During the last decade, development of “omics” technologies has allowed us to gain insight into food bacteria and particularly to understand the behavior of Lactobacillus sakei during meat fermentation. Genome analyses reveal putative functions that may explain the adaptation of this species to the sausage environment and showed the wide intraspecies diversity. Post-genomics approaches, like proteomics and transcriptomics, and functional genomics or genetics were used to determine the functions important for Lact. sakei performance during meat fermentation or under conditions that may occur during meat processing. In parallel, genetic and molecular tool developments allowed us to investigate Lact. sakei physiology under sausage production conditions. A large genotypic and phenotypic diversity has been described within Lact. sakei. The chapter also outlines the main meat fitness traits of Lact. sakei as given by Eijsink and Axelson.