phenol-soluble modulins (psms) are a family of small protein, that carry out a variety of functions, including acting as toxins, assisting in biofilm formation, and colony spreading. psms are produced by "staphylococcus" bacteria including methicillin-resistant "staphylococcus aureus" (mrsa)"," and "staphylococcus epidermidis." many psms are encoded within the core genome and can play an important virulence factor. psms were first discovered in "s. epidermidis" by seymour klebanoff and via hot-phenol extraction and were described as a pro-inflammatory complex of three peptides. since their initial discovery, numerous roles of psms have been identified. however, due in part to the small size of many psms, they have largely gone unnoticed until recent years.