METABOLIC-ACTIVITIES OF PSEUDOMONADS IN BATCH CULTURES IN EXTRACT OF MINCED LAMB

Pseudomonas fragi, Ps. lundensis and Ps. fluorescens were studied in a xenic batch cultures growing in a lamb juice (pH 6.0) aerobically or i n an atmosphere (Ps. fragi only) enriched with carbon dioxide at 4 deg rees C. With all but a glucose dehydrogenase-deficient strain of Ps. f luorescens there was a sequential catabolism of glucose and lactate. D iauxic growth was observed in a nutrient-deficient meat juice suppleme nted with glucose and lactate. A transient peak in the concentration o f gluconate and pyruvate was associated with the catabolism of glucose and lactate respectively. With Ps. fluorescens deficient in glucose d ehydrogenase there was simultaneous catabolism of glucose and lactate. The stereoisomers of lactate were catabolized simultaneously in a lab oratory medium. Glucose-6-phosphate was oxidized to 6-phosphogluconate by Ps. fragi and Ps. lundensis under aerobic conditions only. Creatin e and creatinine were catabolized by Ps. fragi under aerobic condition s only. There was a slight decrease in the concentration of total amin o acids (ninhydrin-reactive material) during the exponential phase of growth. The results suggest that the dominance of Ps. fragi in the cli max populations in meat is due to catabolism of amino acid related sub strates, creatine and creatinine.