title: Arsenic dissolution from Japanese paddy soil by a dissimilatory arsenate-reducing bacterium Geobacter sp. OR-1.
abstract: Dissimilatory As(V) (arsenate)-reducing bacteria may play an important role in arsenic release from anoxic sediments in the form of As(III) (arsenite). Although respiratory arsenate reductase genes (arrA) closely related to Geobacter species have been frequently detected in arsenic-rich sediments, it is still unclear whether they directly participate in arsenic release, mainly due to lack of pure cultures capable of arsenate reduction. In this study, we isolated a novel dissimilatory arsenate-reducing bacterium, strain OR-1, from Japanese paddy soil, and found that it was phylogenetically closely related to Geobacter pelophilus. OR-1 also utilized soluble Fe(III), ferrihydrite, nitrate, and fumarate as electron acceptors. OR-1 catalyzed dissolution of arsenic from arsenate-adsorbed ferrihydrite, while Geobacter metallireducens GS-15 did not. Furthermore, inoculation of washed cells of OR-1 into sterilized paddy soil successfully restored arsenic release. Arsenic K-edge X-ray absorption near-edge structure analysis revealed that strain OR-1 reduced arsenate directly on the soil solid phase. Analysis of putative ArrA sequences from paddy soils suggested that Geobacter-related bacteria, including those closely related to OR-1, play an important role in arsenic release from paddy soils. Our results provide direct evidence for arsenic dissolution by Geobacter species and support the hypothesis that Geobacter species play a significant role in reduction and mobilization of arsenic in flooded soils and anoxic sediments.
authors.affiliation: Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo-city, Chiba 271-8510, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ohtsuka
authors.forename: Noriko
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Makino
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sakurai
authors.forename: Kenta
authors.initials: K
authors.lastname: Kimura
authors.forename: Keitaro
authors.initials: K
authors.lastname: Kudo
authors.forename: Eri
authors.initials: E
authors.lastname: Homma
authors.forename: Dian Tao
authors.initials: DT
authors.lastname: Dong
authors.forename: Seigo
authors.initials: S
authors.lastname: Amachi
mesh_terms: D001151:Arsenic / Q000737:chemistry / Q000378:metabolism*; D005290:Ferric Compounds / Q000737:chemistry; D045302:Geobacter / Q000378:metabolism*; D012988:Soil Microbiology
chemical_list: D005290:Ferric Compounds; C092844:ferric oxyhydroxide; D001151:Arsenic