Stress reactions in cyanobacteria lacking antioxidant genes

  • I. R. Fomina
  • V. D. Kreslavski
  • T. I. Balakhnina
  • S. M. Hertz
  • A. A. Ivanov
  • A. A. Kosobryukhov
  • V. Yu. Lyubimov
  • G. N. Nazarova
  • K. Y. Biel

Abstract

Aims. To improve understanding of the roles of antioxidant genes in phototrophic cells the effects of 0,5µM methyl viologen (MV) on the sodB- mutant of Synechococcus sp. PCC 7942 and the katG- mutant of Synechocystis sp. PCC 6803 were examined. Methods. Cultures were grown in liquid BG11 medium at 30 µE m-2 s-1. Results. 0,5 µM MV inhibited growth and photosynthetic activity in the sodB- mutant within 8 hr. The PCC 7942 wild type as well the PCC 6803 wild type and its katG-mutant remained nearly unaffected for 48 hr. The oxidative damage to the sodB- mutant was not accompanied by essential changes in pigment content but was accompanied by greater catalase activity. Conclusions. Lack of catalase activity in the katG- mutant of Synechocystis sp. PCC 6803 does not sensitize to MV because iron superoxide dismutase (Fe-SOD) is active. However, if the Fe-SOD is absent, as in the Synechococcus sp. PCC 7942 sodB- mutant, activation of catalase appears to be an adaptive response to MV that may allow survival.

Key words: Synechococcus sp. PCC 7942, Synechocystis sp. PCC 6803, methyl viologen.