METAL RESISTANCE IN ACIDOCELLA STRAINS AND PLASMID-MEDIATED TRANSFER OF THIS CHARACTERISTIC TO ACIDIPHILIUM-MULTIVORUM AND ESCHERICHIA-COLI

Acidophilic heterotrophic strain GS19h of the genus Acidocella exhibit ed extremely high resistance to CdSO4, and ZnSO4,, with a MIC of 1 M f or each, The respective MICs for an Acidocella aminolytica strain were 400 and 600 mM, The MICs of NiSO4, for the above strains were 200 and 175 mM, respectively, These strains were also resistant to CuSO4,, th e MICs being 20 and 40 mM, respectively, An Acidocella facilis strain showed resistance only to ZnSO4 with a MIC of 150 mM, The metal salts, in general, extended the lag period, log period, and generation time, with decreases in growth rate and optimum growth, A. aminolytica and strain GS19h each contain more than one plasmid, while A, facilis cont ains none, After transformation by electroporation with the plasmid pr eparation from strain GS19h, an Acidiphilium multivorum strain became highly resistant to cadmium and zinc, and the plasmid profile of the t ransformed cells was found to differ from that of the original Acidiph ilium multivorum strain, Escherichia coli HB101 and DH5 alpha also exh ibited more resistance to these metals, especially zinc, after transfo rmation with the total plasmid preparation of strain GS19h or a 24.0-M Da plasmid of the same strain, although no plasmid was detected in the transformed cells, Thus, the results derived mainly through genetic e xperiments demonstrate for the first time the plasmid-mediated transfe r of metal resistance for an acidophilic bacterium.