Constitutive expression of a chromosomal class A (BJM group 2) beta-lactamase in Xanthomonas campestris.
Sequencing of the upstream region of the beta-lactamase gene from Xanthomonas campestris pv. campestris 11 (bla(XCC-1)) revealed the cognate ampR1 gene (289 amino acids, 31 kDa). It runs divergently from bla(XCC-1) with a 100-bp intergenic region (IG) containing partially overlapped promoters with structural features typical of the bla-ampR IG. The deduced AmpR1 protein shows significant identity in amino acid sequence and conserved motifs with AmpR proteins of other species, e.g., of Pseudomonas aeruginosa (58.2% amino acid identity). Results of insertional mutation, complementation tests, and beta-lactamase assays suggested that expression of bla(XCC-1) was constitutive and dependent on AmpR1. Four bla genes and two ampR genes are present in the fully sequenced X. campestris pv. campestris ATCC 33913 genome, with XCC3039 and XCC3040 considered the analogues of bla(XCC-1) and ampR1, respectively. An ampR1 homologue was detected by Southern hybridization in the ampicillin-resistant Xanthomonas strains, which appear to express beta-lactamase constitutively. Although the significance remains to be studied, constitutive expression of beta-lactamase by a widespread bacterial genus raises environmental concerns regarding the dissemination of resistance genes.
Weng
Shu-Fen
SF
Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan, Republic of China.
Lin
Juey-Wen
JW
Chen
Chih-Hung
CH
Chen
Yih-Yuan
YY
Tseng
Yi-Hsuan
YH
Tseng
Yi-Hsiung
YH
D000668:Ampicillin Resistance / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics*; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D008156:Luciferases / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D014974:Xanthomonas / Q000201:enzymology* / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; C071526:AmpR protein, Bacteria; D008156:Luciferases