New dioxygenase from metagenomic library from Brazilian soil: insights into antibiotic resistance and bioremediation.

OBJECTIVES: Putative new dioxygenases were identified in a metagenomic ß-lactam-resistance screening and, given their key role on aromatic metabolism, we raise the hypothesis that these enzymes maybe concomitantly related to antibiotic resistance and aromatic degradation. RESULTS: ORFs of three putative dioxygenases were isolated from resistant metagenomic clones. One of them, CRB2(1), was subcloned into pET24a expression vector and subjected to downstream phenotypic and bioinformatics analyses that demonstrated the "dual effect" of our metagenomic dioxygenase, on antibiotic and aromatic resistance. Furthermore, initial characterization assays strongly suggests that CRB2(1) open-reading frame is an extradiol-dioxygenase, most probably a bicupin domain gentisate 1,2-dioxygenase. This observation is, to our knowledge, the first description of a metagenomic dioxygenase and its action on ß-lactam resistance. CONCLUSION: Unraveling the diversity of antibiotic resistance elements on the environment could not only identify new genes and mechanisms in which bacteria can resist to antibiotics, but also contribute to biotechnology processes, such as in bioremediation.