Acclimation of arsenic-resistant Fe(II)-oxidizing bacteria in aqueous environment

This study investigated the potential of the Fe(II)-oxidizing bacteria in removing arsenic in aqueous environment. The bacteria were isolated from the batch of tap water and rusty iron wires, and were acclimated to culture media amended with arsenic concentrations, gradually increasing from 100 μg L−1 to 100 mg L−1. Acclimated bacteria with enhanced arsenic tolerance were used to remove arsenic from the aqueous solution. These bacteria belonged to Pseudomonas species according to 16S rRNA gene sequences. Extracellular enzymes produced by these bacteria played important roles in microbial Fe(II) oxidization and Fe oxide precipitation. Moreover, these bacteria survived and propagated in high arsenic condition (100 mg L−1 As). However, after As(III/V) acclimation, morphological characteristics of the bacteria showed some changes, e.g., shrinking of long bacillus. XRD (X-ray diffraction) patterns indicated that Fe oxide precipitations by Fe(II)-oxidizing bacteria in Fe-rich culture medium were poorly-crystallized ferrihydrites. Adsorption on the biogenic ferrihydrites greatly contributed to high arsenic removal efficiency of Fe(II)-oxidizing bacteria.