Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

published_or_final_version / abstract / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Thesis (doctoral)--University of Helsinki, 2007. / Includes bibliographical references. Also available on the World Wide Web.

No description available.

Thesis (M.Sc.) -- Memorial University of Newfoundland. 1976. / Typescript. Bibliography : leaves 137-148. Also available online.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Mycobacterium vaccae JOB5 and Graphium sp. were studied to evaluate their ability to cometabolize methyl tert-butyl ether (MTBE) and its metabolites after growth on two different alkanes, propane and iso-pentane. Both cultures were capable of cometabolizing MTBE and the metabolites, tert-butyl formate (TBF) and tert-butyl alcohol (TBA). MTBE, TBF, and TBA did not support growth of either microbe. Higher degradation rates were obtained in the bacterial system when the cultures were grown on iso-pentane. Nonlinear least squares regression and direct linear plot methods were used to estimate kinetic coefficients and provided comparable results. The enzymes from Mycobacterium vaccae JOB5 and Graphium sp. that promote the cometabolism of MTBE and its metabolites exhibited similar kinetics and substrate inhibition. The presence of the substrate decreased the degradation rate of MTBE and TBA suggesting competitive inhibition and preference for the substrate. Blockage experiment with acetylene suggested the presence of an alkane monooxygenase for the metabolism of MTBE and TBA, and a hydrolytic enzyme for the degradation of TBF. The presence of a hydrolase enzyme was supported by the fact that TBF was degraded to TBA under either aerobic or anaerobic conditions and was not inhibited by the presence of acetylene, propane, or isopentane. Measured rates of abiotic hydrolysis of TBF were significantly less than biodegradation rates. Acetylene acted as a reversible inhibitor for both cultures when tested in the presence of the growth media and as an inactivator when tested in the presence of a phosphate solution for the bacterial system. Growth-batch reactor experiments were conducted to compare the degradation of iso-pentane and MTBE with the predicted degradation rates based upon kinetic constants determined from single and dual-compound experiments. Experimental data was modeled with Monod kinetics and STELLA�� software. Reasonable predictions of reactor performance were achieved when Monod maximum utilization rates were increased compared to single and dual-compound experiments. / Graduation date: 2002

The relative role of cospeciation and host switching in the phylogenetic history of ascomycete foliar symbionts is addressed in the orders Leotiales and Rhytismatales, fungi associated predominantly with Pinaceae (Coniferales). Emphasis is placed on comparing the evolution of the sister genera Pseudotsuga and Larix (Pinaceae) with that of the pathogenic and endophytic fungi in the genus Rhabdocline. Pinaceae evolved during the Mesozoic and divergence of all extant genera and several infrageneric lineages (esp. in Pinus) occurred prior to the Tertiary, with subsequent species radiations following climatic changes of the Eocene. The youngest generic pair to evolve from Pinaceae, Larix and Pseudotsuga, diverged near the Cretaceous-Tertiary boundary in East Asia or western North America. Rhabdocline is comprised of seven species and subspecies, six known from two species of Pseudotsuga and one, the asexual species Meria laricis, from three species of Larix. Evidence from host distributions and from nuclear ribosomal DNA suggests that Rhabdocline speciated in western North America and has been involved in several host switches. The ancestor of Meria laricis appears to have switched from P. menziesii to its current western North American hosts, L. occidentalis, L. lyallii, and very recently may have extended its host range to the European species, L. decidua. The occurrence of two lineages of R. weirii ssp. weirii on both North American species of Pseudotsuga is also probably the result of a recent host switch. Evidence of hostmediated divergence is seen in R. parkeri, which has different internal transcribed spacer types in the geographically isolated coastal and interior forms of P. menziesii. The wide host ranges of fungal genera closely related to Rhabdocline indicates that host switching is a prevalent pattern in the evolution of foliar symbionts in Leotiales and Rhytismatales. The prevalence of host switching in this group relative to other endosymbiotic organisms can probably be attributed to differences in dispersal mechanisms. Spores of foliar fungi are dispersed horizontally by wind and rain, rather than vertically from parent to offspring. Over evolutionary time, this provides more opportunities to shift to new hosts, particularly when the hosts are closely related and have overlapping distributions. / Graduation date: 1998