With the environmental problems caused by man-induced pollution by persistent toxic compounds, the importance of finding remediation solutions is immense. As an emerging field, microbial environmental biotechnology may provide the tools to achieve novel solutions. Microbial communities in the environment have biodegradation capacities which could be, and historically have been, exploited for bioremediation. The novelty lies in being able to access the capacity of the uncultured majority of the microbial community. Every day, more and more knowledge is gained in the field and thanks to new approaches such as metagenomics, along with the access to databases and archives where scientists share information and data, the quest becomes considerably facilitated. Microorganisms are highly diverse in metabolic pathways and some have become highly developed during evolution; detoxification and biotransformation of naturally occurring toxic compounds are therefore not novel concepts. The environmental problem occurs when synthetically manufactured compounds are less efficiently biodegraded. However, improved knowledge about the degradation potential in nature and the involved enzymes may help in developing bioremediation procedures. For this reason, an enzyme involved in catabolic pathways of chlorinated aromatic compounds, dienelactone hydrolase, which has been less well studied, was selected as a target. This study investigated the biogeographical distribution of the dienelactone hydrolase gene identified in metagenomes sampled from different environments globally in order to detect potential environmental patterns. Results may cast light on its significance for degradation of chlorinated aromatic compounds in nature. The results indicate a broad biogeographical distribution of dienelactone hydrolase in varying microbial habitats in the environment. The enzyme was found in environments ranging from water and soil habitats to hypersaline-, dechlorinating-, hot-spring- and other extremophillic habitats, in which the gene sequences shared high similarity within each group. A broad environmental distribution suggests that dienlactone hydrolase could be useful in bioremediation.

The clcD gene encoding dienelactone hydrolase (DLH) is part of the clc gene cluster for the utilization of the B-ketoadipate pathway intermediate chlorocatechol. The roles that individual amino acids residues play in catalysis and binding of the enzyme were investigated. Using PCR a 1.9 kbp clcD fragment was amplified and subcloned yielding a 821 bp BamHi to ZscoRI subclone in the plasmid pUC19.