Aeromonas salmonicida ssp. salmonicida requires exogenous arginine and methionine for growth

Griffin, Snieszko & Friddle (1953) developed a chemically defined medium for Aeromonas salmonicida ssp. salmonicida. This medium, which contained 44 compounds (including 17 amino acids), was later modified by O'Leary, Panos & Helz (1956), who reduced the number of compounds to 17 (including eight amino acids). In the present study, the authors describe a medium containing nine compounds (including two amino acids) in which A. salmonicida ssp. salmonicida can grow. The background for this study was the observation that a strain of A. salmonicida ssp. salmonicida could grow on a chemically defined medium, designated BM-medium [33 mM Na sub(2)HPO sub(4), 22 mM KH sub(2)PO sub(4), 20 mM NH sub(4)Cl, 10 mM NaCl, 1 mM MgSO sub(4), 0.1 mM CaCl sub(2), 10 mM glucose and 1.5% (w/v) Agar-Agar (Merek, Darmstadt, Germany)] supplemented with 1% (w/v) casamino acids (Sigma, St Louis, MO, USA). However, the strain did not grow if the casamino acids were omitted from the medium. To elucidate which amino acid(s) were essential, the strain was tested for growth on BM-media supplemented with combinations of the individual amino acids (0.25 mM of each). It was found that there was no growth when either arginine or methionine was omitted from the medium. This was confirmed by the observation that the strain could grow on BM-medium supplemented with arginine and methionine.