Genomic and physiological diversity amongst strains of Thiobacillus ferrooxidans,and genomic comparison with Thiobacillus thiooxidans

Twenty-three strains of Thiobacillus ferrooxidans of known pedigree were examined. Thirteen strains survived 65° C for 5 min and 7 of these for 10 min, but sporulation was never observed. All strains grew between 25° C and 35° C and some strains grew at 5° and 40° C. They were genomically diverse, comprising 7 DNA homology groups, and the GC content varied from 55–65 mol %. Correlation between genomic group and growth temperature was noted. All strains grew on ferrous sulfate as energy source, but some failed to utilize elemental sulfur. Acidified thiosulfate supported growth of most of the strains examined but it was judged to be a poor substrate upon which to base taxonomic conclusions because of decomposition of thiosulfate in acid. Six strains of Thiobacillus thiooxidans showed negligible genomic affinity to T. ferrooxidans, and they comprised 2 DNA homology groups and their GC content varied from 52–62 mol%. Anomalies due to contaminants in cultures of T. ferrooxidans were resolved, and the contaminants were identified.