CLONING OF NEW RHODOCOCCUS EXTRADIOL DIOXYGENASE GENES AND STUDY OF THEIR DISTRIBUTION IN DIFFERENT RHODOCOCCUS STRAINS

Four extradiol dioxygenase genes which encode enzymes active against c atechol and substituted catechols were cloned from two different Rhodo coccus strains, and their nucleotide sequences were determined. A cate chol 2,3-dioxygenase gene (edoC) was shown to be identical to the prev iously described ipbC gene from the isopropylbenzene operon of Rhodoco ccus erythropolis. Amino acid sequences deduced from the three other g enes (edoA, edoB and edoD) were shown to have various degrees of homol ogy to different extradiol dioxygenases, The EdoA and EdoB dioxygenase s were classified as belonging to the third family of type I oxygenase s and represented two new subfamilies, whereas the EdoD dioxygenase wa s a type II enzyme. Analysis of six Rhodococcus strains revealed a wid e distribution of the above dioxygenase genes. Rhodococcus sp. I1 was shown to harbour all four of the analysed dioxygenase genes. Nucleotid e sequences homologous to the edoB gene were present in all of the str ains, including R. erythropolis NCIMB 13065, which did not utilize any of the aromatic compounds analysed. The latter finding points to the existence of a silent pathway(s) for degradation of aromatic compounds in this Rhodococcus strain.