Lysogeny broth (LB) is a nutritionally rich medium primarily used for the growth of bacteria. Its creator, , intended LB to stand for lysogeny broth, but LB has also come to colloquially mean Luria broth, Lennox broth, life broth or Luria–Bertani medium. The formula of the LB medium was published in 1951 in the first paper of Bertani on lysogeny. In this article he described the modified and the isolation of the phages P1, P2, and . He had developed the LB medium to optimize Shigella growth and plaque formation.