Isolation of Arthrobacter FX8 capable of removing arsenic by biomineralization

Abstract:

[Background] The contamination of arsenic (As), a highly toxic metalloid, in water is aggravating, which threatens human health. The common method used for removing As is adsorption, and it is urgent to develop efficient As removal methods. [Objective] To characterize an iron-oxidizing bacterial strain FX8 isolated from the surface soil of iron ore, so as to use the iron mineral (adsorbent) produced by the strain via oxidizing Fe(II) for removing As. [Methods] The strain was identified based on morphological, physiological, and biochemical characteristics and genome-wide sequencing evidence. The concentrations of total Fe and Fe(II) were determined by phenanthroline spectrophotometry. The iron oxide precipitates were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive spectrometer. The concentration of total As was determined by high performance liquid chromatography in combination with hydride generation and atomic fluorescence spectroscopy. [Results] Strain FX8 was Gram-positive and aerobic, with while and round colonies. Its cells were rod-shaped with the size of (0.5-2.5) μm×(0.13-0.25)μm. FX8 was identified as a strain of Arthrobacter. It could oxidize Fe(II) to generate iron oxide precipitates which were an amorphous Fe(III) mineral with poor crystallinity and a large amount of biological impurities. Strain FX8 oxidized Fe(II) by producing extracellular enzymes. The strain cultured with As(III) or As(V) at 28℃ and 150 r/min showed the total Fe removal rates of 100% in 48 h and the corresponding total As removal rates of 99.54% and 99.86%, respectively. When the extracellular enzyme liquid of strain FX8 was added into the As(III) or As(V) system, the total Fe removal rates reached 100% in 2 h, and the corresponding total As removal rates were 99.45% and 100%, respectively. [Conclusion] Strain FX8 is an iron-oxidizing bacterium, and the iron biomineralization with its extracellular enzyme liquid outperforms strain-arsenic coculture in the removal of As. The findings provide new biomaterials and theoretical references for the efficient remediation of As-contaminated water.