Comparative genomics of Lactobacillus casei

The broad ecological adaptability of Lactobacillus casei facilitates widespread application of this organism in the food and health industries. To identify the genomic features of L. casei that contribute to evolution and lifestyle adaptation of the species, we performed comparative genomic analysis of 17 L. casei genomes representing strains isolated from dairy, plant, and human sources. Gene gain, via acquisition of genomic islands, likely confers a fitness benefit in specific habitats. The loss of unnecessary ancestral traits was especially pronounced in strains that show specialization for a cheese environment, where gene decay likely results in enhanced fitness in the dairy niche. This study gives the first picture of the L. casei pangenome and provides valuable insights into evolution and lifestyle adaptation of this important bacterium.