atmospheric carbon dioxide (CO₂) levels. In addition to short-term concerns regarding the impact of CO₂-induced greenhouse effects on the global environment, the use of non-renewable carbon resources poses a long-term sustainability issue. Therefore, there is a growing demand for technologies that regard atmospheric CO₂ as a “resource” and convert it into valuable carbon-based materials.Hydrogen-oxidizing bacteria are a group of microorganisms capable of producing organic compounds from CO₂ by obtaining energy and reducing power through the use of hydrogen as an electron donor and oxygen as a terminal electron acceptor. Hydrogen can be generated by water electrolysis using electricity derived from renewable energy sources, making it a promising system for supplying biomass, a useful carbon resource, from sustainable inputs. However, because hydrogen has low solubility in water, conventional cultivation methods for hydrogen-oxidizing bacteria have relied on sealed culture systems in which pressurized hydrogen is supplied to the headspace. While this method enables the cultivation of microorganisms that utilize high concentrations of hydrogen, it is not suitable for selectively enriching organisms that efficiently utilize low concentrations of hydrogen, as would be expected in natural environments.To address this issue, this study aimed to isolate hydrogen-utilizing microorganisms present in the environment by developing a cultivation system that continuously supplies small amounts of hydrogen gas under atmospheric pressure. Microbial cultivation from soil and aquatic samples was then conducted using this system.Samples were inoculated into multiple test tubes with stepwise decreasing hydrogen supply and cultured under various media and temperature conditions. As a result, stable microbial consortia capable of successive subculturing were obtained under several conditions.Genomic DNA extraction and long-read sequencing analyses were performed to identify the microbial species present in each consortium. This resulted in the recovery of multiple high-quality metagenome-assembled genomes (MAGs). Each MAG was analyzed for the presence of carbon fixation pathways, including the Calvin–Benson–Bassham cycle, as well as genes encoding hydrogenases. Based on these analyses, the microbial species responsible for CO₂ fixation within each consortium were investigated.