Date of Award:

5-2013

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Committee Chair(s)

Anne J. Anderson

Committee

Anne J. Anderson

Committee

Dennis L. Welker

Committee

Jeanette M. Norton

Committee

Ronald C. Sims

Committee

Charles D. Miller

Abstract

Polycyclic aromatic hydrocarbons are produced from incomplete combustion of organic materials by human or natural activities. These polycyclic aromatic hydrocarbons are classified as pollutants because of their toxic, mutagenic, and carcinogenic characteristics. Mycobacterium sp. strain KMS, isolated from a contaminated soil, grows on the model polycyclic aromatic hydrocarbon, pyrene, with its degradation to water and carbon dioxide. This study locates genes on the chromosome and plasmids of isolate KMS relating to pyrene degradation, elucidates the influence of other carbon sources available in the habitats of isolate KMS on degradation of pyrene, and deduces possible metabolic pathways used by isolate KMS for its survival.

Pyrene-degrading genes are clustered on the KMS chromosome. Duplication of some of the genes may help the degradation of pyrene by KMS in contaminated soils. Pyrenedegrading genes are clustered and are in similar positions in the genome of six pyrenedegrading Mycobacterium isolates. Those genes were possibly acquired from a common ancestor.

Isolate KMS also grows on a simple aromatic compound, benzoate. The presence of benzoate does not help pyrene degradation by inducing the pyrene-degrading genes. Also the presence of carbon sources typical of those in the rhizosphere, such as sugars, organic acids, and benzoate, delayed utilization of pyrene until these carbon sources were utilized. Benzoate did not repress growth on the sugars or organic acids.

Analysis of gene transcription and enzyme activities revealed that isolate KMS had novel pathways for interconversion of carbon compounds required for effective cell growth, especially for the structures required for the thick cell wall of the mycobacteria.

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