Figure 1.

(A) The coding gene of oxidoreducase AioE was spread in many genomes of As^III oxidation strains. (B) RT-PCR analysis illustrating the co-transcription of arsR1-arsC1-arsC2-acr3-1-aioE and their enhanced expression with the addition of As^III. RT-PCRs were performed with the primers in Table S1. A’, 129 bp, B’, 246 bp, C’, 274 bp, D’, 321 bp, E’, 139 bp, F’, 210 bp, G’, 226 bp, H’, 188 bp, and I’, 117 bp. Total RNA was extracted from strain GW4 grown in MMNH₄ medium with or without 0.25 mM As^III. M, the molecular weight marker (DL 2000 plus). All reverse transcriptase reactions contained 15 ng of RNA and each lane was loaded with 5 μL of the PCR product. Amplicon identities were confirmed by DNA sequencing. (C) Quantitative reverse transcriptase-PCR analysis of the genes involved in ars and aio gene island influenced by As^III. The 16 S rRNA gene was used as a reference. Data are shown as the mean of three replicates, with the error bars representing ± 1 SD. Amplicon identities were confirmed by DNA sequencing.