A comparative study of the metal ion uptake and antioxidant enzyme activities of Fusarium equiseti and Fusarium acuminatum as a function of external magnesium concentration

The increase of Mg2+, from 1.3 to 3 mu M, in growth medium of F. equiseti and F. acuminatum increased intracellular magnesium levels from 0.83 and 0.81 mu M to 1.75 and 1.42 mu M on the 12th day, respectively. Intracellular magnesium levels also elevated depending upon the number of incubation days. The maximum manganese levels of F. equiseti and F. acuminatum obtained in 1.6 mu M Mg2+ culture medium were 0.67 and 1.23 mu M, while maximum iron levels were determined to be 1.3 mu M Mg2+ as 0.51 and 0.29 mu M, respectively. The maximum intracellular iron and manganese levels were decreased significantly with increasing Mg2+ concentration in the culture medium and were increased depending upon the incubation period. However, intracellular zinc levels of these strains didn't change with Mg2+ concentration and incubation period. The maximum superoxide dismutase (MnSOD) activities of F. equiseti and F. acuminatum, related to increased intracellular manganese levels up to 1.6 mu M Mg2+ in growth medium, were determined to be 78 and 110 IU/mg, respectively. CAT activity variations showed agreement with SOD activity and reached a maximum at 320 and 225 IU/mg under the same conditions. The minimum LPO levels of the Fusarium strains with the maximum MnSOD and CAT activities were determined as 1.2 and 0.9 nmol MDA/g., wet weight. The higher LPO level of F. equiseti grown at the same condition, in spite of 1.42-fold higher CAT activity due to the 1.41-fold lower SOD activity, as well as a 2.0-fold higher iron level, indicated increases in the generation of reactive oxygen species Via the Fenton reaction.