Bacterial arsenate reduction

Fig. 33.2. Factors controlling reaction rate (expressed per kg water, as r/nw) in the simulation of bacterial arsenic reduction, including kinetic factors FD and Fa, thermodynamic potential factor FT, and biomass concentration [X], Biomass concentration determines the rate early in the simulation, but later the thermodynamic drive exerts the dominant control.

Given recent advances in modes of bacterial arsenate reduction (Saltikov and Newman, 2003), the primary means by which arsenic is reduced in nonsulfidic systems, and probably in all systems that have pH values in the circumneutral range or higher (Rochette et al., 2000), we can further extend our view of arsenic... 

Kirk, M.F., T.R. Holm, J. Park, Q. Jin, R. A. Sanford, B.W. Fouke and C. M. Bethke, 2004, Bacterial sulfate reduction limits natural arsenic contamination of groundwater. Geology 32,953-956. 

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. 

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. 

E KA Rittle, JI Drever, PJS Colberg. Precipitation of arsenic during bacterial sulfate reduction. Geomicrobiol J 13 1-11, 1995. 

Figure 9 Yeast5. cerevisiae cell with small daughter cell bud and proteins of arsenate reduction and transport. Acr2p the yeast cytoplasmic arsenate reductase. Acr3p the potential-driven membrane arsenite efflux protein, equivalent to bacterial ArsB. Ycflp the novel As(III)-3 GSH adduct carrier than transports the adduct complex into the cell vacuole compartment, functioning as an ATPase.

Table 1 Novel Bacterial and Archaeal Isolates That Can Grow by Respiratory Arsenate Reduction...

PR Dowdle, AM Lavennan, RS Oremland. Bacterial dissknilatory reduction of arsenic (V) to arsenic (Hi) in anoxic sediments. Appl Environ Microbiol 62 1664-1669, 1996. 

The foregoing shows that arsenite in aerobic environments can undergo bacterial oxidation to arsenate. Since, as shown in the chapter on arsenate reduction, some anaerobic bacteria have the ability to reduce As(V) to different lower oxidation states, bacterial arsenite oxidation must represent part of a microbial arsenic cycle. Microbial activity can also mobilize arsenic in some minerals as arsenite and/ or arsenate. These microbial activities have to be considered in any assessment of environmental arsenic pollution. 

Figure 9. ArsC and y-ECS catalyzed reactions. The bacterial arsenate reductase (ArsC) catalyzes the electrochemical reduction of arsenate to arsenite. The bacterial y-glutamylcysteine synthetase (y-ECS) catalyzes the formation of y-glutamylcysteine (y-EC) from the amino acids glutamate and cysteine and is the committed step in the synthesis of glutathione (GSH) and phytochelatins, PCs (indicated by three arrows). Reduced arsenite can bind organic thiols (RS) such as those in y-EC, GSH, and PCs through the replacement of oxygen by organic sulfttr species.

Silver S, LT Phung (2005) Genes and enzymes in bacterial oxidation and reduction of inorganic arsenic. Appl Environ Microbiol 71 599-608. 

Johnson, D.L. 1972. Bacterial reduction of arsenate in seawater. Nature (Lond.) 240 44-45. 

At present, most contaminated aquifers in Quaternary delta plains are thought to contain arsenic mobilized under anoxic conditions by bacterial activity, which is driven by high concentrations of NOM (Smedley and Kinniburgh, 2002 Smedley, 2005). Arsenic sorbed on metal (oxy)(hydr)oxides is liberated by reductive dissolution (Chapter 3). The best-known example is the Bengal basin, where arsenic is widely present in Holocene (less than 11 500 years old) sediments, while the underlying, oxidized aquifers with Pleistocene (11500-1.75 million years old) sediments are thought to have very low concentrations of arsenic. Similar conditions may occur in Cambodia, Vietnam, Myanmar, and elsewhere... 

Johnson, D. L. (1972). Bacterial reduction of arsenate in sea water. Nature (London) 240, 44-45. 

Arsenate reductase can reduce arsenate to arsenite, and is involved in bacterial resistance to arsenic however, the reduction can also be mediated nonezymatically by reduced glutathione. The arsenate reductase utilizes thioredoxin and glutaredoxin rather than glutathione which is usually postulated to play a role in biomethylation. The cytosolic and periplasmic, two different arsenate reductases, exist in microorganisms encoded by ars and arr systems. Escherichia... 

Macur, R.E., Jackson, C.R., Botero, L.M., McDermott, T.R., Inskeep, W.P. (2004). Bacterial populations associated with the oxidation and reduction of arsenic in an unsaturated soil. Environ. Sci. Technol. 38 104-11. 

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