Aerobic microbial manufacture of nanoscale selenium: exploiting nature’s bio-nanomineralization potential

Abstract

The potential of the environment to yield organisms that can produce functional bionanominerals is demonstrated by selenium-tolerant, aerobic bacteria isolated from a seleniferous rhizosphere soil. An isolate, NS3, was identified as a Bacillus species (EU573774.1) based on morphological and 16S rRNA characterization. This strain reduced Se(IV) under aerobic conditions to produce amorphous alpha Se(0) nanospheres. A room-temperature washing treatment was then employed to remove the biomass and resulted in the production of clusters of hexagonal Se(0) nano-rods. The Se(0) nanominerals were analyzed using electron microscopy and X-ray diffraction techniques. This Bacillus isolate has the potential to be used both in the neutralizing of toxic Se(IV) anions in the environment and in the environmentally friendly manufacture of nanomaterials.

Selenobacteria selected from the rhizosphere as a potential tool for Se biofortification of wheat crops

“…The ability to accumulate Se 0 in spherical deposits in a wide variety of bacteria isolated from seleniferous soils (Ralstonia, Rhodospirillum, Stenotrophomonas, Rhodobacter, Bacillus, Sulfurospirillum and Selenihalanaerobacter) has been reported in many studies (Kessi et al 1999;Bebien et al 2001;Roux et al 2001;Dungan et al 2003). Studies have also indicated the potential of Se deposited in nanostructures for a wide variety of electronic, optical, catalytic and medical applications (Prakash et al 2010). Se 0 is a nontoxic form of Se and could be an adequate candidate for biofortification of cereal crops using bacteria as bacterial inoculation.…”

“…However, bacteria play an important role in the biogeochemical cycle of Se in nature (Haudin et al 2007;Ike et al 2000). During bacterial metabolism, Se is transformed by diverse processes (oxidation, reduction and/or methylation), and Se-tolerant bacteria (STB) have shown a great potential for use in environmental sciences (bioremediation and phytoremediation) and technology (glassware manufacturing, electronic devices) (Fesharaki et al 2010;Prakash et al 2010;Narayanan and Sakthivel 2010). Despite its potential toxicity, Se is also a recognised micronutrient with antioxidant properties, and dietary deficiencies of Se in humans can affect cancer suppression, HIV treatment, free radical-induced diseases and protection from toxic heavy metals (Fairweather-Tait et al 2010;Combs 2001).…”

Ecology and Biotechnology of Selenium-Respiring Bacteria

“…Members of both the Archaea and Bacteria domains can use selenium oxyanions (SeO 4 2Ϫ and SeO 3 2Ϫ ) as terminal electron acceptors and reduce soluble selenate and selenite to insoluble elemental selenium via dissimilatory reduction under anaerobic conditions (29). Under aerobic or microaerophilic conditions, selenium oxyanions can also be reduced to elemental selenium by various bacterial strains, through either detoxification (30) or redox homeostasis in phototrophic bacteria (31), but these are not discussed in detail in this review. Elemental selenium can be reduced further microbiologically to soluble selenide, which in combination with metal ions forms insoluble metal selenides.…”

Expulsion of selenium/protein nanoparticles through vesicle-like structures by Saccharomyces cerevisiae under microaerophilic environment

“…A few microorganisms have been well characterized for their reduction of selenite/selenate to elemental selenium under aerobic or anaerobic condition (Narasingarao and Haggblom 2007;Prakash et al 2009;Ghosh et al 2008). It was found that some microorganisms had better effect on the reduction of selenite/selenate to elemental selenium when under micro-aerobic condition (Ike et al 2000;Dungan et al 2003;Lee et al 2007).…”