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theses

Anaerobic microbes are integral to the fate of organic contaminants in the environment. Polyaromatic pollutants are regularly found in anoxic environments, including wastewater treatment and subsurface sediments. In this dissertation, I combine microbial and chemical techniques to understand how microorganisms metabolize aromatic contaminants in anoxic marine sediment and anaerobic wastewater treatment. The first substrate described is naphthalene, the model polycyclic aromatic hydrocarbon (PAH) that established the field of anaerobic PAH degradation. Stable isotope probing of a new sulfidogenic naphthalene degrading culture revealed two organisms responsible for initial naphthalene degradation and a third probable initial naphthalene degrader. Two were closely related to the known isolated anaerobic naphthalene degraders, while the third was distantly related to its closest described organism. This third organism likely represents a new taxon of naphthalene degraders. Using classic anaerobic enrichment techniques, I also enriched for communities able to transform the pharmaceuticals naproxen and diphenhydramine. Unlike naphthalene, however, microbes did not mineralize the pharmaceutical substrates to CO2. Rather, microbes removed the methyl substituent, leaving demethylated metabolites. These accumulated in culture with no further metabolism of the carbon skeleton. Naproxen was readily O-demethylated by microbes in both methanogenic wastewater and marine sediment. Community analysis of each culture illustrated the heterotrophic communities enriched during demethylation. In the methanogenic naproxen culture, bacterial and archaeal sequencing revealed a three-tiered trophic transfer of the methyl carbon from acetogens to syntrophic acetate oxidizing bacteria/methanogens. In the marine naproxen transforming culture, a diverse fermentative community was enriched. The microbial community in the wastewater diphenhydramine culture was also enriched for fermenting organisms. In all cultures, the removal of the methyl substituent supported heterotrophic microbial communities. As seen in naproxen, the phenylmethyl ether structure is also abundant in many other pharmaceuticals and personal care products (PPCPs). Because of this, I also examined the ability of the methanogenic and marine naproxen cultures to O-demethylate diverse PPCPs. Both marine and methanogenic naproxen enrichments O-demethylated oxybenzone, guaifenesin, and methylparaben. We thus propose that in anoxic environments, phenylmethyl ether contaminants will be demethylated, and the desmethyl metabolites will comprise a critical portion of total contaminants. Systematic phenylmethyl ether O-demethylation can be extrapolated to a variety of PPCPs, with unknown ecosystem impacts.

ETD_7886

Ph.D.

Includes bibliographical references

by Sarah J. Wolfson

doi:10.7282/T3930X3F

ETD doctoral

The author owns the copyright to this work.