Deoxyribonucleic Acid Base Composition and Taxonomy of Thiobacilli and some Nitrifying Bacteria

SUMMARY: The DNA base composition of 14 authentic strains of the genus Thiobacillus, determined by caesium chloride density gradient centrifugation, was found to vary from 51 to 68 mole % guanine+cytosine (G + C). The mole % G + C values for the various species are as follows: T. thiooxidans and T. concretivorus 51-52, T. neopolitanus and T. ferrooxidans 56-57, and T. thioparus, T. thiocyanoxidans, T. denitrificans, T. novellus and T. trautweinii 62-68. Another group of chemoautotrophic bacteria, the nitrifiers Nitrosomonas europaea and Nitrobacter agilis, were found to have a G + C content of 52 and 65%, respectively. The results are compared with other types of taxonomic studies made with these and related bacteria.