Growth inhibition of the filamentous fungus Aspergillus nidulans by cadmium: an antioxidant enzyme approach

Abstract

The heavy metal cadmium is very toxic to biological systems. Although its effect on the growth of microorganisms and plants has been investigated, the response of antioxidant enzymes of Aspergillus nidulans to cadmium is not well documented. We have studied the effect of cadmium (supplied as CdCl(2)) on catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR). 0.005 mM CdCl(2) had a very slight stimulatory effect on the growth rate of A. nidulans, but at concentrations above 0.025 mM, growth was totally inhibited. The accumulation of Cd within the mycelium was directly correlated with the increase in the concentration of CdC(2) used in the treatments. Although a cadmium-stimulated increase in SOD activity was observed, there was no change in the relative proportions of the individual Mn-SOD isoenzymes. Higher concentrations of CdCl(2) induced a small increase in total CAT activity, but there was a major increase in one isoenzymic form, that could be separated by gel electrophoresis. GR activity increased significantly following treatment with the highest concentration (0.05 mM) of CdCl(2). The increases in SOD, CAT, and GR activities suggest that CdCl(2) induces the formation of reactive oxygen species inside the mycelia of A. nidulans.

An Investigation on Tolerance and Biosorption Potential of Aspergillus awamori ZU JQ 965830.1 to Cu(II)

“…Comparable results were also obtained (Guelfi et al, 2003;Ban et al, 2012 andChakraborty et al, 2012).…”

“…This in turn leads to a more free flow of nutrients within cells and thus metabolic activity increases (Babich &Stotzky, 1980 andAhonen-Jounarth et al, 2004). Guelfi et al (2003) suggested that the higher concentrations of Cd(II) induced the autolysis of the A. nidulans mycelium, with subsequent proteolytic breakdown and reduction in the protein content. …”

“…An increase in POD and PPO activities indicateed that there was an effort on part of the fungus to minimize or neutralize the hazardous effect of ROS generated by Cu(II) treatment and that accumulation in the mycelium is required to induce the observed changes. The gradual decrease of enzyme activity suggests that the generated ROS caused irreversible oxidative damage in the fungal cell and inhibited POD activity (Guelfi et al, 2003).…”

“…Glutathione reductase (GR) also can remove H 2 O 2 and maintains a balance between reduced glutathione (GSH) and oxidized glutathione (GSSG), as the latter is toxic to cells (Guelfi et al, 2003). Activity of GR in A. awamori gradually increased by treatment with low concentrations of Cu(II) (Fig.…”

“…concentrations (Guelfi et al, 2003). However, Cu(II) is toxic to most organisms at elevated concentrations, largely through enzyme inhibition and oxidation of membrane components as a result of the ability of Cu(II) to generate toxic hydroxyl radicals (Melo et al, 2004).…”