	As the PSM classes are closely related there are many conserved aspects. However each PSM class plays a different role, as such there are some distinctive features for each. Generally PSMs are encoded on the core genome of "staphylococcal" species however some, such as PSM-mec, are encoded on mobile genetic elements. PSMs are generally separated into one of two classes α-type PSMs and β-type PSMs, which are based upon characteristics of the two most well studied PSMs PSMα and PSMβ.