# Comprehensive Characterization of Five Lactococcus Strains: From Phenotypic Traits to Genomic Features

## TL;DR

This study analyzes five Lactococcus strains used in dairy fermentation, combining genomic and phenotypic data to understand their metabolic and phage resistance properties.

## Contribution

The study integrates whole-genome sequencing and phenotypic profiling to reveal strain-specific traits and phage resistance mechanisms in Lactococcus.

## Key findings

- Significant metabolic differences were found among genetically similar L. lactis strains.
- L. cremoris lacks the lacZ gene, affecting lactose metabolism.
- Prophages correlate with reduced acidification activity, and two strains show broad phage resistance.

## Abstract

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.