title: Cadmium and zinc sensitivity and tolerance in Klebsiella (Aerobacter) aerogenes.
abstract: The resistance of strains of K. aerogenes NCIB 418 'trained' to Cd2+ or Zn2+ in liquid medium is graded to the training concentration. Training to Cd2+ increased the sensitivity to Zn2+ but training to Zn2+ reduced the sensitivity to Cd2+. The trained organisms, particularly those trained to Cd2+, grow slowly in medium containing the metals and the growth rates after 20 and 200 subcultures were not significantly different. The survival of untrained organisms on Cd2+-agar decreased progressively as the Cd2+ concentration was increased, but a threshold concentration of Zn2+ was necessary before any decrease set in. Very low concentrations of Zn2+ potentiated the lethal action of Cd2+ and vice versa, whereas chelating the metal ions with citrate, aspartate or gluconate eliminated it. Nutrient-limitation, as might occur in natural environments, also had a profound effect. Mg2+-limited organisms were particularly resistant to both metals whereas glucose-, NH+4 and PO3-4-limited organisms were very sensitive to Cd2+, and glucose- and K+-limited organisms to Zn2+.
mesh_terms: D000222:Adaptation, Physiological; D002104:Cadmium / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D004357:Drug Synergism; D005947:Glucose / Q000378:metabolism; D005994:Glycerophosphates / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
chemical_list: D002614:Chelating Agents; D005994:Glycerophosphates; D002104:Cadmium; D008274:Magnesium; D005947:Glucose; D015032:Zinc; D011188:Potassium