Bioavailability of selenium accumulated by selenite-reducing bacteria

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• Toxicology

Background:

• Selenium (Se) contamination is a significant environmental issue.
• Understanding selenium bioavailability is crucial for assessing its ecological impact.
• Bacterial reduction of selenite to elemental selenium (SeO) is a key transformation process.

Purpose of the Study:

• To determine the bioavailability of selenium in bacterial strains.
• To evaluate the potential of bacteria for selenium bioremediation.
• To compare the bioavailability of bacterial selenium with different forms of elemental selenium.

Main Methods:

• Culturing of Bacillus subtilis and Microbacterium arborescens in the presence of sodium selenite.
• Analysis of total selenium content and speciation in lyophilized bacterial biomass.
• Feeding experiments with chicks using bacterial selenium supplements in a low-selenium diet.
• Bioavailability assays comparing bacterial selenium, gray SeO, and red SeO (prepared with different reductants).

Main Results:

• Bacterial biomass of B. subtilis and M. arborescens contained primarily elemental selenium (SeO).
• Selenium in both bacterial strains exhibited low bioavailability (approximately 2% of selenite).
• Bioavailability of red elemental selenium (SeO) varied with preparation method, with glutathione-reduced SeO showing lower bioavailability than ascorbate-reduced SeO.

Conclusions:

• Aerobic bacteria like B. subtilis and M. arborescens can convert selenite into elemental selenium with very low bioavailability.
• These bacterial strains show promise for the bioremediation of selenium-contaminated environments.
• Bacterial selenium transformation offers a strategy to reduce selenium's ecological risk.