Genetic characterisation and heterologous expression of leucocin C, a class IIa bacteriocin from Leuconostoc carnosum 4010.
Leuconostoc carnosum 4010 is a protective culture for meat products. It kills the foodborne pathogen Listeria monocytogenes by producing two class IIa (pediocin-like) bacteriocins, leucocin A and leucocin C. The genes for leucocin A production have previously been characterised from Leuconostoc gelidum UAL 187, whereas no genetic studies about leucocin C has been published. Here, we characterised the genes for the production of leucocins A and C in L. carnosum 4010. In this strain, leucocin A and leucocin C operons were localised in different plasmids. Unlike in L. gelidum, leucocin A operon in L. carnosum 4010 only contained the structural and the immunity genes lcaAB without transporter genes lcaECD. On the contrary, leucocin C cluster included two intact operons. Novel genes lecCI encode the leucocin C precursor and the 97-aa immunity protein LecI, respectively. LecI shares 48 % homology with the immunity proteins of sakacin P and listeriocin. Another leucocin C operon lecXTS, encoding an ABC transporter and an accessory protein, was 97 % identical with the leucocin A transporter operon lcaECD of L. gelidum. For heterologous expression of leucocin C in Lactococcus lactis, the mature part of the lecC gene was fused with the signal sequence of usp45 in the secretion vector pLEB690. L. lactis secreted leucocin C efficiently, as shown by large halos on lawns of L. monocytogenes and Leuconostoc mesenteroides indicators. The function of LecI was then demonstrated by expressing the gene lecI in L. monocytogenes. LecI-producing Listeria was less sensitive to leucocin C than the vector strain, thus corroborating the immunity function of LecI.
Department of Food and Environmental Sciences, University of Helsinki, P.O. Box 56, Helsinki, Finland.
Xing
X
Wan
Ruiqing
R
Li
Per E J
PE
Saris
Timo M
TM
Takala
D001430:Bacteriocins / Q000096:biosynthesis* / Q000235:genetics*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D015870:Gene Expression; D013294:Lactococcus lactis / Q000235:genetics / Q000378:metabolism; D007934:Leuconostoc / Q000235:genetics*; D008089:Listeria monocytogenes / Q000187:drug effects; D053858:Metabolic Networks and Pathways / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D005810:Multigene Family; D009876:Operon; D010957:Plasmids; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D001430:Bacteriocins; D004269:DNA, Bacterial