Related Experiment Videos
Stimulation of mycelial growth of Endothia parasitica by heavy metals
Abstract:
Of 16 metal cations tested on agar medium, only copper and iron stimulated mycelial growth of Endothia parasitica in relatively high concentrations. Similarly enhanced growth was produced in high (32%) glucose concentrations and also when the fungus was grown on cellophane placed over the agar surface. E. parasitica secreted large amounts of oxalate that precipitated primarily as calcium oxalate at the periphery of the fungal colony, causing an opaque halo in the medium. Mycelial growth was retarded greatly when calcium oxalate accumulated, but retardation was reversed by copper and iron salts that prevented accumulation of the calcium oxalate crystals. E. parasitica grew well on media containing copper oxalate and copper-calcium oxalate but grew poorly with calcium oxalate as the carbon source and was inhibited by sodium oxalate in the medium. The specificity by which only copper and iron salts stimulated mycelial growth suggested that the metal and oxalate ions interact to form specific oxalate complexes that reverse the inhibition of simple oxalate salts. This probably accounts for enhanced growth in the presence of otherwise toxic levels of metals and oxalate. The stimulation did not occur in liquid cultures.
Insights
Copper and iron salts stimulate Endothia parasitica growth by preventing toxic calcium oxalate accumulation. This interaction enhances fungal development on agar, but not in liquid cultures.
Area of Science:
- Mycology
- Environmental Microbiology
- Biochemistry
Background:
- Endothia parasitica, the causal agent of chestnut blight, exhibits complex nutritional requirements.
- Fungal growth can be influenced by metal ions and secreted metabolites, such as oxalates.
- Understanding these interactions is crucial for managing fungal diseases and studying fungal physiology.
Purpose of the Study:
- To investigate the effect of various metal cations on the mycelial growth of Endothia parasitica.
- To elucidate the role of oxalate secretion and calcium oxalate precipitation in growth inhibition.
- To determine the specific metal ions that can reverse oxalate-induced growth inhibition.
Main Methods:
- Agar diffusion assays with 16 metal cations and varying glucose concentrations.
- Culturing Endothia parasitica on cellophane overlays to observe colony periphery.
- Analysis of oxalate precipitation and its reversal by specific metal salts.
Main Results:
- Copper and iron ions significantly stimulated Endothia parasitica mycelial growth at high concentrations.
- Fungal secretion of oxalate led to calcium oxalate precipitation, inhibiting growth.
- Copper and iron salts reversed growth inhibition by preventing calcium oxalate accumulation, forming soluble complexes.
- Stimulatory effects were observed on agar but not in liquid cultures.
Conclusions:
- Copper and iron ions specifically interact with secreted oxalate to form complexes that promote Endothia parasitica growth.
- The precipitation of calcium oxalate is a key factor limiting fungal growth, and its reversal by specific metal ions is a novel finding.
- The differential effect between agar and liquid cultures suggests a role for surface interactions or oxygen availability in the observed phenomenon.