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

Abstract

The increase of Mg2+, from 1.3 to 3 µM, in growth medium of F. equiseti and F. acuminatum increased intracellular magnesium levels from 0.83 and 0.81 µM to 1.75 and 1.42 µM 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 µM Mg2+ culture medium were 0.67 and 1.23 µM, while maximum iron levels were determined to be 1.3 µM Mg2+ as 0.51 and 0.29 µM, 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 µM 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.