No abstract

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.

The effects of various carbon sources, phosphorus concentration, and different concentrations of the micronutrients calcium, cobalt, copper, iron, manganese, potassium, and zinc were determined on biomass dry weight production, geosmin production, and geosmin/biomass (G/B) values for Streptomyces halstedii, a geosmin-producing actinomycete isolated from the sediment of an aquaculture pond. Of the substrates tested, maltose as a sole carbon source promoted maximal growth by S. halstedii while mannitol promoted maximal geosmin production, and galactose yielded the highest G/B values. Fish-food pellets and galactose were poor substrates for growth. Increasing phosphorus concentrations enhanced geosmin production and G/B values. Of the seven micronutrients tested, zinc, iron, and copper had the most profound effects on biomass and geosmin production. Increasing zinc concentrations promoted biomass production while inhibiting geosmin production and G/B values; increasing concentrations of copper and iron inhibited biomass and geosmin production. Increased copper concentrations had the greatest effect in preventing growth and geosmin production by S. halstedii.

1993. Geosmin-producing species of Streptomyces and Lyngbya from aquaculture ponds. Can. J. Microbiol. 39: 834-840. Water and sediment samples collected monthly from six aquaculture ponds in east-central Alabama were analyzed for the presence of actinomycetes and cyanobacteria capable of producing geosmin and (or) 2-methylisoborneol, which cause earthy-musty off-flavors in fish. Six actinomycetous isolates were identified as geosmin producers, five of which were capable of producing 2-methylisoborneol. The one actinomycetous isolate producing geosmin but not 2-methylisoborneol was identified as Streptomyces halstedii. Only one of several cyanobacterial isolates was found to produce geosmin. This isolate was identified as Lyngbya cf. subtilis and was prevalent throughout the sampling period in a pond with a history of off-flavor problems. None of the cyanobacterial isolates produced 2-methylisoborneol in laboratory culture.

Mutants of Pseudomonas aeruginosa, strain PAO, have been isolated that are unable to grow on mannitol, glucose, gluconate, or 2-ketogluconate, but 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 of each mutant strain recovered 6-phosphogluconate dehydratase activity, and 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. compounds. Although a role for the pentose phosphate pathway in the catabolism of C. substrates was not found, a functional Entner-Doudoroff pathway appears to be essential for the catabolism of mannitol, glucose, gluconate, and 2-ketogluconate.

A clinical isolate and a soil isolate of Chromobacterium violaceum were compared to determine differences in virulence-related characteristics. Purified lipopolysaccharide (endotoxin) from the virulent, clinical strain was more reactive than that from the avirulent soil strain as determined by the Limulus amebocyte lysate assay. There were no differences in hemolysin or cyanide production between the two strains. The virulent strain was more resistant to phagocytosis and intracellular killing by human polymorphonucleocytes. The clinical strain showed a superoxide dismutase activity 30% higher and a catalase activity fivefold higher than the activities of the soil-isolated strain. The clinical strain also was capable of producing approximately twice as much hydrogen peroxide during growth as compared with the soil isolate. This study suggests that virulence of C. violaceum may be, at least in part, associated with endotoxin, and some protection of the virulent, clinical strain from phagocytic attack is afforded by elevated levels of superoxide dismutase and catalase.

Cell extracts of Pseudomonas aeruginosa strain 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 compounds. Methods for the isolation and characterization of mutant strains deficient in pyru-999 on July 31, 2020 by guest

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 14 CO 2 incorporation 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. 14 CO 2 was incorporated into pyruvate when propionate and n -propylamine were oxidized in the presence of NaAsO 2 , 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 14 CO 2 incorporation studies with several propane-utilizing organisms indicate that the methylmalonyl-succinate pathway is the predominant one for the metabolism of propionate.