M. luteus can be found in many places such as the human skin, water, dust, and soil. Micrococcus is generally thought of as harmless bacterium, but there have been rare cases of Micrococcus infections in people with compromised immune systems, as occurs with HIV patients.
Therefore when used in gel electrophoresis, markers effectively provide a logarithmic scale by which to estimate the size of the other fragments (providing the fragment sizes of the marker are known). Protein, DNA, and RNA markers with pre-determined fragment sizes and concentrations are commercially available.
Tracking Dyes (Molecular Biology) In gel electrophoresis using discontinuous buffer systems, disc electrophoresis, dyes migrating with a net mobility intermediate between that of the leading and trailing ions of a moving boundary are used to mark the moving boundary (tracking dyes).