Ohe. Hammouda, SUPEROXIDE-DISMUTASE LEVEL IN RESPONSE TO PARAQUAT AND HIGH-TEMPERATURE IN THE CYANOBACTERIUM GLOEOCAPSA SP, Biologia plantarum, 36(2), 1994, pp. 229-236
Paraquat (methylviologen) at concentrations above 0.05 mM inhibited th
e growth of photoautotrophic cyanobacterium Gloeocapsa sp. in axenic c
ultures. The growth rate was not affected by concentrations of 0.01 mM
or less. This concentration resulted after a lag period in a moderate
increase in superoxide dismutase level. After removal of paraquat, th
e cyanobacterium continued to generate higher levels of superoxide dis
mutase. There was a lag period of one hour before resumption of normal
enzyme activity. Addition of puromycin at concentration of 0.5 mg cm-
3 had no effect on cell survival, but greatly enhanced the sensitivity
of the culture to the toxicity of paraquat. The data showed an increa
se of SOD activity by temperatures above the normal growth temperature
level. However, this increase was suppressed by chloramphenicol which
revealed that the induction of superoxide dismutase by high temperatu
res was associated with de novo protein synthesis.