Growth of Legionnaires disease bacterium (Legionella pneumophila) in chemically defined medium

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Abstract
A chemically defined medium containing 21 amino acids and inorganic salts was developed which supported the growth of 4 isolates of Legionnaires disease bacterium (L. pneumophila). Growth in liquid defined medium at 37.degree. C with shaking approximated the generation time and growth kinetics observed for growth in complex media. After a 3-h lag, the culture grew exponentially with a generation time of 6 h and reached a maximum optical density of 230 Klett units (170 Klett units corrected for pigment). A soluble brown pigment was first observed as the culture entered late exponential to early stationary phase of growth. Morphologically, L. pneumophila grew in the liquid defined medium with extensive filamentation and numerous intracellular lipid granuoles. L-Serine, L-methionine and L-cysteine were required for optimum growth. The latter amino acid could be replaced by L-cystine or reduced glutathione but not by D-cysteine, thiomalate, thioglycollate or 2-mercaptoethanol. Ferric iron was needed for maximum growth, but supplemental Fe was not an essential growth requirement. Carbohydrates (i.e., glucose) or organic acids did not stimulate growth. Pyruvate, acetate and citrate all gave varying degrees of inhibition (69, 37 and 0% of control growth, respectively).

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