 microbial ecology provides the link between basic biochemical and molecular studies on toxicity reduction by microbial metabolism and environmental studies that determine exposure . 
 this link provides the ability to determine which microorganisms are responsible for the actual transformations in nature , thereby establishing how predictive the laboratory pathway , kinetic , regulatory , and enzyme mechanistic information is for nature . 
 this information can be important to the rate of toxicant removal , the type and concentration of intermediate product(s ) , and the identification of conditions that limit effective toxicant removal . 
 nucleic acid - based methods now provide the main means to track important biodegrading populations . 
 examples of these methods are given that illustrate tracking a biodegrading microbe injected into an aquifer , following community succession in a toluene - degrading fluidized bed reactor , aiding the isolation from nature of novel biodegrading organisms , and rapidly characterizing the extent of microbial diversity in an aquifer stimulated to co - metabolize trichloroethene.imagesfigure 2.figure 3.figure 4.figure 5 . 
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