Two types of slowly growing, nonphotochromogenic mycobacteria obtained from soil by the mouse passage method: Mycobacterium terrae and Mycobacterium novum.

Two types of slowly growing, nonphotochromogenic mycobacteria, Mycobacterium terrae and Mycobacterium novum, were isolated from soil by mouse body passage method. The former was presented previously by the present author as a new species. Its characteristics are better clarified in this paper based on the data of 93 strains. Mycobacterium novum is a slowly growing nonphotochromogen. It grows at 10 to 14 days on egg media and does not grow on Sauton agar. It grows on Ogawa egg medium containing either 0.2% (w/v) sodium p-aminosalicylate, 0.1% (w/v) sodium salicylate or 0.25 mg/ml NH2OH·HCl. It is differentiated from M. tuberculosis, M. bovis and M. microti by these characters. It grows at 28 C and 37 C, but does not grow at 45 C. Other characteristics are: nitrate not reduced; negative two week arylsulphatase; negative niacin test; and no amidase clemonstrated. None of the carbohydrates and nitrogen compounds tested could be utilized as the sole source of carbon or of nitrogen in synthetic agar medium. It survived in mouse organs for three to four weeks. It was noticed that these mycobacteria occur very commonly in soil.