Bacteriocin Antagonistic Potentials of Lactococcus cremoris and Lactococcus lactis Isolates from Different Habitats

It has not been extensively examined if the ecological role of lactic acid bacterial bacteriocins may affect their distribution in different habitats and thereby impact screenings for novel variants. Further, the functionality of such variants requires additional investigation. This study investigated the distribution of bacteriocin biosynthetic gene clusters (BGCs) and bacteriocinogenic activity of Lactococcus cremoris and Lactococcus lactis from a range of different environments. Whole genome sequencing and phylogenetic analysis of fifty L. cremoris and L. lactis strains showed distinct species clustering without significant genome size differences between species or sources. Genomic screening with AntiSMASH and BAGEL4 identified several BGCs, with variation based on species but not on habitat. Deferred inhibition assays revealed pronounced activity only in strains possessing nisin or lactococcin B BGCs and not in strains with other BGCs. Several hitherto undescribed types of lactococcin BGCs appeared to be incomplete regarding genes encoding secretion and immunity. In conclusion, this study indicates that habitats did not appear to affect distribution of BGCs. Further, the antagonistic functionality of several BGCs was unclear indicating that improving applications of lactococcal bacteriocins may depend as much or more on research on increasing efficacy of well-known bacteriocins than searching for novel variants.