Biosynthesis of selenium nanoparticles by Azoarcus sp. CIB

Area of Science:

• Microbiology and Nanotechnology
• Environmental Science and Biotechnology

Background:

• Selenium nanoparticles (SeNPs) have diverse biotechnological applications, but microbial synthesis mechanisms are not fully understood.
• The Azoarcus genus, known for degrading aromatic compounds and endophytic lifestyle in rice, is explored for novel physiological traits.
• Azoarcus sp. CIB's resistance to selenium oxyanions and SeNP formation is investigated.

Purpose of the Study:

• To investigate the ability of Azoarcus sp. CIB to produce selenium nanoparticles (SeNPs) under selenite stress.
• To elucidate the molecular mechanisms underlying selenite resistance and SeNP biogenesis in Azoarcus.
• To explore the potential of Azoarcus as a biocatalyst for green SeNP synthesis.

Main Methods:

• Anaerobic cultivation of Azoarcus sp. CIB in the presence of selenite.
• Electron microscopy and X-ray spectroscopy for SeNP characterization.
• Analysis of cellular responses during stationary phase and starvation conditions.

Main Results:

• Azoarcus sp. CIB is the first reported Azoarcus member to grow anaerobically with selenite, producing spherical SeNPs (123 ± 35 nm).
• Selenite resistance is primarily mediated by an energy-dependent selenite exporter.
• SeNP synthesis is triggered by stationary-phase entry and starvation, involving reduction of selenite to elemental selenium.

Conclusions:

• Azoarcus provides a novel, eco-friendly system for producing spherical SeNPs.
• This is the first report of a rice endophyte capable of SeNP production.
• Azoarcus's combined abilities in aromatic compound degradation and SeNP synthesis position it for sustainable agriculture and bioremediation.