S23: Novel Metabolic Diversity Involved in Biodegradation of Natural Nitro Compounds

Synthesis and degradation of the countless small organic compounds produced in the biosphere requires a huge metabolic diversity that is only beginning to be explored. The goal of our work is to discover new metabolic diversity by exploring the metabolism of natural nitrogenous compounds selected on the basis of unusual structural features or ecological roles. Previous research on biodegradation of nitro and amino compounds has focused on widely used synthetic chemicals and explosives because of their potential as pollutants. Thus a great deal is known about the catabolic pathways that evolved in response to their recent introduction into the biosphere. In contrast, little is known about the degradation of over 200 natural nitro compounds found in microbes, plants, and animals. Such compounds include all of the functional groups found in the common explosives. We have isolated bacteria able to degrade natural nitro compounds including 3-nitrotyrosine, 5-nitroanthranilic acid, 2-nitroimidazole and 3-nitropropionic acid. In each case novel enzymes and genes are involved in the elimination of the key functional groups which might explain the existence of many of the unknown genes revealed by metagenomics. Exploration of the catabolic pathways for natural compounds provides insight about how pathways evolve and reveals genes that can be exploited for applications in biodegradation and biocatalysis. Because natural metabolic diversity provides the basis for evolution of catabolic pathways for degradation of synthetic organic molecules released into the environment, an enhanced understanding of the metabolic capabilities of natural microbes should enable the design of more environmentally benign explosives.