Abstract


Lopez, Desiré, Study of the toxicity of synthetically- and biologically-produced cadmium telluride nanoparticles and an examination of the effects of S-adenosyl methionine amendment on bnf05 bacterial headspace. Master of Science (Chemistry), May, 2014, Sam Houston State University, Huntsville, Texas, 67pp. (pdf version of this thesis)

Purpose

The purpose of this research was: (1) to determine the toxicity of both synthetically- and biologically-produced nanoparticles (NPs); and (2) to determine if K2TeO3 could be reduced and methylated by a metalloid-resistant bacterium isolated from Antarctica, bnf05.

Methods

Cadmium telluride NPs were made both synthetically and biologically. Biologically-made NPs were grown under three separate growing conditions, 1) aerobic, 2) microaerobic, and 3) aerobic for the initial growth and microaerobic after the introduction of a lacZ gene inducer, to determine which condition produced the most nanoparticle fluorescence. MIC (Minimal Inhibitory Concentration) experiments were conducted on both synthetically- and biologically-made NPs for two different bacteria, BW and LHVE, using a colony counting technique.

The headspace of live cultures including the Antarctic bacterium bnf05, S-adenosyl methionine, and K2TeO3, incubated for 24 or 48 hours were analyzed via gas chromatography using solid phase microextraction.

Findings

Exciting the fluorescent biologically-made NP solutions with UV light showed that when grown in completely aerobic conditions the most fluorescent NPs were produced. The toxicity experiments for synthetically-made NPs showed that LHVE could grow in the presence of much higher NP concentrations compared to a wild type E. coli strain: an MIC of 475 mg/mL for LHVE and 35 mg/mL for BW. Through these experiments the first evidence that LHVE—known to be metalloid resistant—is also cadmium resistant was discovered. Steps were taken to determine the MICs for biologically-made NPs, but the chemicals used for lysing cells and dialyzing the NP solution back to a more neutral pH proved to interfere with MIC results. Upon using the precipitation and drying technique adopted for synthetically-produced NPs, the biologically-produced NPs were successfully isolated from their lysis and dialysis solution and this process could be used for future nanoparticle MIC determinations.

The culture headspaces of SAM (S-adenosyl methionine) and Te amended samples of bnf05 bacteria headspace showed that SAM added at two different culture concentrations could not be used to methylate the elemental tellurium produced by the bacterium to form DMTe over the 24 and 48 hr incubation periods examined.

Keywords: Quantum dots, toxicology, metalloids, Antarctic bacteria.

 

Thomas G. Chasteen
Thesis Director

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