First report on the kinetic characterization of a metagenome-derived metallo-b-lactamase

M. M. RODRÍGUEZ; B. GHIGLIONE; L. MOE; J. DI CONZA; FEDERICO JAVIER WOLMAN; E. BLATEZKY; J. HANDELSMAN; G. GUTKIND; P. POWER

Leipzig

Congreso; FEMS 2013. 5 Congress of european microbiologists; 2013

Federation of European Microbiological Societies

Background: It is well known that some prevalent β‐lactamase‐encoding genes were recruited from the chromosome of environmental species, disseminated to pathogens and became a major clinical problem. Metagenomics has been successfully used for screening antimicrobial resistance genes for different families of antibiotics from environmental soil samples, including β‐lactamaseencoding genes. Objectives: We performed the biochemical characterization of a metagenomic‐derived β‐lactamase from an Alaskan soil sample, named LRA‐12, and analyzed the genetic background for searching putative mobilization signals. Methods: LRA‐12‐producing Escherichia coli clone was isolated in β‐lactam‐containing agar plates from a previously constructed metagenomic library from an Alaskan soil sample. Sequence analysis of the whole insert containing the β‐lactamase gene was performed. The encoding gene was cloned in a pET28 expression vector, and LRA‐12 was purified to homogeneity. Steady‐state kinetic parameters were determined for β‐lactam antibiotics and β‐lactamase inhibitors. Conclusions: LRA‐12 has 61% amino acid identity with FEZ‐1 (a metallo‐β‐lactamase from Fluoribacter gormanii) possessing all the expected conserved motifs for class B β‐lactamases. The enzyme is able to efficiently hydrolyze all β‐lactams except monobactams, with high catalytic efficiencies towards carbapenems, cephalosporins (including oxyiminocephalosporins) and penicillins, in good agreement with the behavior of other metallo‐β‐ lactamases. These results support the hypothesis of the environmental origin of many β‐lactamases, many of them already existing in the chromosome of bacterial species with native widerange activity spectrum towards most β‐lactams, even before their recruitment and dissemination.