Grant: Discovery Grants Program - Individual

Decomposition of organic matter in the biosphere is the task of all organisms on the Earth, but ultimately degradation of the nastiest and most complex molecules falls to bacteria and fungi. While these organisms have evolved to deal with a wide variety of natural substrates, they are increasingly challenged by man-made compounds which they may or may not degrade. These degradative activities are thus of interest: to know what Nature in its incredible variety is already capable of; how and why microbes fail with man-made compounds; and how these activities might be adapted or modified to degrade chemical wastes, clean up pollutants, or transform natural materials. We are interested here in biodegradative reactions, carried out by single species of bacteria and fungi, generally to derive energy and support growth. The focus is on aerobic degradation of a limited number of simple aromatic compounds-phenols and hydroxybenzoates. These compounds form the nucleus for a wide variety of chemicals that are toxic and which cannot be degraded by humans and other higher animals. The ability of bacteria and fungi to degrade them is dependent on the action of enzymes, intracellular catalysts that specifically and efficiently direct the breakdown sequence. We are continuing our studies of selected enzymes involved in the degradation of phenols by a soil bacterium, Pseudomonas sp. strain CF600, which was originally isolated from activated sewage sludge. The first and last enzymes of the pathway are particularly interesting as they require several proteins to work together in ways that are currently not well understood. We are also looking at a range of intracellular enzymes from a diverse group of fungi that degrade similar types of compounds. Our goal in this part of the project is to learn more about such degradative enzymes in fungi, which are less well understood than those of bacteria, but which are likely to be important in the natural environment as well as in laboratory studies.