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Updated: Aug 19, 2026

Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins
Published on: September 30, 2014
Production, isolation and purification of bacteriocins expressed by two strains of Neisseria meningitidis
J Allunans1, M Bjørås, E Seeberg
1Kaptein W. Wilhelmsen og Frues Institute of Medical Microbiology, University of Oslo, Rikshospitalet, Norway.
Abstract:
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 Mr of 100-110 kDa, whereas SDS-polyacrylamide gel electrophoresis produced a common band by Coomassie staining corresponding to an Mr of 47-48 kDa, suggesting a dimer form of the active protein component.
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