Chromosome-Encoded Broad-Spectrum Ambler Class A β-Lactamase RUB-1 from Serratia rubidaea

Whole-genome sequencing of Serratia rubidaea CIP 103234^T revealed a chromosomally located Ambler class A β-lactamase gene. The gene was cloned, and the β-lactamase, RUB-1, was characterized. RUB-1 displayed 74% and 73% amino acid sequence identity with the GIL-1 and TEM-1 penicillinases, respectively, and its substrate profile was similar to that of the latter β-lactamases. Analysis by 5' rapid amplification of cDNA ends revealed promoter sequences highly divergent from the Escherichia coli σ⁷⁰ consensus sequence. This work further illustrates the heterogeneity of β-lactamases among Serratia spp.