Evolution of atrazine-degrading capabilities in the environment.

Since their first introduction in the mid 1950s, man-made s-triazine herbicides such as atrazine have extensively been used in agriculture to control broadleaf weed growth in different crops, and thus contributed to improving crop yield and quality. Atrazine is the most widely used s-triazine herbicide for the control of weeds in crops such as corn and sorghum. Although atrazine was initially found to be slowly and partially biodegradable, predominantly by nonspecific P450 monoxygenases which do not sustain microbial growth, microorganisms gradually evolved as a result of repeated exposure, started using it as a growth substrate and eventually succeeded in mineralizing it. Within three decades, an entirely new hydrolase-dependent pathway for atrazine mineralization emerged and rapidly spread worldwide among genetically different bacteria. This review focuses on the enzymes involved in atrazine mineralization and their evolutionary histories, the genetic composition of microbial populations involved in atrazine degradation and the biotechnologies that have been developed, based on these systems, for the bioremediation of atrazine contamination in the environment.