CHROMOSOME-ENCODED INDUCIBLE COPPER RESISTANCE IN PSEUDOMONAS STRAINS

Nine Pseudomonas strains were selected by their high copper tolerance from a population of bacteria isolated from heavy-metal polluted zones. Copper resistance (Cu-r) was inducible by previous exposure of cultures to subinhibitory amounts of copper sulfate. All nine strains possessed large plasmids, but transformation and curing results suggest that Cu-r is conferred by chromosomal genes. Plasmid-less Pseudomonas aeruginosa PAO-derived strains showed the same level of Cu-r as environmental isolates and their resistance to copper was also inducible. Total DNA from the environmental Pseudomonas, as well as from P. aeruginosa PAO strains, showed homology to a Cu-r P. syringae cop probe at low-stringency conditions but failed to hybridize at high-stringency conditions.