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Mutant strains of Pseudomonas aeruginosa PAO were isolated on the basis of their inability to utilize mannitol as sole carbon source for growth. Four linkage groups (I through IV) among these mutant strains were resolved by twofactor crosses using the general transducing phage F116, and the strains appeared to contain point mutations as evidenced by ability to give rise to spontaneous revertants with wild phenotype on mannitol minimal agar. Group I strains were affected only in ability to grow on mannitol; all were deficient in inducible mannitol dehydrogenase activity, and all but one were deficient in inducible mannitol transport activity. Fructokinase was induced in group I strains and in wild-type bacteria during growth in the presence of mannitol but not fructose, indicating the presence of a pathway specific for endogenously generated fructose. Cells grown on fructose contained phosphoenolpyruvate:fructose-1-phosphotransferase activity, and mannitol-grown cells contained a lower level of this activity. Group II mutants were deficient in constitutive phosphoglucoisomerase, failed to grow on mannitol, grew very slowly on glycerol and fructose, but grew normally on glucose and gluconate. Group III strains were deficient in both nicotinamide adenine dinucleotideand nicotnamide adenine dinucleotide phosphate-linked glucose-6-phosphate dehydrogenase activities that reside in a single enzyme species. 6-Phosphogluconate appeared to be the inductive effector for this enzyme, which was not required for aerobic growth on glucose or gluconate. A single mannitol-negative mutant in group IV also failed to grow on glycerol and glucose, but no biochemical lesion was identified.

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Cell extracts of Bacillus licheniformis were found to contain nicotinamide adenine dinucleotide (NAD)-dependent L-alanine dehydrogenase (ADH) (Lalanine:NAD oxidoreductase, EC 1.4.1.1)'. High specific activities (3.5 to 6.0 IU/mg of protein) were found in extracts of cells throughout growth cycles only when L-alanine served as the primary source of carbon or carbon and nitrogen.Specific activities were minimal (0.02 to 0.04 IU/mg of protein) during growth on' glucose, but increased at least sevenfold during the first 5 h of postlogarithmicphase metabolism. Addition of 10 mM glucose to cultures during logkrithmicphase growth on L-alanine resulted in a rapid decrease in enzyme activity. Addition of 20 mM L-alanine to cells near the completion of log-phase growth on glucose resulted in a 20-fold increase in ADH specific activity during less than one cell generation. Extracts of postlogarithmic-phase cells cultured on glucose, malate, L-glutamate, or Casamino Acids contained intermediate levels of ADH activity. The enzyme was partially purified from crude extracts of B. licheniformis, and apparent kinetic constants were estimated. A role for ADH in the catabolism of L-alanine to pyruvate during vegetative growth on L-alanine and during sporulation of cells cultured on glucose is proposed on the basis of these experimental results. 59()on July 31, 2020 by guest

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