Figure 1 is a culture of Mycobacterium phlei growing in a slant of Lowenstein-Jensen agar.  Two- to four-day-old cultures of this organism are good examples of a rapidly growing pigmented Mycobacterium sp. The colonies have a classic bread-crumb appearance.

Figure 2 is an acid-fast stain of M. phlei pure culture taken from a Lowenstein-Jensen agar slant.  Two- to 3-day-old cultures make good specimens for acid-fast staining. This image was obtained with a bright-field microscope at a magnification of ´1,000.  This image would help students visualize the morphology and color reaction of a mycobacterial species following acid-fast staining.

M. phlei can sometimes be found on grass and hay.  It has not thus far been shown to cause infection in humans, grows quite rapidly (1 to 2 days at 37^oC), and would make a good specimen for use in identification of a mycobacterial unknown.