Anaerobic Arsenite Oxidation by an Autotrophic Arsenite-Oxidizing Bacterium from an Arsenic-Contaminated Paddy Soil

Abstract

Microbe-mediated arsenic (As) redox reactions play an important role in the biogeochemical cycling of As. Reduction of arsenate [As(V)] generally leads to As mobilization in paddy soils and increased As availability to rice plants, whereas oxidation of arsenite [As(III)] results in As immobilization. A novel chemoautotrophic As(III)-oxidizing bacterium, designated strain SY, was isolated from an As-contaminated paddy soil. The isolate was able to derive energy from the oxidation of As(III) to As(V) under both aerobic and anaerobic conditions using O2 or NO3(-) as the respective electron acceptor. Inoculation of the washed SY cells into a flooded soil greatly enhanced As(III) oxidation to As(V) both in the solution and adsorbed phases of the soil. Strain SY is phylogenetically closely related to Paracoccus niistensis with a 16S rRNA gene similarity of 96.79%. The isolate contains both the denitrification and ribulose 1,5-bisphosphate carboxylase/oxygenase gene clusters, underscoring its ability to denitrify and to fix CO2 while coupled to As(III) oxidation. Deletion of the aioA gene encoding the As(III) oxidase subunit A abolished the As(III) oxidation ability of strain SY and led to increased sensitivity to As(III), suggesting that As(III) oxidation is a detoxification mechanism in this bacterium under aerobic and heterotrophic growth conditions. Analysis of the aioA gene clone library revealed that the majority of the As(III)-oxidizing bacteria in the soil were closely related to the genera Paracoccus of α-Proteobacteria. Our results provide direct evidence for As(III) oxidation by Paracoccus species and suggest that these species may play an important role in As(III) oxidation in paddy soils under both aerobic and denitrifying conditions.

Prospective role of indigenousExiguobacterium profundumPT2 in arsenic biotransformation and biosorption by planktonic cultures and biofilms

“…Microbial As 5+ reduction may be carried out by using As 5+ as an electron acceptor or as a part of As detoxification mechanism by As 5+ reductase (Zhang et al . ). However, heterotrophic bacteria overcome As stress through As 3+ oxidation, while chemoautotrophic bacteria use energy derived from As 3+ oxidation (Zhang et al .…”

“…However, heterotrophic bacteria overcome As stress through As 3+ oxidation, while chemoautotrophic bacteria use energy derived from As 3+ oxidation (Zhang et al . ; Bagade et al . ; Sanyal et al .…”

“…Conclusion: Indigenous As-resistant E. profundum PT2 was found capable of As transformation and biosorption both in the form of planktonic cultures and biofilms. Significance and Impact of the Study: Indigenous biofilm forming E. profundum PT2 revealing As biosorption and biotransformation potential is presented an eco-friendly and cost-effective source for As remediation that can be implemented for waste water treatment.DNA-DNA and DNA-protein linkages (Kaur et al 2009;Sousa et al 2015;Zhang et al 2015). Natural processes of volcanic eruptions, rocks weathering and leaching, and anthropogenic activities of mining, smelting and pesticides are continuously increasing the amount of As in the environment.…”

“…DNA-DNA and DNA-protein linkages (Kaur et al 2009;Sousa et al 2015;Zhang et al 2015). Natural processes of volcanic eruptions, rocks weathering and leaching, and anthropogenic activities of mining, smelting and pesticides are continuously increasing the amount of As in the environment.…”

Long-term performance of rapid oxidation of arsenite in simulated groundwater using a population of arsenite-oxidizing microorganisms in a bioreactor

“…Most of the known arsenite-oxidizing bacteria (AOBs) are heterotrophic, whereas other AOBs are chemoautotrophic, which are able to use CO 2 as the sole carbon source. It was also found that a few of bacteria were able to oxidize arsenite in anaerobic condition using nitrate (Rhine et al, 2006;Zhang et al, 2015a) or chlorate (Sun et al, 2010) as the terminal electron acceptor, and arsenite as the electron donor.…”