Biomedical subjects

Shigeki Yamamura

Publications and source records attributed to Shigeki Yamamura.

3 recordsLinked to original sources

PubMed2006

Reduction kinetics of As (V) to As (III) by a dissimilatory arsenate-reducing bacterium, Bacillus sp. SF-1.

This study proposes a kinetic model that accounts for the toxicity of both arsenate and arsenite and characterizes the arsenate reduction ability of a dissimilatory arsenate-reducing bacterium, Bacillus sp. SF-1 as a bioremediation agent. The model results correlated well with a series of batch reduction experiments conducted anaerobically in serum bottles with initial arsenate concentrations of 360, 735, and 1,500 mg-As/L. The reduction rate was expressed by the Haldane equation that describes the inhibitory effect of high concentrations of arsenate. The reduction rate constant k(r), half saturation constant K(S), and inhibition constant K(I) were estimated respectively as 1.2 x 10(9) mg-As/cells/h, 1.5 x 10(2) mg-As/L, and 4.2 x 10(2) mg-As/L. Lethal effects of arsenite that is accumulated as the end-product of arsenate reduction were expressed by the first-order term with a lethal constant of 2.7 x 10(-4) L/mg-As/h. The yield for the bacterial cells by arsenate respiration was estimated at 4.0 x 10(8) cells/mg-As.

Arsenates↗

PubMed2005

Arsenic extraction from solid phase using a dissimilatory arsenate-reducing bacterium.

We investigated the feasibility of a novel bioremedial strategy for arsenic-contaminated soil using a dissimilatory arsenate-reducing bacterium (DARB), Bacillus sp. SF-1. SF-1 was able to effectively extract arsenic from various arsenic-laden solids, via the reduction of solid-phase arsenate to arsenite, which is much less adsorptive than arsenate. The strain can be an easy-to-handle, and cost-effective bioremedial agent.

Arsenates↗

PubMed2003

Dissimilatory arsenate reduction by a facultative anaerobe, Bacillus sp. strain SF-1.

Bacillus sp. strain SF-1, isolated first as a selenate-reducing bacterium, was characterized as a novel arsenate-reducing bacterium. Strain SF-1 rapidly reduced 10 mM levels of arsenate to arsenite with concomitant cell growth and lactate oxidation under anoxic conditions, indicating that arsenate can act as the terminal electron acceptor for anaerobic respiration (dissimilatory arsenate reduction). Strain SF-1 can use various organic compounds including synthetic sewage mainly composed of peptone and meat extract as the electron donors for arsenate reduction. Although strain SF-1 can grow aerobically, which is very rare for dissimilatory arsenate-reducing bacteria, the presence of oxygen inhibited the arsenate reduction. On the other hand, the presence of nitrate or selenate, which can support the growth of strain SF-1 as electron acceptors, did not significantly inhibit the arsenate reduction. Arsenate-reducing activity, that is, arsenate reductase, was exhibited in strain SF-1 only when grown on arsenate, but the enzyme could not reduce other oxyanions including nitrate and selenate. It was presumed that arsenate reduction was carried out by an enzyme system separate from those of nitrate and selenate reduction, and the arsenate reductase was inducible and specific for arsenate. These results suggest that strain SF-1 may be utilized for extracting arsenic from contaminated soil for the purpose of bioremediation.

Journal Article↗