The Haloalkane Dehalogenase Genes DHLA and dhaA are Globally Distributed and Highly Conserved

Abstract

Direct hydrolytic dehalogenation by haloalkane dehalogenases is the most important mechanism involved in biodegradation of synthetic haloalkanes that occur as soil pollutants. Here we show that five Gram-negative 1,2-dichloroethane-utilizing bacteria contain haloalkane dehalogenase genes identical to the dhlA gene from Xanthobacter autotrophicus GJ10, whereas five Gram-positive chloroalkane degraders, independently isolated from geographically distinct locations, contain genes identical to the dhaA gene of Rhodococcus rhodochrous NCIMB13064. Furthermore, the dhaA gene was detected by PCR amplification in fifteen newly isolated Gram-positive chloroalkane-degrading bacteria. Our results suggest that the dhlA and dhaA genes recently arose from a single origin and have become distributed globally, most likely as the result of the massive and worldwide use of synthetic chlorinated hydrocarbons in industry and agriculture.