Streptococcin A-FF22: nisin-like antibiotic substance produced by a group A streptococcus

Abstract

Streptococcin A-FF22 (SA) was shown to occur as both a cell-associated (SA-CA) and an extracellular (SA-EX) component of cultures of the producer bacterium, group A streptococcus strain FF22. SA-CA was solubilized by chemical, enzymatic, and mechanical procedures, similar to those used to release M protein. The independence of SA and M protein in strain FF22 was established by chromatographic separation of the two proteins on the basis of molecular weight and isoelectric point differences between the two substances. Media supporting optimal growth of strain FF22 did not necessarily favor SA production. SA was not produced either at elevated temperatures (39 degrees C) or if the culture was maintained at pH 7 or higher. The release of SA from producer cells was enhanced at lower culture pH values. Much of the SA-CA activity seemed associated with the cell walls of the producer strain, and the nature of the binding appeared to be largely nonspecific in nature and attributable to electrostatic interaction.