Some properties of pea enation mosaic virus isolated from field pea and broad bean plants in Bohemia

Pea enation mosaic virus (PEMV) was isolated from disea sed field pea (Pisum sativum L.ssp. arvense A.Gr.) and broad bean (Faba vulgaris Moench) plants grown as filed crops at Bohumilice in Bohemia. The virus proved to be pathogenic for the following plant species:Pisum sativum L. cv. Raman,Faba vulgaris Moench,Lens culinaris Med.,Vicia sativa L.,Lathyrus odoratus L.,Glycine soja L.,Phaseolus vulgaris L.,Chenopodium amaranticolor Coste andReyn,Nicotiana clevelandi Gray,Trifolium incarnatum L. The dilution end point of the isolate was higher in pea plants (10^?4) than in broad bean plants (10^?2). The thermal inactivation point was 65–68° and the longevityin vitro between 10 and 14 days. According to the host range, symptoms on pea plants and physical properties the virus isolate studied resembles some isolates described in the U.S.A. and represents a PEMV strain different from those reported so far in Czechoslovakia.     

Underground dry weight in the grassland communities ofArrhenatheretum elatioris alopecuretosum pratensis R. Tx. 1937 andMesobrometum erecti stipetosum Vicherek 1960

The meadow plant communities,Arrhenatheretum elatioris alopecuretosum pratensis R. Tx. 1937 andMesobrometum erecti stipetosum Vicherek 1960, were chosen for investigations of the underground plant parts. Apparent differences in underground dry weight and its seasonal changes in both the communities were observed. Differences in the soil environment in different periods of the year are reflected in the character of time changes in underground dry weight. The soil environment affects not only the total underground biomass and their changes in time, but also the activity of soil microflora and, consequently, the decomposition rate of dead underground plant parts.     

Antibacterially active substances

Synthesis of two hydroxy-derivatives of nalidixic acid as a result of microbial transformation was demonstrated in certain species of the genusAspergillus. Aspergillus alliaceus produced 7-hydroxy-nalidixic acid andAspergillus niger 6-hydroxy-nalidixic acid. It was demonstrated that the antibacterial activity of both hydroxy-derivatives (tested inEscherichia coli) was lower than that of the initial nalidixis acid.     

Physiological properties of microbial population as a basis for graphical solution of multi-stage continuous cultivations

A proposal for a graphical solution of the design of a multi-stage continuous culture system is presented. The holding times in individual stages are derived from the reciprocal values of the growth rate and of the product formation rate and plotted against the cell and product concentrations. Characteristic changes of physiologically significant paramaters are then projected on these production curves. Dedicated to Academican Ivan Málek on the occasion of his 60th birthday     

The effect of nucleosides on the induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli

The induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli starving for exogenous carbon and nitrogen sources was stimulated markedly by the addition of any of four nucleosides tested: adenosine, guanosine, cytidine, and uridine. Adenosine was used as a representative of this group of compounds in most experiments. The decrease of ability of the cells to synthesize β-galactosidase, resulting from a prolonged starvation for exogenous carbon and nitrogen, was removed by adenosine. This compound also considerably reduced the inhibitory effect of metabolic poisons on the induced synthesis of β-galactosidase. The blockade of induced β-galactosidase synthesis evoked in aerobically grown cells by anaerobic starvation for exogenous sources of carbon and nitrogen was also significantly reduced by adenosine. The weak transient catabolic repression of induced synthesis of β-galactosidase evoked by glucose in non-growing cells ofEscherichia coli deprived of exogenous carbon and nitrogen sources was prevented by adenosine. The total repression caused by higher glucose concentrations was not influenced by this compound. The results are discussed from the point of view of the role of the energy state ofEscherichia coli cells in the regulation of β-galactosidase synthesis.     

Effect of ethionine on the synthesis of β-galactosidase inEscherichia coli

Ethionine at concentrations of 10⁻³M, 5×10⁻³M and 10⁻²M inhibits growth, both of β-galactosidase inducible ML-30 and constitutive ML-308Escherichia coli strains. The protein synthesis (measured by the incorporation of l-leucine-¹⁴C and l-aspartic-¹⁴C acid into proteins) of these strains is inhibited to the same extent as their growth. The synthesis of inducible and constitutive β-galactosidase produced by the strains ML-30 and ML-308, respectively, is considerably inhibited by ethionine.     

Spores of microorganisms

6-Azauracil at a concentration of 1 μmole/ml inhibits by 50% the outgrowth of germinated spores of a strain ofBacillus cereus, concentration of 1.5 μmole/ml resulting in 100% inhibition. Two distinct maxima of sensitivity to 6-azauracil are observed during postgerminative development of spores. The first occurs during early stages of development (immediately after depolymerization period) and the second after about 60 min of cultivation (late stage of swelling). Uracil reverses the inhibition of the outgrowth of spores caused by 6-azauracil when added during 0–30 min of the spore development. The addition of uracil after 30 min of the germination does not bring about the reversion of the effect of 6-azauracil. An important role of pyrimidine pathway via orotidine 5′-phosphate in germinating spores was proved, suggesting a possible use of 6-azauracil in synchronization of the postgerminative development of spores.     

Use of Carbowax as a high molecular weight nonprotein substance for cultivation of lymphoid cell and study of their morphology

Lymphoid cells prepared from rabbit popliteal lymph nodes were cultivated in medium in which the high molecular weight component was replaced by Carbowax 20 M. This substance, in 0.2% concentration, proved to be a substitute for the high molecular weight component in short-term cultivation, and the viability results were similar to those in medium containing normal rabbit serum or 0.5% human serum albumin. In addition, mitoses and the formation of large basophilic cells resembling the blastoid cells induced during cultivation with phytohaemagglutinin were observed in this medium. The results are discussed.     

Secondary responsein vitro to antigen ΦX 174 phage

In a model secondary reactionin vitro, a correlation was demonstrated between the size of the antigen dose used for the prestimulation of spleen tissue donors and the type of antibodies formed in the anamnestic reaction. After a small dose of antigen ΦX 174, the antibody response three days after prestimulation was of the 19 S (IgM) type, but later secondary contactin vitro (after four months) did not produce a 19 S anamnestic reaction. After large primary doses of antigen, a short interval between primary and secondary contact led to the formation of 19 and 7 S type antibodies, while after a long interval only 7 S (IgG) type antibodies were formed. The results are discussed in relation to differences in the size of the antigen dose needed to induce short-term 19 S and long-term 7 S immunological memory.