Purification and properties of a cell-bound bacteriocin from a Bacteroides fragilis strain.

A cell-bound bacteriocin was extracted from a Bacteroides fragilis BF-11 strain by treating the cells with a low-molarity buffer (0.01 M Tris-hydrochloride, pH 8.0). Sucrose osmotic shock experiments and ultrasonic lysis of whole cells indicated that the majority of the bacteriocin was located at the cell surface. Culture supernatants contained no significant bacteriocin activity. The bacteriocin was purified by DEAE-cellulose and Sephacryl S200 chromatography and had an apparent molecular weight of approximately 7,000. It was relatively heat stable and was inactivated by proteases. There was a delay of approximately 3.5 h before DNA, RNA, and protein synthesis were inhibited by the bacteriocin. Inhibition of macromolecular synthesis coincided with lysis of the susceptible indicator strain.