NUTRITION AND PHYSIOLOGY OF PSEUDOMONAS FRAGI

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Abstract
A study of the utilization of a wide variety of C and N compounds by P. fragi served to define the nutritional requirements of this psychrophile and indicated some of the early precursors of the characteristic fruity aroma produced by the organism in dairy products. All of the Krebs cycle intermediates and related compounds tested produced good growth responses. Glucose, ribose, and gluconolactone were the only carbohydrates utilized. These data indicate the presence of the Krebs cycle and an alternate mechanism for glucose dissimilation in P. fragi. Although this organism gives a negative Voges-Proskauer reaction in complex media, biacetyl was detected when growth occurred in synthetic media containing fumarate, malate, oxalacetate, or pyruvate as C sources. Of the 30 N compounds studied, 28 elicited good growth responses. Arginine, histidine, glutamate, and alanine were suitable sources of both C and N. A characteristic aroma was detected in all cultures in which alanine, leucine, or glutamate was the C source or in which threonine was the N source.