Several acidophilic chemolithoautotrophic and heterotrophic strains were isolated from acid mine drainage samples from Garubathan, West Bengal, India. The strains, chemolithoautotrophic DK6.1 and heterotrophic DKAP1.1, used in this study were assigned to the species Acidithiobacillus ferrooxidans and Acidiphilium cryptum, respectively. Unamended filtered and subsequently autoclaved elemental sulfur spent medium of A. ferrooxidans was used as the medium to study heterotrophic growth of A. cryptum DKAP1.1. While characterizing the heterotrophic strain, an inhibitory effect of thiosulfate on A. cryptum DKAP1.1 was identified. The lethality of thiosulfate broth was directly related to the concentration of thiosulfate in the medium. Nonviability of A. cryptum DKAP1.1 in the presence of thiosulfate was alleviated by A. ferrooxidans DK6.1 in co-culture. Microbiological data on a positive growth effect for A. ferrooxidans DK6.1 caused by co-culturing in solid media in the presence of A. cryptum DKAP1.1 is also presented.