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Antimicrobial Agents and Chemotherapy, January 2004, p. 209-215, Vol. 48, No. 1
0066-4804/04/$08.00+0     DOI: 10.1128/AAC.48.1.209-215.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Constitutive Expression of a Chromosomal Class A (BJM Group 2) ß-Lactamase in Xanthomonas campestris

Shu-Fen Weng,1 Juey-Wen Lin,2 Chih-Hung Chen,1 Yih-Yuan Chen,1 Yi-Hsuan Tseng,1 and Yi-Hsiung Tseng1*

Institute of Molecular Biology,1 Institute of Biochemistry, National Chung Hsing University, Taichung 402, Taiwan, Republic of China2

Received 28 February 2003/ Returned for modification 29 April 2003/ Accepted 23 September 2003

Sequencing of the upstream region of the ß-lactamase gene from Xanthomonas campestris pv. campestris 11 (blaXCC-1) revealed the cognate ampR1 gene (289 amino acids, 31 kDa). It runs divergently from blaXCC-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 ß-lactamase assays suggested that expression of blaXCC-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 blaXCC-1 and ampR1, respectively. An ampR1 homologue was detected by Southern hybridization in the ampicillin-resistant Xanthomonas strains, which appear to express ß-lactamase constitutively. Although the significance remains to be studied, constitutive expression of ß-lactamase by a widespread bacterial genus raises environmental concerns regarding the dissemination of resistance genes.

* Corresponding author. Mailing address: Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan, Republic of China. Phone: 886-4-2285-1885. Fax: 886-4-2287-4879. E-mail: yhtseng{at}dragon.nchu.edu.tw.

Antimicrobial Agents and Chemotherapy, January 2004, p. 209-215, Vol. 48, No. 1
0066-4804/04/$08.00+0     DOI: 10.1128/AAC.48.1.209-215.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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