We attempted to characterize a purified bacteriocin(N-ABC)elaborated by Streptococcus mutans Rm-10. Isoelectrofocusing revealed that the pl value of this purified material was 4.5. N-ABC was stable to heating at 100℃ for 30 min, but was partially destroyed by heat treatment at 121℃ for 10 min and 20 min. (Residual activities were 50% and 12.5%, respectively). Although N-ABC could withstand exposure to pH between 2.0 and 9.0, exposure to pH 11.0 resulted in complete loss of activity. It was partially destroyed with trypsin, pepsin, papain, α-chymotrypsin, β-galactosidase, α-galactosidase and endo-β-galactosidase, suggesting that the active site of this bacteriocin may exist both in protein and carbohydrate. It was active against other mutans streptococci as well as strains of Streptococcus salivarius, Enterococcus faecalis, Porphyromonas gingivalis and Fusobacterium nucleatum, but not against strains of Peptostreptococcus indolicus, Veillonella parvula, Prevotella melaninogenica, Prevotella intermedia or Prevotella nigrescens. N-ABC killed Enterococcus faecalis ODU immediately in a dosedependent manner by a bactericidal mode of action, because N-ABC did not display bacterial lysis on sensitive cells. The antibacterial effect of N-ABC was temperature dependent, with no killing at 4℃. These results indicate that this bacteriocin is similar to two bacteriocins previously reported by Muramatsu in mode of action, although it is different from them in isoelectric point, in its sensitivity to heat and enzymes, in its stable pH range and in its antibacterial spectrum.
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