Acetogenic bacteria utilize light-driven electrons as an energy source for autotrophic growth

• Published in: Proceedings of the National Academy of Sciences - PNAS 2021-03, Vol.118 (9), p.1-7
• Main Authors: Jin, Sangrak, Jeon, Yale, Jeon, Min Soo, Shin, Jongoh, Song, Yoseb, Kang, Seulgi, Bae, Jiyun, Cho, Suhyung, Lee, Jung-Kul, Kim, Dong Rip, Cho, Byung-Kwan
• Format: Article
• Language: English
• Subjects: Biological Sciences
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2020552118

Acetogenic bacteria use cellular redox energy to convert CO₂ to acetate using the Wood–Ljungdahl (WL) pathway. Such redox energy can be derived from electrons generated from H₂ as well as from inorganic materials, such as photoresponsive semiconductors. We have developed a nanoparticle-microbe hybrid system in which chemically synthesized cadmium sulfide nanoparticles (CdS-NPs) are displayed on the cell surface of the industrial acetogen Clostridium autoethanogenum. The hybrid system converts CO₂ into acetate without the need for additional energy sources, such as H₂, and uses only light-induced electrons from CdS-NPs. To elucidate the underlying mechanism by which C. autoethanogenum uses electrons generated from external energy sources to reduce CO₂, we performed transcriptional analysis. Our results indicate that genes encoding the metal ion or flavin-binding proteins were highly up-regulated under CdS-driven autotrophic conditions along with the activation of genes associated with the WL pathway and energy conservation system. Furthermore, the addition of these cofactors increased the CO² fixation rate under light-exposure conditions. Our results demonstrate the potential to improve the efficiency of artificial photosynthesis systems based on acetogenic bacteria integrated with photoresponsive nanoparticles.