DEOXYRIBONUCLEIC ACID HOMOLOGIES AMONG SPECIES OF THE GENUS THIOBACILLUS

Abstract

The DNA-DNA homologies were determined among 14 strains of 13 species in the genus Thiobacillus. DNA from Thiobacillus versutus (synonym "Thiobacillus rapidicrescens") THI 041 and THI 024 did not react with DNAs from other species of facultatively chemolithotrophic Thiobacillus. This supports our previous conclusion, based on chemotaxonomic and physiological characteristics, that "T. rapidicrescens" is a new species. Both strains of Thiobacillus sp. THI 011 and Thiobacillus sp. THI 051, which were isolated from an activated sludge enriched with thiocyanate, were considered to be new species. Thiobacillus acidophilus THI 061 was closely related to "Thiobacillus organoparus" THI 071 in their DNA-DNA homology, and THI 071 was considered to be a strain of T. acidophilus. "Thiobacillus delicatus" THI 091, Thiobacillus perometabolis THI 023, and Thiobacillus intermedius THI 101 were regarded as three distinct species on the basis of DNA-DNA homology and phenotypic characteristics. Homologies were low among "Thiobacillus denitrificans" THI 151, Thiobacillus thioparus THI 111, Thiobacillus neapolitanus THI 121, and Thiobacillus ferrooxidans THI 135. Therefore, these organisms were considered to be separate species. The DNA-DNA homologies supported the classification of the species in the genus Thiobacillus on the basis of the ubiquinone system in the respiratory chain, composition of cellular fatty acids, DNA base composition, and nutritional characteristics.