Arsenate dissimilatory reduction

Zobrist.J., Dowdle, R.S., Davis, J.A. Orem-land, R.S. (2000) Mobilization of arsenite by dissimilatory reduction of adsorbed arsenate. Envon. Sci. Technol. 34 4747-4753... 

Oremland, R.S., Dowdle, P.R., Hoeft, S. et al. (2000) Bacterial dissimilatory reduction of arsenate and sulfate in meromictic Mono Lake, California. Geochimica et Cosmochimica Acta, 64(18), 3073-84. 

Oremland, R., and Stolz, J. (2000). Dissimilatory reduction of selenate and arsenate in nature. In Environmental Microbe-Metal Interactions,ed. Lovley, D. R., ASM Press, Washington, DC, 199-224. 

Dowdle, P. R., Laverman, A. M., and Oremland, R. S. (1996). Bacterial dissimilatory reduction of arsenic(V) and arsenic(in) in anoxic sediments. Appl. Environ. Microbiol. 62, 1664-1669. 

Microbial reduction of arsenate to arsenite may oceur by at least two principal mechanisms dissimilatory reduction where As(V) is utilized as a terminal electron acceptor during anaerobic respiration (52-57), and detoxifieation activity which involves an arsenate reductase and an arsenite efflux pump (58-65). Given... 

Table 2 Approximate Time Scales of Microbiologically Mediated Reduction of Arsenate to Arsenite Performed by Bacteria Capable of Utilizing As(V) as a Terminal Electron Acceptor During Anaerobic Respiration (Dissimilatory Reduction) or by Organisms Either Containing, or Presumed to Contain, ars Genes that Code for an Arsenate Reductase and an Arsenite Efflux Pump...

Newman et al. (56), and Rochette et al. (68) suggest that the reduction of arsenate by dissolved sulfide is very slow at circumneutral pH values. However, at pH values less than 5, the reduction rates of arsenate due to sulfide may be significant in natural systems, where half-lives as short as 21 hr have been reported (68) for this abiotic pathway (Table 3). Rochette et al. (68) also revealed the potential importance of intermediate As-O-S species in electron transfer reactions between sulfide and arsenate, such as H2 As OsS H2As 02S , and H2 As OS2. It is not known whether these chemical species may also serve as important redox active species for microbial metabolism. These authors have also compared the rates of As(V) reduction in the presence of sulfide versus those rates expected via dissimilatory reduction by an arsenate-respiring organism (strain SES-3) (54) and for those measured in lake sediments (69) at pH values less than 5, reduction rates due to dissolved sulfide can become more significant than reduction rates due to anaerobic respiration where As(V) is used as the terminal electron acceptor (Fig. 8). 

Newman DK, EK Kennedy, JD Coates, D Ahmann, DJ Ellis, DR Lovley, EMM Morel (1997) Dissimilatory arsenate and sulfate reduction in Desulfotomaculum auripigmentum sp. nov. Arch Microbiol 168 ... 

K. (2002) Potential remobdization of toxic anions during reduction of arsenated and chro-mated schwertmannite by the dissimilatory Fe(III)-reducing bacterium AcidiphUium cryp-tum JF-5 Water.Air, Soil pollution Focus 2 ... 

FIGURE 72.2. Arsenic detoxification mechanisms (reduction, oxidation, methylation, and resistance) in prokaryotes. (A) Respiratory arsenate reductase (Arr) is involved in the reduction of As(V) by the dissimilatory arsenate respiring organisms. (B) Arsenite oxidase (Aox/Aso) is responsible for oxidation of As(III) by chemoautotrophic or heterotrophic arsenite oxidizers. 

Newman D. K., Kennedy E., Coates J. D., Ahmann D., Ellis D. J., et al. (1997b) Dissimilatory arsenate and sulfate reduction in Desulfotomaculum auripidmentum sp. nov. Arch. Microbiol. 168, 380—388. 

Desorption on Iron and Arsenic Reduction The effects of biological (dissimilatory) Fe(III) and As(V) reduction on As transport under dynamic flow conditions in an Fe (hydr)oxide-dominated system illustrate the complexity of reactions influencing arsenic dynamics within soils. We examined the impact of a model freshwater anaerobic bacterium, Sulfurosprillum harnesii strain SES-3, that reduces both Fe(III) and As(V) through respiratory processes (Oremland et al., 1994 Zobrist et al., 2000), on the desorption of arsenic from ferrihydrite-coated sands (Herbel and Fendorf, 2005, 2006). As noted above for As(III)-loaded... 

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