Plasmid-mediated copper resistance in Xanthomonas euvesicatoria pv. perforans: determination of plasmid copy number and stability.

Plasmid-borne copB in Xanthomonas euvesicatoria pv. perforans increases copB gene copy number and expression, but plasmids can partially or completely be lost without copper selection.

• Why it matters: Copper resistance is widespread and challenges bacterial spot management, yet how plasmid versus chromosomal localization affects resistance gene dosage, expression, and stability is unclear.
• What they did: The study compared strains with chromosomal-only versus plasmid-encoded versus both cop operons, measuring copB copy number and expression and assessing plasmid stability during in vitro growth without copper.
• The result: Relative to chromosomal-only strains, plasmid-encoded resistance increased copB copy number, and strains with both locations showed an even greater increase; copB expression rose in both groups, while copper-free growth led to partial/complete plasmid loss and transposase-mediated plasmid rearrangements.