Identification of a Novel β-Lactamase Produced by Xanthomonas campestris, a Phytopathogenic Bacterium

The Xanthomonas campestris pv. campestris 11 chromosome encodes a periplasmic β-lactamase of 30 kDa. Gene replacement and complementation confirmed the presence of this enzyme. Its deduced amino acid sequence shows identity and conserved domains between it and Stenotrophomonas maltophilia L2 and other Ambler class A/Bush group 2 β-lactamases. Southern hybridization detected a single homologous fragment in each of 12 other Xanthomonas strains, indicating that the presence of a β-lactamase gene is common among xanthomonads.