Mycobacterium heckeshornense is a species of the phylum Actinobacteria (Gram-positive bacteria with high guanine and cytosine content, one of the dominant phyla of all bacteria), belonging to the genus Mycobacterium. Gram-positive, nonmotile and acid-fast rods. Cells are typically rod-shaped, with some coccoid forms. Colony characteristicsSmooth, yellow scotochromogenic colonies appear after 4 weeks of culture. Physiology Differential characteristics