Guanine is a growth factor for Legionella species.

Evaluation of previously described chemically defined media for the growth of Legionella pneumophila showed that these media supported poor growth of several strains of L. pneumophila and did not support growth of certain of the Legionella species described later. Growth was stimulated by the dialysate from yeast extract but not by the nondialyzable fraction. Further investigations indicated that the active factors from the yeast extract dialysate were purine or pyrimidine derivatives, and certain known purines and pyrimidines were found to stimulate growth. Of these, guanine universally stimulated growth of all Legionella strains and was a growth requirement for several of the species tested. A balanced, N-(2-acetamido)-2-aminoethanesulfonic acid-buffered, chemically defined medium having guanine or a purine-pyrimidine mix is presented for the general growth of Legionella species.