Characterization of the mesB gene and expression of bacteriocins by Leuconostoc mesenteroides Y105

Leuconostoc mesenteroides Y105, previously described for production of mese ntericin Y105, an anti-listeria bacteriocin, was shown to secrete a second bacteriocin. The latter was purified, and its molecular mass of 3446 Da, ob tained by mass spectrometric analysis, indicates that this bacteriocin shou ld be identical to mesenterocin 52B [Revol-Junelles et al;, Lett Appl Micro biol 23:120, 1996]. This second bacteriocin produced by L. mesenteroides Y1 05 was named mesentericin B105. Its structural gene, mesB, was then localiz ed by a reverse genetic approach, cloned. and sequenced. MesB was found on the pHY30 plasmid, next to mesY gene clusters. Curing experiments led to is olation of two L. mesenteroides Y105 derivatives, named L. mesenteroides Y2 9 and Y30. The latter had lost pHY30 plasmid, encoding bacteriocin determin ants, therefore explaining its phenotype (MesY-, MesB-). On the contrary, Y 29 derivative still harbors the pHY30 but did not produce any bacteriocin. Thus, its phenotype could Likely result from a point mutation within a gene , probably encoding a protein involved in production of both mesentericin Y 105 and mesentericin B105.