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 cultu res to subinhibitory amounts of copper sulfate. All nine strains posse ssed large plasmids, but transformation and curing results suggest tha t Cu-r is conferred by chromosomal genes. Plasmid-less Pseudomonas aer uginosa PAO-derived strains showed the same level of Cu-r as environme ntal 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-s tringency conditions but failed to hybridize at high-stringency condit ions.