Nanoparticles with a diameter of 0-100 nm display unique physical and chemical properties. Although elemental selenium (Se) is generally not water soluble and thus, not bioavailable, our previous studies showed that nanoscale elemental Se particles (SeNPs) can be absorbed and volatilized by soil bacterial Pseudomonas fuscovaginae that was isolated from a Se hyperaccumulator plant Stanleya pinnata, which is significantly higher than bulk/non-nanoscale elemental Se. However, it is not clear if elemental SeNPs have been bio-transformed by P. fuscovaginae and how much Se from SeNPs have been accumulated internally in bacterial cells compared to the amount of Se adsorbed or deposited on bacterial cell surfaces. To answer these specific research questions, this laboratory study applied chemically synthesized elemental SeNPs to the bacterial cultural solution, and used the synchrotron-based X-ray Absorption Near-edge Structure Spectroscopy (XANES) to determine potential Se chemical form changes derived from the bacterial strain. Atomic Force Microscopy (AFM) was used to observe SeNPs adsorbed on bacterial cell surfaces under natural (i.e., no sample fixation and dehydration) and ambient conditions, while Scanning Electron Microscopy (SEM) coupled with Energy-dispersive X-ray spectroscopy (EDX) was used to characterize Se adsorbed on the surface of the bacterium. Research findings from XANES showed that the soil bacterium was able to biotransform SeNPs into organic forms of Se, including ∼67.5% of methyl-selenocysteine (MeSeCys), ∼15.5% selenocysteine (SeCys), along with small portions of selenate and selenite (~8% each) in the bacterial cultural solution. However, the dominant chemical form of Se with the bacterial cells was elemental Se (SeNPs). AFM and SEM observation supports the attachment of particulate deposits on the bacterial cell surface.
|Commitee:||McCraken, Vance, Rowland, Kevin, Voss, Eric J.|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 57/01M(E), Masters Abstracts International|
|Subjects:||Biology, Chemistry, Environmental science|
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