The influence of mercury on the antioxidant enzyme activity of rumen bacteria Streptococcus bovis and Selenomonas ruminantium

Studies were undertaken to investigate the activity response of the antioxi dant enzymes superoxide dismutase (SOD), glutathione peroxidase (GSHPx), gl utathione reductase (GR) and mercury reductase (MR) of rumen bacteria Strep tococcus bovis and Selenomonas ruminantium following exposure to HgCl2. SOD activity of S. bovis which was considered as Mn-SOD increased when incubat ed with 5 mu g Hg2+ ml(-1) in anaerobic or aerobic conditions. A significan t increase in the aerobic activities of GSHPx, GR and MR was observed in th e presence of Hg2+. The anaerobic activities of these enzymes were unchange d and increased production of thiobarbituric acid reactive substances was o bserved. S. ruminantium was tolerant to 10 times higher concentrations of H g2+ than S. bovis. As a reduction of GSHPx, GR and MR activities after expo sure to Hg2+ was observed, we assume that the production of sulfides preven ted the toxic effect of mercury on this bacterium. (C) 1998 Federation of E uropean Microbiological Societies. Published by Elsevier Science B.V. All r ights reserved.