Volatilization of Selenium by Alternaria alternata

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Ecotoxicology

Background:

• Seleniferous water poses ecological risks in California's Central Valley.
• Evaporation ponds accumulate selenium (Se) to concerning levels (0.005–5 mg/L).
• Understanding microbial selenium methylation is crucial for remediation strategies.

Purpose of the Study:

• Isolate selenium-methylating microorganisms from evaporation pond water.
• Determine environmental factors influencing microbial selenium methylation.
• Assess the potential for bioremediation of seleniferous water.

Main Methods:

• Isolation and identification of Se-methylating organisms.
• Enrichment cultures and manipulation of growth parameters (pH, temperature).
• Analysis of volatile selenium compounds produced by isolated organisms.

Main Results:

• Alternaria alternata was identified as a potent Se-methylating fungus.
• Dimethylselenide was identified as the primary volatile selenium product.
• Optimal methylation occurred at pH 6.5 and 30°C, with selenate and selenite being preferred substrates. Methyl donors like l-methionine and methyl cobalamine enhanced dimethylselenide production.

Conclusions:

• Selenium-methylating microbes, including A. alternata, are active in evaporation pond environments.
• Microbial volatilization of selenium as dimethylselenide is a significant process.
• Optimizing environmental conditions could enable *in situ* selenium removal from contaminated waters.