Microbial Interactions in the Arsenic Cycle: Adoptive Strategies and Applications in Environmental Management

Abstract

Arsenic (As) is a nonessential element that is often present in plants and in other organisms. However, it is one of the most hazardous of toxic elements globally. In many parts of the world, arsenic contamination in groundwater is a serious and continuing threat to human health. Microbes play an important role in regulating the environmental fate of arsenic. Different microbial processes influence the biogeochemical cycling of arsenic in ways that affect the accumulation of different arsenic species in various ecosystem compartments. For example, in soil, there are bacteria that methylate arsenite to trimethylarsine gas, thereby releasing arsenic to the atmosphere.In marine ecosystems, microbes exist that can convert inorganic arsenicals to organic arsenicals (e.g., di- and tri-methylated arsenic derivatives, arsenocholine,arsenobetaine, arsenosugars, arsenolipids). The organo arsenicals are further metabolized to complete the arsenic cycle.Microbes have developed various strategies that enable them to tolerate arsenic and to survive in arsenic-rich environments. Such strategies include As exclusion from cells by establishing permeability barrier, intra- and extracellular sequestration,active efflux pumps, enzymatic reduction, and reduction in the sensitivity of cellular targets. These strategies are used either singly or in combination. In bacteria,the genes for arsenic resistance/detoxification are encoded by the arsenic resistance operons (ars operon).In this review, we have addressed and emphasized the impact of different microbial processes (e.g., arsenite oxidation, cytoplasmic arsenate reduction, respiratory arsenate reduction, arsenite methylation) on the arsenic cycle. Microbes are the only life forms reported to exist in heavy arsenic-contaminated environments. Therefore,an understanding of the strategies adopted by microbes to cope with arsenic stress is important in managing such arsenic-contaminated sites. Further future insights into the different microbial genes/proteins that are involved in arsenic resistance may also be useful for developing arsenic resistant crop plants.

Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

“…Methods that have been developed to attenuate As such as electrocoagulation and electrodialysis [45,46], treatment with microorganisms to affect the biogeochemical cycling of As [7], and the adsorption of As onto a variety sorbents [47][48][49]. Among the sorbents used for As attenuation are organic polymers [50], and minerals such as dolomite [51], zeolites [52], and Al minerals such as alumina or gibbsite [53,54].…”

“…Therefore, if ligands that inhibit As adsorption can be removed or precipitated and ligands that enhance As adsorption can be added to As-containing site, it could be possible to develop improved As-remediation techniques. Arsenic adsorption may also be enhanced by the addition of magnetite to agricultural waste such as wheat straw [61], but adsorption of As can be reduced by microorganisms [7,66]. If it is possible to control the growth and metabolism of microorganisms present in As-containing water, then it could be possible to enhance As adsorption.…”

“…Arsenic is found in a variety of geochemical environments at aqueous concentrations varying from <0.5 to >5000 μg/L, and is found in a variety of geochemical environments [1,2]. Natural and anthropogenically-mediated biogeochemical interactions among arsenic species, biota, and minerals can affect the distribution, mobility, and toxicity of As in the environment [2][3][4][5][6][7][8]. Although recent work has posited that arsenic could be a potential biochemical and astrobiological proxy for phosphorus during biological evolution [9], this hypothesis is controversial [10].…”

The molecular diversity of arbuscular mycorrhizal fungi in the arsenic mining impacted sites in Hunan Province of China

“…As a result, As has been included in the list of 20 most hazardous substances by the Agency for Toxic Substances and Disease Registry (Dhuldhaj et al, 2013).…”

Fungal Bioweathering of Mimetite and a General Geomycological Model for Lead Apatite Mineral Biotransformations

“…The spread and ubiquity of As in the environment, its biological toxicity, and its enhanced redistribution due to anthropogenic activities are causes of major public concern (14-16, 18, 19). Anthropogenic arsenic sources include the use of agricultural pesticides, wood preservatives, and medicines, oil and coal burning for energy production, waste incineration and disposal, and industrial activities associated with metal acquisition and processing from mineral ores (18,19).More than 300 arsenic minerals occur in nature, and of these, ϳ60% occur as arsenates, 20% as sulfides and sulfosalts, 10% as oxides, and the rest as arsenites, arsenides, the native element, and metal alloys (14,16,(18)(19)(20). In primary arsenic-bearing minerals, arsenic is present as the anion arsenide (As 3Ϫ ) or diarsenide (As 2 6Ϫ ) or as sulfarsenide (AsS 3Ϫ ) in sulfidic ores in the form of arsenides of Fe, Cu, Co, and Ni (15,20).…”