Cytochemical and biological properties ofMycobacterium bovis BCG

It was the aim of the present communication to find a simple test for a reliable discrimination ofMycobacterium bovis BCG fromMycobacterium tuberculosis. A total of 26 BCG strains, out of them 10 Czechoslovak strains (2 lyophilized cultures of BCG of different batch, 6 strains isolated from abscesses of children after BCG-vaccination and 2 strains from fatal cases after BCG-vaccination) and 16 strains obtained from foreign laboratories, were used. Of the tested characteristics a combination of 3 tests, sensitivity to 1 μg of 2-thiophene carbonylhydrazide (TCH), activity of 3 acylamidases (urease, nicotinamidase and pyrazinamidase) and a quantitative nitrate test, was found to be most advantageous. The Czechoslovak strains ofMycobacterium bovis BCG were fully sensitive to TCH, of the 3 acylamidases mentioned above only urease was positive and nitrate was reduced only little or not at all. On the other hand, strains ofMycobacterium tuberculosis were always resistant to TCH, had positive urease, nicotinamidase and pyrazinamidase and reduced nitrate very intensively.     

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.     

Transforming activity of plasmid and chromosomal DNA inEscherichia coli

An auxotrophic strain ofEscherichia coli with therecB recC sbcB genotype was transformed by chromosomal DNA of the prototrophic strain and by plasmid DNA carrying genes for antibiotic resistance (R1drd 19). The donor plasmid DNA obtained by cell lysis in the presence of Triton X-100 and subsequent centrifugation in a caesium chloride-ethidium bromide gradient was shown to have a circulaf molecule and to retain its completeness after penetration into the recipient. Experiments with mixtures or plasmid and chromosomal DNA indicate a competition between these two DNA types during the transformation reaction in the given system.     

Inactivation by ammonia of the photosynthetic reduction of nitrate in Nostoc muscorum particles.

Ammonia, as well as other uncouplers of photophosphorylation, strongly inhibit the photosynthetic reduction of nitrate by particles of the blue-green alga Nostoc muscorum. The enzyme responsible for nitrate reduction, nitrate reductase, can be reversibly inactivated by reduction in a ferredoxin-dependent reaction. Nitrate protects against this inactivation, and molecular oxygen restores the original activity.     

Brassica campestris as a model for studying the effects of exogenous growth substances on flowering in long-day plants

Photoperiodic responses of seedlings of long-day plantBrassica campestris L. cv. Ceres were investigated at different ages and varying length of inductive period. It was found that photoperiodie response increased with age. All plants flowered after one inductive cycle beginning with a light-period of 16h, but remained in the vegetative phase when kept under short-days (16h darkness, 8h light). Both auxins (IAA and NAA) and cytokinins (kinetin and benzyladenine) inhibited flowering when applied to the plumule or via the roots immediately before the inductive photoperiod. This inhibitory effects was confined to bud formation, whereas the rate of leaf initiation remained mostly unchanged. Only high concentrations of growth substances also affected the growth of roots and leaves. These results agree, in general, with the effects of growth substances in the short-day plantChenopodium rubrum.