ABSTRACTSeveral molecular taxonomic studies have revealed that many natural (wild)Lactococcus lactisstrains of dairy origin which are phenotypically representative of theL. lactissubspecieslactiscluster genotypically within subspeciescremorisandvice versa. Recently, we isolated two wild nisin-producing (Nis+)L. lactisstrains, M78 and M104, of thelactisphenotype from Greek raw milk (J. Samelis, A. Lianou, A. Kakouri, C. Delbès, I. Rogelj, B. B. Matijašic, and M. C. Montel, J. Food Prot. 72:783–790, 2009); strain M78 possess a novel nisin A sequence (GenBank accession numberHM219853). In this study, the actual subspecies identity of M78 and M104 isolates was elucidated, using 16S rRNA andacmA(encoding lactococcalN-acetylmuramidase) gene and histidine biosynthesis operon polymorphisms and 16S rRNA andldh(encoding lactate dehydrogenase) gene phylogenies. Except theacmAgene analysis, molecular tools revealed that isolates M78 and M104 clustered with strains of thecremorisgenotype, including the LMG 6897Tstrain, while they were distant from strains of thelactisgenotype, including the LMG 6890Tstrain. The two wild isolates had identical repetitive sequence-based PCR (rep-PCR), randomly amplified polymorphic DNA (RAPD), plasmid, and whole-cell protein profiles and shared high 16S rRNA (99.9%) andldh(100%) gene sequence homologies. In contrast, they exhibited identical sugar fermentation and enzymatic patterns which were similar to those of the subspecieslactisLMG 6890Tstrain. To our knowledge, this is the first complete identification report on a wildL. lactissubsp.cremorisgenotype of thelactisphenotype which is capable of nisin A production and, thus, has strong potential for use as a novel dairy starter and/or protective culture.
Characterization of a Wild, Novel Nisin A-Producing Lactococcus Strain with an L. lactis subsp.cremorisGenotype and an L. lactis subsp.lactisPhenotype, Isolated from Greek Raw Milk