Cellular Morphology of Form 2 Mycobacteria in Slide Culture

Abstract

SUMMARY: Form 2 of a strain of Mycobacterium tuberculosis var. hominis was isolated. The cellular morphology of this organism when growing in glycerol agar slide culture is described. The form 2 strain grew by the initial production of septate filaments which soon ramified as a result of pseudobranching. The filaments fragmented early into bacillary elements and much later into coccoid elements. Endospores were formed within some of the bacillary elements. The young cells were Gram negative and the older cells Gram positive. The cells were never acid-fast. Growth occurred in aerobic and anaerobic culture, but the morphological changes progressed more rapidly under anaerobic conditions. The strain has many characteristics also found in some members of the Actinomycetaceae; however there are also differences, the most important of which is endospore formation. Thus the strain cannot yet be classified.