Detection of Heterotrophic Contaminants in Cultures of Thiobacillus ferrooxidans and Their Elimination by Subculturing in Media Containing Copper Sulphate

Summary: Of the four cultures of Thiobacillus ferrooxidans held by the National Collections of Industrial and Marine Bacteria, U.K., two were found to be contaminated with acidophilic heterotrophic bacteria. One of the contaminated cultures was the type strain (NC1B 8455) of T. ferrooxidans; the equivalent culture from the American Type Culture Collection (ATCC 23270) was found not to be contaminated. Heterotrophic contaminants could be subcultured along with T. ferrooxidans in media containing ferrous iron, but devoid of organic material, and remained viable in mixed cultures for periods of at least one year. Subculturing in media containing high concentrations of copper ions resulted in the elimination of the heterotrophic bacteria.