Transcriptional Activity of Arsenic-Reducing Bacteria and Genes Regulated by Lactate and Biochar during Arsenic Transformation in Flooded Paddy Soil

• Published in: Environmental science & technology Vol. 52; no. 1; pp. 61 - 70
• Main Authors: Qiao, Jiang-tao, Li, Xiao-min, Hu, Min, Li, Fang-bai, Young, Lily Y, Sun, Wei-min, Huang, Weilin, Cui, Jiang-hu
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.01.2018
• Subjects: Arsenic; Bacteria; Bioavailability; biochar; Charcoal; chemical analysis; Electron transfer; Enterobacteriaceae; environmental science; Flooded soils; Genes; Geobacter; Iron; Lactic acid; Microcosms; Microorganisms; paddy soils; Phylogeny; Plants (botany); Reduction; resistance genes; ribosomal RNA; rice; Rice fields; rRNA 16S; Sediments; Sequences; Soil analysis; Soil chemistry; Soil contamination; Substrates; Transcription; transcription (genetics)
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.7b03771

Organic substrates and biochar are important in controlling arsenic release from sediments and soils; however, little is known about their impact on arsenic-reducing bacteria and genes during arsenic transformation in flooded paddy soils. In this study, microcosm experiments were established to profile transcriptional activity of As­(V)-respiring gene (arrA) and arsenic resistance gene (arsC) as well as the associated bacteria regulated by lactate and/or biochar in anaerobic arsenic-contaminated paddy soils. Chemical analyses revealed that lactate as the organic substrate stimulated microbial reduction of As­(V) and Fe­(III), which was simultaneously promoted by lactate+biochar, due to biochar’s electron shuttle function that facilitates electron transfer from bacteria to As­(V)/Fe­(III). Sequencing and phylogenetic analyses demonstrated that both arrA closely associated with Geobacter (>60%, number of identical sequences/number of the total sequences) and arsC related to Enterobacteriaceae (>99%) were selected by lactate and lactate+biochar. Compared with the lactate microcosms, transcriptions of the bacterial 16S rRNA gene, Geobacter spp., and Geobacter arrA and arsC genes were increased in the lactate+biochar microcosms, where transcript abundances of Geobacter and Geobacter arrA closely tracked with dissolved As­(V) concentrations. Our findings indicated that lactate and biochar in flooded paddy soils can stimulate the active As­(V)-respiring bacteria Geobacter species for arsenic reduction and release, which probably increases arsenic bioavailability to rice plants.