Microbial arsenate respiration

Microbial arsenate respiration contributes to the mobilization of arsenic from the solid to the soluble phase in various locales worldwide. In particular, microbial respiratory reduction of arsenate, As(V), to arsenite, As(III), is thought... 

DK Newman, D Ahmann, FMM Morel. A brief review of microbial arsenate respiration. Geomicrobiol J 15 255-268, 1998. 

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). 

Fig. 33.1. Results of a batch experiment (symbols) by Blum et al. (1998) in which Bacillus arsenicoselenatis grows on lactate, using arsenate [As(V)] as an electron acceptor. Solid lines show results of integrating a kinetic rate model describing microbial respiration and growth.

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... 

Stewart PS (1996) Theoretical aspects of antibiotic diffusion into microbial biofilms. Antmicroh Agents Chemother 40 2517—2522 Stewart PS, Hamilton I4A, Goldstein BR, Schneider BT (1996) Modeling biocide action against biofihns. Biotechnol Bioeng 49 445—455 Stolz JF, Oremland RS (1999) Bacterial respiration of arsenic and selenium. FEMS Microbiol Rev 23 615-627... 

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