Multi "omic" approaches will be combined to investigate the factors shaping the microbial communities in milks and traditional cheeses. Firstly, microbial diversity at species level will be explored across the 45 French PDO milks and cheeses, by metabarcoding sequencing. Secondly, focusing on six keystone species, the genomes of contemporary strains and of strains isolated from cheese up to several decades ago or from other biotopes will be compared in search of genetic traits of microbial species adaptation to the cheese context. Finally, profiling of microbial communities will be carried out by shotgun sequencing at the key stages of the manufacturing processes to understand the settling of keystone species and their specific gene expression in the time scale of cheese-making.