Extracellular product(s) of Staphylococcus aureus stimulate their own growth

The effect of extracellular products obtained from culture supernatant of Staphylococcus aureus strain Cowan I on the bacterial growth was studied in a synthetic medium. Addition of the extracellular products to a fresh medium stimulated growth already after 2 h of incubation, with an approximately two-fold increase in cell density as compared to an unsupplemented medium, probably by promoting an initiation of growth accompanied by a reduction of the initial lag phase. The growth-stimulating effect was also monitored as an increase of adenosine triphosphate (ATP) in the bacterial culture during the different phases of growth.