Comprehensive characterization of five Lactococcus strains: from phenotypic traits to genomic features

The efficiency of dairy product fermentation directly depends on the properties of the lactic acid bacteria used, particularly on their metabolic activity and resistance to bacteriophages. Therefore, an understanding of the relationships between the genetic and phenotypic traits of industrial strains is of elevated importance. In this study, we comprehensively analyzed five Lactococcus strains widely used in the Russian dairy industry, combining whole-genome sequencing with phenotypic profiling. Despite the fact of genetic similarity among four of the L. lactis strains, we still identified significant differences in their metabolic activity. Comparative structural analysis of previously published genomes of 337 L. lactis and 147 L. cremoris strains revealed species-specific features of the lactose metabolism; in particular, the absence of the lacZ gene in L. cremoris. Notably, prophages were found in three of the studied strains, which was in correlation with their reduced acidification activity. L. lactis FNCPS 51n and 73n strains displayed resistance to all 50 tested bacteriophages, which may be associated with the presence of the AbiB abortive infection system. These findings underscore the importance of integrating genomic and phenotypic analyses when selecting efficient and phage-resistant Lactococcus starters in the dairy industry.