Microbial catabolism, the carbon cycle and environmental pollution.

The establishment of a carbon cycle was a necessary prerequisite for the evolution of higher forms of life. This could not have been achieved without the direct participation of oxygen gas in certain metabolic reactions. The controlled activation of oxygen is catalyzed by microbial oxygenases; in principle, activated oxygen is hazardous to all living forms but without it, the degradative segment of the carbon cycle could not operate. The degradation of aromatic compounds is not an esoteric activity of a few specialized microorganisms. It occurs continuously, accompanied by fixation and cycling of oxygen on a massive scale; but like other global biochemical processes it tends to be neglected in general biological curricula. However, knowledge of the scope and limitations of microbial catabolic enzymes is central to the development of rational approaches to many of society's environmental concerns.