Production, isolation and purification of bacteriocins expressed by two strains of Neisseria meningitidis

The systemic Neisseria meningitidis strain P241 and the healthy pharyngeal carrier strain BT878 produce bacteriocin-like substances during growth. A method has been devised for obtaining the active substances in solution. The activity was recovered by freeze-thaw extraction of dialyzed Todd-Hewitt agar medium into which the bacteriocins had diffused during growth of the producer strains. The bacteriocins were purified more than 50-fold by ammonium-sulphate precipitation and hydrophobic interaction chromatography. They are quite stable to heat and remain active 100% after 30 min at 100 degrees C. However, the protein nature of the bacteriocins has been confirmed by their sensitivity to alpha-chymotrypsin. Gel filtration indicated an M-r of 100-110 kDa, whereas SDS-polyacrylamide gel electrophoresis produced a common band by Coomassie staining corresponding to an M-r of 47-48 kDa, suggesting a dimer form of the active protein component.