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theses

Microbe-mineral interactions are dominated by chemosynthetic microorganisms that use inorganic substrates for growth, impacting the formation and dissolution of minerals. In this dissertation, I continued to characterize Bosea sp. WAO using classical microbiological techniques and genomic analysis to better understand its physiology and ability to use inorganic electron donors for growth. This aerobic microorganism is capable of facultative chemolithoautotrophic growth on arsenite and several reduced sulfur compounds. It grows optimally at 25°C, pH 8, and is intolerant to salinity above 3.5 % w/v NaCl. Genomic analysis revealed that it contains the arsenite oxidase genes, aioA and aioB, and possesses the complete sox pathway. The draft genome is of a single circular 6,125,776 bp chromosome that contains 62 RNA genes and a predicted 5,665 protein-coding genes. A method for in situ stabilization of Pb contamination is the addition of phosphate to convert redox sensitive sulfide minerals into sparingly soluble pyromorphite. I investigated the fate of reduced sulfur during the conversion of galena [PbS] to chloropyromorphite [Pb5(PO4)3Cl] concluding with powder XRD analysis that the reaction results in the formation of elemental sulfur [S8]. Under abiotic conditions the S8 was retained in the solid phase, and negligible other sulfur species were detected in the aqueous phase. When PbS reacted in the presence Bosea sp. WAO the S8 in the secondary mineral was oxidized to sulfate and significantly more sulfate was produced from the secondary mineral than from the primary PbS. Microscopic analysis of mineral particles indicated the organism was co-localized and grew on the secondary mineral surface. The results indicate that stimulation of sulfur-oxidizing activity may be a direct consequence of phosphate amendments to Pb contaminated soils. Four microorganisms, Bosea sp. WAO, Starkeya novella, Thiomicrospira crunogena EPR75 and Halothiobacillus hydrothermailis EPR 155, unable to utilize sodium tartrate as a carbon source, were used to study chemolithoautotrophic growth on antimony, Sb(0) and Sb(III). These organisms did not grow on either elemental antimony or potassium antimony tartrate. Bosea sp. WAO’s initial rate of sulfate production from the mineral stibnite (Sb2S3) was higher than the controls, suggesting the organism increases oxidation of the mineral.

ETD_7092

Ph.D.

Includes bibliographical references

by Alexandra B. Walczak

doi:10.7282/T3BG2R54

ETD doctoral

The author owns the copyright to this work.