Effect of extracellular electron shuttles on arsenic-mobilizing activities in soil microbial communities

• Published in: Journal of hazardous materials 2018-01, Vol.342, p.571-578
• Main Authors: Yamamura, Shigeki, Sudo, Takayuki, Watanabe, Mirai, Tsuboi, Shun, Soda, Satoshi, Ike, Michihiko, Amachi, Seigo
• Format: Article
• Language: English
• Subjects: Anthraquinones - chemistry; Arsenate reduction; Arsenates; Arsenic - analysis; Arsenic - chemistry; Arsenic mobilization; Bacteria - chemistry; Bacteria - metabolism; Biodegradation, Environmental; Bioremediation; Electron shuttle; Electrons; Fe(III) reduction; Ferric Compounds - chemistry; Ferric Compounds - metabolism; Minerals - chemistry; Soil Microbiology
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2017.08.071

[Display omitted] •Electron shuttles were able to stimulate the As-mobilizing activities in natural soil microbial communities.•Firmicutes-related bacteria may play more important roles in As and Fe dissolution than previously suspected.•Electron shuttles occasionally enhanced accumulation of solid-phase Fe(II), which led to re-immobilization of As. Microbially mediated arsenate (As(V)) and Fe(III) reduction play important roles in arsenic (As) cycling in nature. Extracellular electron shuttles can impact microbial Fe(III) reduction, yet little is known about their effects on microbial As mobilization in soils. In this study, microcosm experiments consisting of an As-contaminated soil and microbial communities obtained from several pristine soils were conducted, and the effects of electron shuttles on As mobilization were determined. Anthraquinone-2,6-disulfonate (AQDS) and riboflavin (RF) were chosen as common exogenous and biogenic electron shuttles, respectively, and both compounds significantly enhanced reductive dissolution of As and Fe. Accumulation of Fe(II)-bearing minerals was also observed, which may lead to re-immobilization of As after prolonged incubation. Interestingly, Firmicutes-related bacteria became predominant in all microcosms, but their compositions at the lower taxonomic level were different in each microcosm. Putative respiratory As(V) reductase gene (arrA) analysis revealed that bacteria closely related to a Clostridia group, especially those including the genera Desulfitobacterium and Desulfosporosinus, might play significant roles in As mobilization. These results indicate that the natural soil microbial community can use electron shuttles for enhanced mobilization of As; the use of this type of system is potentially advantageous for bioremediation of As-contaminated soils.