title: Respiratory interactions of soil bacteria with (semi)conductive iron-oxide minerals.
abstract: Pure-culture studies have shown that dissimilatory metal-reducing bacteria are able to utilize iron-oxide nanoparticles as electron conduits for reducing distant terminal acceptors; however, the ecological relevance of such energy metabolism is poorly understood. Here, soil microbial communities were grown in electrochemical cells with acetate as the electron donor and electrodes (poised at 0.2 V versus Ag/AgCl) as the electron acceptors in the presence and absence of iron-oxide nanoparticles, and respiratory current generation and community structures were analysed. Irrespective of the iron-oxide species (hematite, magnetite or ferrihydrite), the supplementation with iron-oxide minerals resulted in large increases (over 30-fold) in current, while only a moderate increase (∼10-fold) was observed in the presence of soluble ferric/ferrous irons. During the current generation, insulative ferrihydrite was transformed into semiconductive goethite. Clone-library analyses of 16S rRNA gene fragments PCR-amplified from the soil microbial communities revealed that iron-oxide supplementation facilitated the occurrence of Geobacter species affiliated with subsurface clades 1 and 2. We suggest that subsurface-clade Geobacter species preferentially thrive in soil by utilizing (semi)conductive iron oxides for their respiration.
authors.affiliation: Hashimoto Light Energy Conversion Project, ERATO, JST, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Souichiro
authors.initials: S
authors.lastname: Kato
authors.forename: Ryuhei
authors.initials: R
authors.lastname: Nakamura
authors.forename: Fumiyoshi
authors.initials: F
authors.lastname: Kai
authors.forename: Kazuya
authors.initials: K
authors.lastname: Watanabe
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Hashimoto
mesh_terms: D005290:Ferric Compounds / Q000378:metabolism*; D052203:Ferrosoferric Oxide / Q000378:metabolism; D020459:Genes, rRNA; D045302:Geobacter / Q000235:genetics / Q000378:metabolism*; D058085:Iron Compounds / Q000378:metabolism; D008903:Minerals / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology
chemical_list: D005290:Ferric Compounds; D058085:Iron Compounds; D008903:Minerals; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012987:Soil; C094886:goethite; C000499:ferric oxide; C092844:ferric oxyhydroxide; D052203:Ferrosoferric Oxide