Effects of microcystin-RR on the antioxidant system of Bacillus subtilis

Microcystins are a kind of cyclic hepatotoxins produced by many cyanobacterial species. Many works have been done concerning, the toxic effects of microcystins on animals and plants. However, the reports about their effects on microbial cells are very limited. In the present paper, Bacillus subtilis (B. subtilis) was used to determine the dose- and time-effect of microcystin-RR, and the results showed that the activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) was significantly increased to that of control, when exposed to 5 or 10 mu g/ml microcystin-RR for 1 h. The contents of thiobarbituric acid-reactive sub-stances (TBARS) and glutathione (GSH) as well as glu-tathione reductase (GR) activity were obviously increased only when exposed to 10 mu g/ml microcystin-RR. For the time-effect of microcystin-RR on B. subtilis, the activities of antioxidant enzymes including SOD and CAT as well as GR activity and TBARS, GSH contents in B. subtilis were at first significantly increased, and then subsequently de-creased. These results suggested that microcystin-RR could induce the oxidative stress of B. subtilis for a short period. The antioxidant system protects B. subtilis from oxidative damage.

Microcystins are a kind of cyclic hepatotoxins produced by many cyanobacterial species. Many works have been done concerning, the toxic effects of microcystins on animals and plants. However, the reports about their effects on microbial cells are very limited. In the present paper, Bacillus subtilis (B. subtilis) was used to determine the dose- and time-effect of microcystin-RR, and the results showed that the activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) was significantly increased to that of control, when exposed to 5 or 10 mu g/ml microcystin-RR for 1 h. The contents of thiobarbituric acid-reactive sub-stances (TBARS) and glutathione (GSH) as well as glu-tathione reductase (GR) activity were obviously increased only when exposed to 10 mu g/ml microcystin-RR. For the time-effect of microcystin-RR on B. subtilis, the activities of antioxidant enzymes including SOD and CAT as well as GR activity and TBARS, GSH contents in B. subtilis were at first significantly increased, and then subsequently de-creased. These results suggested that microcystin-RR could induce the oxidative stress of B. subtilis for a short period. The antioxidant system protects B. subtilis from oxidative damage.