Production, purification, and properties of a bacteriocin from Staphylococcus aureus isolated from saliva

Staphylococci from samples of human saliva were isolated on staphylococcal-selective agar plates. These strains were tested for the inhibition of the growth of Staphylococcus aureus FDA209P. The frequency of inhibitory strains among all of the staphylococcal isolates was 5.2%. Strain IYS2, which formed the biggest inhibitory zone against the growth of the indicator strain, was used as the producer of bacteriocin. IYS2 was identified to be S. aureus, based on its biological properties. The bacteriocin was purified by sequential procedures, including ammonium sulfate precipitation, fractionation with ethanol, ion-exchange chromatography, and gel filtration. Its molecular weight was determined to be 5,000. The isoelectric point was 10.0. In amino acid composition, lysine, histidine, aspartic acid, valine, and phenylalanine were predominant. The bacteriocin was heat stable but inactivated by proteases or peptidase. The bacteriocin had a bactericidal effect on susceptible cells. An analysis of the inhibitory spectrum among typical oral indigenous bacteria showed that Streptococcus salivarius, Propionibacterium acnes, Corynebacterium parvulum, and Actinomyces israelii were susceptible to the bacteriocin. Streptococcus mutans, Streptococcus sanguis, Streptococcus mitis, Actinomyces viscosus, Actinomyces naeslundii, Fusobacterium nucleatum, Bacterionema matruchotii, and Bacteroides melaninogenicus were resistant. The majority of S. aureus tested were susceptible, and all Staphylococcus epidermidis strains tested were resistant.