Molecular and Cellular Fundamentals of Aerobic Cometabolism

Abstract : Aerobic cometabolism recognizes that microorganisms can transform non-growth supporting substrates. The term cometabolism was first introduced over 30 years ago and has been redefined, criticized, and used widely ever since. In this review we have examined the cometabolism of chlorinated solvents. These transformations are initiated by monooxygenases or dioxygenases with relaxed substrate ranges. The physiological role of the monooxygenases is to initiate the metabolism of growth substrates which are most often hydrocarbons. A metabolically and structurally diverse set of enzymes catalyze oxidative reactions with chlorinated solvents. Common growth-supporting substrates include methane, propane, toluene, ethylene and ammonia. The transformation of chlorinated solvents by these enzymes presents the cell with a new set of compounds. Some of these compounds are toxic to the cells, others are stable products which are expelled from the cell and in a few cases, the products are utilized by the cells. Production of most of the enzymes with potential for degradation of chlorinated solvents is induced by the presence of the growth-supporting substrate. In some cases, chlorinated aliphatics will also induce production of the enzyme. Cometabolism can have a profound influence on a cell.