Journal of Industrial Microbiology and Biotechnology

, Volume 25, Issue 4, pp 198–203

Chromate reduction by Rhodobacter sphaeroides

  • B B Nepple
  • J Kessi
  • R Bachofen

DOI: 10.1038/sj.jim.7000049

Cite this article as:
Nepple, B., Kessi, J. & Bachofen, R. J Ind Microbiol Biotech (2000) 25: 198. doi:10.1038/sj.jim.7000049

Rhodobacter sphaeroides

grew in the presence of up to 43 μM chromate and reduced hexavalent chromium to the trivalent form under both aerobic and anaerobic conditions. Reduced chromium remained in the external medium. Reductase activity was present in cells of R. sphaeroides independent of whether chromate was present or not in the growth medium. The reducing activity was found in the cytoplasmic cell fraction and was dependent on NADH. The chromate-reducing enzyme was purified by anion exchange, hydroxyapatite and hydrophobic interaction chromatography, and gel filtration. The molecular weight of the enzyme was 42 kDa as determined by gel filtration. The optimum of the reaction is at pH 7.0 and 30°C. The enzyme activity showed a hyperbolic dependence on the concentrations of both substrates, NADH and chromate, with a maximum velocity at 0.15 mM NADH. A Km of 15±1.3 μM CrO42− and a Vmax of 420±50 μmol min−1 mg protein−1 was determined for the enzyme isolated from anaerobically grown cells and 29±6.4 μM CrO42− and 100±9.6 μmol CrO42− min−1 mg protein−1 for the one from aerobically grown ones. Journal of Industrial Microbiology & Biotechnology (2000) 25, 198–203.

Keywords: Rhodobacter sphaeroides; chromate reduction; cytoplasmic localization; enzyme purification

Copyright information

© Society for Industrial Microbiology 2000

Authors and Affiliations

  • B B Nepple
    • 1
  • J Kessi
    • 1
  • R Bachofen
    • 1
  1. 1.Institut für Pflanzenbiologie, Abteilung Mikrobiologie, Universität Zürich, Zollikerstr. 107, Zurich CH-8008, SwitzerlandCH