Microbial metabolism of environmental chemicals to mutagens and carcinogens

Abstract

This review of the microbial metabolism of environmental chemicals to mutagens and carcinogens has led to several recommendations for optimizing the activation of some categories of chemicals in short-term test systems. Nitroreductases, azoreductases, glycosidases, esterases, and monooxygenases can be present in microorganisms. These enzyme systems are involved in the activation of chemicals to mutagens and carcinogens. Some of these enzymes are found in the indicator microorganisms of short-term test systems, and thus metabolism of chemicals by indicator microorganisms can be considered to parallel the in vivo metabolism. In vivo metabolism of chemicals by these enzyme systems is located principally in the liver and in the intestinal microflora. The metabolic potential of the indicator organisms of short-term test systems can be utilized by the choice of appropriate test procedures, e.g., use of growing cells or anaerobic treatment conditions. The metabolism of chemicals to mutagens and carcinogens by the intestinal microflora can involve enzymes that are not represented either in the indicator microorganisms utilized at present or in the in vitro activation systems consisting of liver-homogenate fractions. This deficiency in the standard test procedures can be alleviated by the use of intestinal microflora homogenates in place of the liver-homogenate fraction in in vitro activation systems.