to constituents that are then incorporated into central metabolic pathways (Sutherland and others 1995; Figure 1).

An important point is that the key enzymes that activate this very stable bicyclic molecule—the dioxygenases—require molecular oxygen as a reactant. Oxygen therefore must participate in the reaction to activate the rings or to catalyze the ring fission that occurs here. Salicylic acid requires an oxygenase to break the ring. Hence, oxygen is a reactant.

In the typical known pathway for alkane degradation, which produces fatty acids that can then be incorporated into basic metabolic processes, monooxygenases are required. Again, oxygen is one of the reactants in the reaction that forms fatty acids.

The preceding description sets the stage. In the aerobic environment, we have organisms that require the activity of oxygenases; and in an anoxic environment, where oxygen is not present, let us consider what happens. If anything happens, it must occur through a significantly different biochemical and metabolic mechanism. That area is where I have involved my students, showing them that we can find these organisms because we know they are there. We know they can carry out certain novel degradation reactions, but we do not yet know whether this process is relevant to the environment.

The anaerobic organisms found in that large reservoir of anoxic sediment do not use oxygen but can use other inorganic electronic acceptors