title: Light/electricity conversion by defined cocultures of Chlamydomonas and Geobacter.
abstract: Biological energy-conversion systems are attractive in terms of their self-organizing and self-sustaining properties and are expected to be applied towards environmentally friendly bioenergy processes. Recent studies have demonstrated that sustainable light/electricity-conversion systems, termed microbial solar cells (MSCs), can be constructed using naturally occurring microbial communities. To better understand the energy-conversion mechanisms in microbial communities, the present study attempted to construct model MSCs comprised of defined cocultures of a green alga, Chlamydomonas reinhardtii, and an iron-reducing bacterium, Geobacter sulfurreducens, and examined their metabolism and interactions in MSCs. When MSC bioreactors were inoculated with these microbes and irradiated on a 12-h light/dark cycle, periodic current was generated in the dark with energy-conversion efficiencies of 0.1%. Metabolite analyses revealed that G. sulfurreducens generated current by oxidizing formate that was produced by C. reinhardtii in the dark. These results demonstrate that the light/electricity conversion occurs via syntrophic interactions between phototrophs and electricity-generating bacteria. Based on the results and data in literatures, it is estimated that the excretion of organics by the phototroph was the bottleneck step in the syntrophic light/electricity conversion. We also discuss differences between natural-community and defined-coculture MSCs.
authors.affiliation: Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nishio
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Kazuya
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D001674:Bioelectric Energy Sources; D019149:Bioreactors / Q000382:microbiology; D016825:Chlamydomonas reinhardtii / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D018920:Coculture Techniques; D004560:Electricity; D005285:Fermentation; D005561:Formates / Q000378:metabolism; D045302:Geobacter / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D008027:Light
chemical_list: D005561:Formates