Thiobacillus acidophilus: a study of its presence in Thiobacillus ferrooxidans cultures.

A study has been undertaken to account for the presence of Thiobacillus acidophilus in iron-grown cultures of Thiobacillus ferrooxidans. Attempts to adapt T. acidophilus to ferrous iron were not successful but the facultative autotroph grew to a limited extent in the spent medium of T. ferrooxidans and was able to grow oligotrophically. Possible oligotrophic substrates were methanol, ethanol, and sulphide. Thiobacillus ferrooxidans may benefit from the presence of T. acidophilus because in mixed cultures some inhibiting organic compounds such as alcohols, organic acids, and amino acids were utilized by T. acidophilus. The number of T. acidophilus cells in heterogeneous cultures with T. ferrooxidans was of the same order of magnitude as the number of T. ferrooxidans cells as revealed by fluorescent-labelled antibodies.