1981 Volume 47 Issue 4 Pages 480-487
An antibacterial substance released from cells of Xanthomonas campestris pv. citri Ku 7508 by chloroform treatment was purified and its several properties were examined. The substance was not precipitated by centrifuging even at 60, 000×g for 60min, partially precipitated at 75% acetone (final concentration) and completely precipitated at 60% saturation with ammonium sulfate. It was not dialysed through Visking tube and inactivated by heating at 60 C for 30min. The purification of this substance was conducted by DEAE ion-exchange cellulose column followed by Ultrogel column. Antibacterial activity of eluates was corresponded with the peak of UV absorbance at 280nm. A typical UV spectrum of protein, i.e., maximum at 280nm and minimum at 250 nm was observed. Two or three bands were detected by Coomassie-blue staining at disc gel electrophoresis of this active fraction. One of the band having antibacterial activity was sliced and repeatedly subjected to disc gel electrophoresis and single band was isolated. Molecular weight of this substance estimated by SDS-polyacrylamide gel electrophoresis was about 300, 000 daltons. Antibacterial substance caused retardation of bacterial growth due to aggregation or disruption of cells during the first several hr. The effet, however, disappeared within 24hr of incubation. Electron microscopic observation revealed that the antibacterial substance caused leaking of bacterial cytoplasm due to disruption of cell wall. These results suggest that the antibacterial substance was a kind of bacteriocin.