Isolation and characterization of aerobic, culturable, arsenic-tolerant bacteria from lead–zinc mine tailing in southern China

Bioremediation of arsenic (As) pollution is an important environmental issue. The present investigation was carried out to isolate As-resistant novel bacteria and characterize their As transformation and tolerance ability. A total of 170 As-resistant bacteria were isolated from As-contaminated soils at the Kangjiawan lead–zinc tailing mine, located in Hunan Province, southern China. Thirteen As-resistant isolates were screened by exposure to 260 mM Na 2 HAsO 4 ·7H 2 O, most of which showed a very high level of resistance to As 5+ (MIC ≥ 600 mM) and As 3+ (MIC ≥ 10 mM). Sequence analysis of 16S rRNA genes indicated that the 13 isolates tested belong to the phyla Firmicutes, Proteobacteria and Actinobacteria , and these isolates were assigned to eight genera, Bacillus, Williamsia, Citricoccus, Rhodococcus, Arthrobacter, Ochrobactrum, Pseudomonas and Sphingomonas . Genes involved in As resistance were present in 11 of the isolates. All 13 strains transformed As (1 mM); the oxidation and reduction rates were 5–30% and 10–51.2% within 72 h, respectively. The rates of oxidation by Bacillus sp. Tw1 and Pseudomonas spp. Tw224 peaked at 42.48 and 34.94% at 120 h, respectively. For Pseudomonas spp. Tw224 and Bacillus sp. Tw133, the highest reduction rates were 52.01% at 48 h and 48.66% at 144 h, respectively. Our findings will facilitate further research into As metabolism and bioremediation of As pollution by genome sequencing and genes modification.