Anaerobic degradation of 2,4,6- trinitrotoluene (TNT): molecular analysis of active degraders and metabolic pathways

Nitroaromatic compounds have been historically used as dyes, explosives and pesticides. The disposal of these products has caused widespread contamination of both soil and groundwater. 2,4,6-trinitrotoluene (TNT) has been known as the worst of these contaminants because of the mutagenic properties of the compound, its persistence in the environment, and the wide range of sites that are contaminated with TNT. It is not only harmful to humans but it is also harmful to organisms in the lower trophic levels of ecosystems, and can affect the primary production of phytoplankton in the oceans. The following series of experiments looks to determine ways that 2,4,6-trinitrotoluene could be biologically degraded in contaminated anaerobic environments. The experiments use dilution culturing, molecular techniques, and chemical analysis. Cultures were made from 3 different geographical sites (Arthur Kill, Norfolk Harbor, and an unexploded ordnance site in Hawaii) under both sulfidogenic and methanogenic conditions. The experiments demonstrate that there are bacteria present in the environment that could degrade TNT and the use of stable-isotope probing (SIP) in dilution cultures allowed the bacteria that are able to initially degrade TNT to be identified. The stable-isotope fed dilution cultures produced samples that were used for chemical analysis to determine pieces of the biological degradation pathway. These experiments determined that 1) there are bacteria that are able to utilize both the carbon and/or nitrogen present in TNT for growth and 2) toluene, methylphloroglucinol, benzoate or a benzoate derivative, and a cresol are all metabolites of anaerobic TNT degradation.Ph.D.Includes bibliographical references.by Erin Maureen Gallaghe