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Donor deoxyribonucleic acid extracted from streptomycin-resistant (StrR) mutant derivatives of a variety of strains of Streptococcus mutans, S. salivarius, and S. sanguiswas used to transform streptomycin resistance into competent S. sanguisstrain Challis. Transfer of genetic markers for sorbitol and mannitol fermentation and for extracellular polysaccharide as demonstrated by colonial morphology was not detected in this study. Reciprocal transformation between strain Challis and other oral streptococci could not be demonstrated. Transformation frequencies for StrRwere relatively efficient among S. sanguisstrains, with lower but significant frequencies demonstrated with strain Challis and donor deoxyribonucleic acid derived from other oral streptococci.

Mutant strains of Pseudomonas aeruginosaPAO 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 two-factor 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 dinucleotide- and nicotinamide 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.

Mutants of Pseudomonas aeruginosa, strain PAO, have been isolated that are unable to grow on mannitol, glucose, gluconate, or 2-ketogluconate, cut that exhibit wild-type growth on pyruvate, lactate, citrate, succinate, or acetate. Although some of these mutants were also unable to grow on glycerol, the mutations formed a single linkage group by quantitative transductional analysis with phage F116 on glucose minimal agar medium. Cell extracts of all mutant strains were either lacking or severely deficient in 6-phosphogluconate dehydratase activity. Glu+ transductants derived from mutant strains that retained the wild-type ability for growth at the expense of glycerol also regained the ability to grow on all C-6 compounds. Although a role for the pentose phosphate pathway in the catabolism of C6 substrates was not found, a functional Entner-Doudoroff pathway appears to be essential for the catabolism of mannitol, glucose, gluconate, and 2-ketogluconate.

Cell extracts of Pseudomonas aeruginosastrain PAO were found to contain pyruvate carboxylase activity. Specific activities were minimal when cells were grown on Casamino Acids, acetate, or succinate, but were three- to fourfold higher when cells were grown in glucose, gluconate, glycerol, lactate, or pyruvate minimal media. The reaction in crude cell extracts and in partially purified preparations was dependent on pyruvate, adenosine 5′-triphosphate, and Mg2+, but was not affected by either the presence or absence of acetyl coenzyme A. Activity was nearly totally inhibited by avidin and this inhibition was substantially blocked by free biotin in incubation mixtures. Cell extracts were shown to fix 14CO2in a reaction that had these same characteristics. Eight pleiotropic, carbohydrate-negative mutant strains of the organism were isolated after nitrosoguanidine mutagenesis. Each mutant strain grew normally in acetate, succinate, and citrate minimal media but failed to utilize glucose, gluconate, 2-ketogluconate, mannitol, glycerol, lactate, and pyruvate as sole sources of carbon and energy. These strains were found by quantitative transductional analysis with phage F116 to form a single linkage group. Cell extracts of each mutant strain were either lacking or severely deficient in pyruvate carboxylase activity. Spontaneous revertants of five of the eight strains were isolated and found to recover simultaneously both pyruvate carboxylase activity and the ability to utilize each of the C6and C3compounds. A second linkage group of similar mutant strains that grew on the C3compounds was found to contain normal levels of pyruvate carboxylase activity, but each strain was deficient in an enzyme of the Entner-Doudoroff pathway.

Studies were conducted on the oxidation and assimilation of various three-carbon compounds by a gram-positive rod isolated from soil and designated strain R-22. This organism can utilize propane, propionate, or n-propylamine as sole source of carbon and energy. Respiration rates, enzyme assays, and 14CO2incorporation experiments suggest that propane is metabolized via methyl ketone formation; propionate and n-propylamine are metabolized via the methylmalonyl-succinate pathway. Isocitrate lyase activity was found in cells grown on acetate and was not present in cells grown on propionate or n-propylamine. 14CO2was incorporated into pyruvate when propionate and n-propylamine were oxidized in the presence of NaAsO2, but insignificant radioactivity was found in pyruvate produced during the oxidation of propane and acetone. The n-propylamine dissimilatory mechanism was inducible in strain R-22, and amine dehydrogenase activity was detected in cells grown on n-propylamine. Radiorespirometer and 14CO2incorporation studies with several propane-utilizing organisms indicate that the methylmalonyl-succinate pathway is the predominant one for the metabolism of propionate.