Mmushi T MSc (Microbiology).pdf

1.7.3. Mycobacterium smegmatis and Rhodococcus erythropolis
Mycobacterium smegmatis is 3.0 to 5.0 µm long bacilli, aerobic and nonmotile
bacterium. Mycobacterium smegmatis is an acid-fast bacterial species and is generally
considered a non-pathogenic microorganism. However, in some very rare cases it may
cause disease in an immunocompromised animal. Its major component of the cell wall
is made up of long fatty acid chain (mycolic acids) with functional groups attached to it.
The percentage of carbon atoms differs from species to species and the presence of
mycolic acids gives Mycobacterium tuberculosis many characteristics that resist medical
treatment (Steck et al., 1978). Mycolic acids contribute to the organism’s increased
resistance to chemical damage and dehydration, and prevent the effective activity of
hydrophobic antibiotics. In addition mycolic acids are important for survival and
pathogenesis by allowing the bacterium to grow readily inside macrophages and
effectively hiding from the host's immune system hence it is difficult to treat because of
its asymptotic characteristics (Bhatt et al., 2007).
Mycobacterium smegmatis is commonly used in research analysis of other
mycobacterium species in laboratory experiments due to its fast growing capability and
being non-pathogenic (McGaw et al., 2008). Figure 1.20 shows typical cells of
Mycobacterium smegmatis stained with the acid fast stain method.
Fig.1.20. Mycobacterium smegmatis (Reynolds et al., 2009).
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