Relationship of free ionic copper and toxicity to bacteria in solutions of organic compounds

The complexation of cupric ions added to solutions of different organic compounds and to culture media was determined using an ion-specific electrode to ascertain the toxic forms of copper. Toxicity of Cu 2+ to copper-sensitive and copper-tolerant strains of Pseudomonas syringae was reduced in the presence of all organic compounds tested, including 100 mM solutions of glucose, fructose, sucrose, succinate, and particularly citrate. The apparent toxicity of copper solutions was reduced 30× or more in the presence of organic solute (...)