Mycobacterium smegmatis

Mycobacterium smegmatis is 3.0 to 5.0 µm long with a bacillus shape, an acid-fast bacterial species in the phylum Actinobacteria. It can be stained by Ziehl-Neelsen method and the auramine-rhodamine fluorescent method. It was first reported in 1884. Alvarez and Tavel found organisms similar to Lustgarten, who first discovered Mycobacterium. This organism was later named M. smegmatis.

It is considered a non-pathogenic microorganism although, in rare cases, it can cause disease. M. smegmatis is useful for the research analysis of other Mycobacteria species in laboratory experiments. Since it is a fast grower and non-pathogenic it makes a simple model that is easy to work with. It shares more than 2000 homologs with M. tuberculosis and shares the same unusual cell wall structure of M. tuberculosis and other mycobacterial species.

The discovery of plasmids, phages, and mobile elements has enabled the construction of dedicated gene-inactivation and gene reporter systems. The M. smegmatis strain is now the work-horse of mycobacterial genetics. It is readily available in most laboratory media and can form visible colonies in 3-5 days.