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BIO 303
Mycobacterium
Smegmatis
Number: 14
Jourdan Beasley
9/25/2011
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Tests Used:

Gram Stain: nothing showed up

Acid-Fast Stain: (+)
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In Microbiology, scientist use different test to determine what bacterium they are
studying. For class we as a class were given an unknown vial of bacteria and had to perform
certain test to identify what we each had. I started that day with gram stain and it came back
negative for any bacterium. After some research I found that a gram stain should come back
positive and after trying a gram stain multiple times nothing ever showed up. I then decided
to try an acid-fast stain. My slide was positive for an acid fast. After more research I found
that with a positive acid fast stain out of the seven bacteria we could have possibly had that
my test tube contained Mycobacterium Smegmatis.
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Mycobacterium Smegmatis was first discovered and isolated in 1884. Mycobacteria are
rod-shaped and some species of Mycobacteria can cause tuberculosis and leprosy. The bacteria
Mycobacterium Smegmatis is classified as a syphrophytic species. Since Mycobacterium
Smegmatis is syphrophytic it has very little threat to living organisms and does not cause
infections. It is considered to be non-pathogenic but is only dangerous in extreme cases. There
have been cases where Mycobacterium Smegmatis was dangerous, but there has not been a
recorded incident in over 15 years.
A Syphrophytic species can be defined as a bacterium that grows on or gets its
nourishment from dead or decaying organic matter. Mycobacterium Smegmatis is an obligate
aerobic organism. Being an obligate aerobic organism, Mycobacterium Smegmatis requires
oxygen to survive. This bacterium can be found in soil, water or plants and can also usually be
found near large bodies of water. This bacterium can be different colors depending on where it is
found and how long it has had time to grow. For example, if Mycobacterium Smegmatis is
growing on accessible nutrients then it will be a creamy white color. If it has been abundantly
growing for about 48 hours or more then it turns from creamy white to yellow. Mycobacterium
Smegmatis will also be waxy because it does have a very unique gram positive cell wall that is
coated with mycolic acid. Mycobacterium Smegmatis’s cell wall is a gram positive cell wall but
because of the mycolic acid, it is very difficult to stain this bacterium with a gram stain. Since
the mycolic acid creates a waxy cell wall, it prevents the crystal violet from getting into the cell
wall; therefore, Mycobacterium usually does not show up at all on a Gram Stain.
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Works Cited
Nester, Eugene W., and Denise G. Anderson. Microbiology: a Human Perspective.
Boston, MA: McGraw-Hill, 2005. Print.
Gordon, R., Smith, M. "RAPIDLY GROWING, ACID FAST BACTERIA I. Species' Descriptions
of Mycobacterium phlei Lehmann and Neumann and Mycobacterium smegmatis (Trevisan)
Lehmann and Neumann". Journal of Bacteriology. 1953. Volume 66. p. 4148. http://www.pubmedcentral.nih.gov/pagerender.fcgi?artid=357089&pageindex=1