This paper deals with a preliminary study of the nucleic acid fraction of ten representative strains of atypical acid-fast bacilli isolated from sputum and gastric contents of patients with proven or suspected tuberculosis (Loesch and Petrik, 1939). Strains Ya and Fe were isolated from cultures which also contained colonies of virulent human-type tubercle bacilli. Cultures from which the remaining eight strains were obtained showed one to four colonies of the atypical acid-fast bacilli. The two

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... principal groups of nucleic acids are desoxyribonucleic acid, the so-called animal type, yielding after hydrolysis the pyrimidine bases cytosine and thymine, the purine bases adenine and guanine, the sugar d-2-desoxyribose and phosphoric acid; and ribonucleic acid, the so-called plant type, which differs with regard to one pyrimidine base, yielding uracil instead of thymine, and the sugar d-ribose. It was generally believed that the former was to be found exclusively in animal tissues and the latter in plant tissues. However, evidence is accumulating (Allen, 1941) to support the view that desoxyribonucleic acids may be found in all nuclei regardless of origin, and, ribonucleic acid mainly in the cytoplasm. The investigations of Johnson and Brown (1922,. 1923) and Brown and Johnson (1923) of the nucleic acid of tubercle bacilli have shown it to be of animal type. On the other hand Coghill (1931) found the nucleic acid of the timothy bacillus to be of plant type. In view of this difference in the nucleic acid content of these microorganisms it was felt that a study of the nucleic acid of the atypical acid-fast bacilli might be of value in correlating these microorganisms with tubercle bacilli and thus aid in evaluating the significance of their presence in sputum and other excreta. MATERIALS AND METHODS The acid-fast strains used in this study were three chromogens: Cl, orange; Ya, buff; and Fe, yellow. The others were white to cream colored Me, Ge, Ke, Sn, Rh, Wo and P1. The original colonies were approximately hemispherical, smooth, glistening, easily suspended in physiological salt solution, acid-fast with Ziehl-Neelsen stain and were avirulent for guinea pigs. Similar acid-fast bacilli have been described by many workers; among the most recent are Thomson (1932) , Pinner (1935) , Baldwin (1942) and Medlar et al. (1943). Avian, Rl, and H37 tubercle bacilli and a yeast were included as controls. Preparation of Nucleic Acid The microorganisms were grown on a Long's synthetic medium (asparagin 4.0 g, sodium citrate 6.0 g, secondary potassium phosphate (K2HPO4) 0.5 g, 347 on May 9, 2020 by guest