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Appl. Environ. Microbiol., 08 1995, 2891-2897, Vol 61, No. 8
GW Sundin and CL Bender
Expression of the strA-strB streptomycin resistance (SMr) genes was
examined in Pseudomonas syringae pv. syringae and Xanthomonas campestris
pv. vesicatoria. The strA-strB genes in P. syringae and X. campestris were
encoded on elements closely related to Tn5393 from Erwinia amylovora and
designated Tn5393a and Tn5393b, respectively. The putative recombination
site (res) and resolvase-repressor (tnpR) genes of Tn5393 from E.
amylovora, P syringae, and X. campestris were identical; however, IS6100
mapped within tnpR in X. campestris, and IS1133 was previously located
downstream of tnpR in E. amylovora (C.-S Chiou and A. L. Jones, J.
Bacteriol. 175:732-740, 1993). Transcriptional fusions (strA-strB::uidA)
indicated that a strong promoter sequence was located within res in
Tn5393a. Expression from this promoter sequence was reduced when the tnpR
gene was present in cis position relative to the promoter. In X. campestris
pv. vesicatoria, analysis of promoter activity with transcriptional fusions
indicated that IS6100 increased the expression of strA-strB. Analysis of
codon usage patterns and percent G+C in the third codon position indicated
that IS6100 could have originated in a gram-negative bacterium. The data
obtained in the present study help explain differences observed in the
levels of SMr expressed by three genera which share common genes for
resistance. Furthermore, the widespread dissemination of Tn5393 and
derivatives in phytopathogenic prokaryotes confirms the importance of these
bacteria as reservoirs of antibiotic resistance in the environment.
Copyright © 1995, American Society for Microbiology
Expression of the strA-strB streptomycin resistance genes in Pseudomonas syringae and Xanthomonas campestris and characterization of IS6100 in X. campestris
Department of Plant Pathology, Oklahoma State University, Stillwater 74078, USA.
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