Date of Award

Spring 1986

Project Type

Dissertation

Program or Major

Microbiology

Degree Name

Doctor of Philosophy

Abstract

Using radiorespirometric, spectrophotometric and high performance liquid and thin layer chromatographic methods, the degradation and intermediary metabolism of the polycyclic aromatic hydrocarbon (PAH), phenanthrene, by estuarine enrichment and pure microbial cultures was examined.

A Mycobacterium species, strain BG1, able to use phenanthrene as sole carbon and energy source, was isolated from estuarine sediment. Phenanthrene degradation proceeded via the intermediates, 1-hydroxy-2-naphthoic acid (1H2NA) and protocatechuic acid. However, unlike other phenanthrene-degrading cultures, aromatic intermediates, including 1H2NA, did not accumulate. Consistent with the induction of meta pathway enzymes in phenanthrene-grown BG1 cells, phenanthrene degradation was stimulated in pyruvate-supplemented cultures (an end product of meta cleavage) and repressed in succinate-supplemented cultures (an end product of ortho cleavage). Phenanthrene-degrading cells possessed 3 plasmids (20.6, 57.5 and 76.7 megadaltons) likely responsible for degradation. Plasmids and the phenanthrene-degrading phenotype were absent in nutrient-grown cells.

Analogous to degradative reactions involving other PAH when present in excess, enrichment cultures and cultures of most isolates derived from them accumulated near stoichiometric amounts of 1 H2NA during phenanthrene degradation. In pure cultures, 1 H2NA was not further degraded. In enrichment cultures, subsequent mineralization of 1 H2NA led to secondary increases in biomass. Two-stage mineralization of phenanthrene was also evidenced by a biphasic ('14)CO(,2) production in enrichment cultures spiked with low concentrations (0.5 mg L('-1)) of ('14)C-phenanthrene. Here, however, polar metabolites comprised less than 10% of the total initial activity.

Phenanthrene-degrading bacteria were ubiquitous in the waters and sediments of the Great Bay Estuary, NH, and activities correlated positively with the degree of previous exposure to PAH. Particularly active were sediments collected near an oil refinery and water samples collected downstream from a dredging operation. Coal tar-derived PAH, analyzed in dredge and downstream sediments by capillary gas chromatography, were introduced into the river in high concentrations over several months. Phenanthrene degradation potentials were also high in areas influenced by pleasure and commercial boating activities. Surface microlayer samples from marinas were enriched with fluorescent hydrocarbons but often showed depressed phenanthrene degradative activities relative to underlying bulk waters. Sunlight, hydrocarbons or organotin compounds were possibly inhibitory.

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