Simultaneous and successive induction of synthesis of β-Galactosidase and tryptophanase inEscherichia coli K 12 in the chemostat

β-Galactosidase and tryptophanase were induced either simultaneously or successively during continuous cultivation of the inducible strainEscherichia coli K 12 in the chemostat. Growth was limited by glycerol and the dilution rate was 0.1 h⁻¹. During both the simultaneous and successive induction specific rates of synthesis, as well as maximum enzyme levels, were identical with those obtained after independent induction of individual enzymes. As compared with batch cultivation, β-galactosidase reached the same specific rate of synthesis in the chemostat, whereas the specific rate of synthesis of tryptophanase in the chemostat was up to five times higher.     

Effect of cyclic adenosine-3′,5′-monophosphate on the simultaneous synthesis of β-galactosidase and tryptophanase inEscherichia coli

When inducing simultaneously β-galactosidase and tryptophanase in a batch culture either the synthesis of tryptophanase or of both enzymes is decreased due to an insufficient cAMP concentration. The addition of this nucleotide can overcome this decrease. In a continuous culture both enzymes are synthesized at the maximum rate, as the amount of cAMP produced during carbon limitation of growth is probably sufficient for the simultaneous synthesis of both enzymes. In the β-galactosidase hyperproduction mutant cultivated continuously the level of β-galactosidase markedly decreases when tryptophanase is simultaneously induced. Also this decrease is caused by cAMP insufficiency and can be overcome by increasing its concentration. cAMP is thus an important regulatory factor of both enzymes and becomes a limiting factor in their simultaneous synthesis; a competition for this regulatory compound apparently occurs and probably also a different mutual affinity of the regulatory complex with the promoter site of the enzyme opérons is involved.     

Forage quality of leaf-fodder from the main broad-leaved woody species and its possible consequences for the Holocene development of forest vegetation in Central Europe

Leaf-hay was the principal winter feed of livestock from the Neolithic until the first archaeological records of scythes dated to the Iron Age (700–0 b.c.). Despite the use of meadow hay, leaf-fodder remained an important winter supplement until the present. Archaeological evidence lists Quercus, Tilia, Ulmus, Acer, Fraxinus and Corylus as woody species harvested for leaf-fodder, while Fagus, Populus or Carpinus were rarely used. The aim of our study was to test whether the use of listed woody species followed the pattern of their forage quality (syn. nutritive value). In late May 2012, we collected leaf biomass at four localities in the Czech Republic and determined concentrations of N, P, K, Ca, Mg, neutral- and acid-detergent fibre and lignin. Species with leaves of low forage quality were Carpinus betulus, Fagus sylvatica and Quercus robur, species with leaves of intermediate quality were Corylus avellana and Populus tremula and species with leaves of high quality were Ulmus glabra, Fraxinus excelsior, Tilia cordata and Acer platanoides. Selective browsing and harvesting of high quality species Acer, Fraxinus, Tilia and Ulmus thus probably supported their decline in the Bronze and Iron ages and supported the expansion of Carpinus and Fagus. Our results indicate that our ancestors’ practice of exploiting woody species as leaf-hay for winter fodder followed their nutritive value.     

Isolation ofEscherichia coli mutants with simultaneous hyperproduction of d-serine deaminase and β-galactosidase

Summary Double mutants ofE. coli hyperproducing D-serine deaminase and -galactosidase were isolated by two successive selection procedures in the chemostat. The specific activity of D-serine deaminase is 10 times higher and -galactosidase 5 times higher compared with the fully induced original strain B 28.     

Transport of acetylated sugars intoSaccharomyces cerevisiae RXII cells

The only acetylated sugar taken up bySaccharomyces cerevisiae RXII was 2,3,4,6-tetra-0-acetyl-β, D-glucopyranose and the only cells which took it up were those which grew under aerobic conditions and were harvested during the logarithmic phase of growth. The rate of the uptake of 2,3,4,6,-tetra-0-acetyl-β, D-glucopyranose was considerably slower than that of galactose and its “space” was approximately half the “space” of galactose. The results indicate that 2,3,4,6-tetra-0-acetyl-β, D-glucopyranose is transported into yeast cells by simple diffusion. The results of inhibition of growth ofSaccharomyces cerevisiae andEscherichia coli by 2,3,4,6-tetra-0-acetyl-β, D-glucopyranose are described. Inhibition differed in relation to the composition of the medium during cultivation.     

Morphological changes inEscherichia coli andBacillus cereus caused by external histone

It was found that the externally added histone changes remarkably both the surface and the internal ultrastructure of cells ofEscherichia coli. The interaction of histone with surface structures results in thickening of the inner layer of the cell wall. Cytoplasm becomes condensed, contains extensive electrontransparent zones and neither ribosomes nor the nuclear structure are differentiated. The addition of histone to germinating spores ofBacillus cereus decelerates germination and postgerminative development of this organism and changes ultrastructure of the external surface of the exosporium. The addition of Mg²⁺ ions reverting the effect of histone results in a renewal of the original ultrastruoture of the exosporium.     

Enzyme synthesis ofl-tryptophan

Enzyme synthesis of tryptophan from indole, pyruvate and ammonium salts was studied usingEscherichia coli cells exhibiting a significant tryptophanase activity. In addition to the effect of cultivation medium composition and cultivation conditions, factors affecting the course of the conversion were investigated. Production of 32.4 g/L ofl-tryptophan was reached after 48 h under optimal conditions.     

Intermittent high altitude--induced changes in energy metabolism in the rat myocardium and their reversibility

Selected enzyme activities of energy metabolism were studied in the myocardium of laboratory rats exposed to intermittent altitude hypoxia (IAH, 4-8 h daily, 5 days a week, in a hypobaric chamber, stepwise up to 7,000 m). No significant differences were found between the right and the left ventricle in the control animals. Glucose-utilizing capacity (HK) and capacity for the synthesis and degradation of lactate (LDH) increased significantly in both ventricles during acclimatization. The other enzyme activities associated with anaerobic glycolysis (TPDH, GPDH) and those linked up in aerobic metabolism (MDH, CS) did not change significantly. On the other hand, the ability to break down fatty acids (HOADH) decreased significantly. All the above changes in the enzyme profile were found after only 24 4-h exposures, in both the hypertrophic right ventricle and the unenlarged left ventricle. When the length of daily exposure was raised from 4 to 8 h, the above changes were not intensified and 45 days after the last exposure to IAH, none of the given activity values differed from those estimated in the corresponding control animals.