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A B Silaev

Publications and source records attributed to A B Silaev.

At least 37 records · Page 2Linked to original sources
PubMed1977

[Lysis of bacterial protoplasts and spheroplasts and suppression of their dehydrogenase activity by neotehomycin].

Neotelomycin induced lysis of the protoplasts of Bac. megaterium and inhibited their succinate dehydrogenase activity. Direct correlation between the lytic activity of the antibiotic and its effect on succinate dehydrogenase was found. Neotelomycin had no effect on the dehydrogenase activity of the protoplast lysates. Possibly, suppression of the protoplast succinate dehydrogenase of Bac. megaterium under the effect of neotelomycin was due to significant structural changes caused by the antibiotic in the protoplast membranes and leading to their lysis and not to the direct effect on the enzyme. Neotelomycin had practically no effect on the spheroplast dehydrogenase activity of E. coli resistant to the antibiotic and did not induce their lysis. Resistance of E. coli to neotelomycin must be associated not with the presence of the antibiotic non-permeable cell wall but the peculiar properties of the membrane cytoplasm.

Anti-Bacterial Agents↗
PubMed1977

[Source of valine for protein V biosynthesis in a producer of actinomycin C].

The specific activity of 14C-valine in valyl-tRNA formed during incubation of the actinomycin C-producing organism with 14C-valine was constant and lower than that of the whole cell pool. The constancy of the valyl-tRNA was indicative of the presence of a separate compartment for the valine pool used for protein biosynthesis. A lower specific activity of valine in valyl-tRNA as compared to that of the whole cell pool may be indicative of a low rate of valine metabolism in such separate compartment with exogenic 14-valine or a higher concentration of free valine in it as compared to the specific activity of this amino acid at average per cell.

Actinomyces↗
PubMed1976

[L-valine transport by the actinomycete Actinomyces species 26-115, the producer of actinomycin C].

Transport of L-valine by Actinomyces species 26-115, an organism producing actinomycin C depended on L-valine concentration in the medium and temperature and required a source of intrinsic energy. Km for L-valine transport was 3.5.10(-6)--6.0.10(-6) M. It somewhat differed from experiment to experiment. The above system transported also other neutral amino acids. L-isoleucine was a competing inhibitor of L-valine transport. The transport of L-valine was stereospecific. The activity of the transport system was regulated by the intracellular content of L-valine. Probably because of this the amino acid transport depended on the culture age, so far as the level of free valine in the mycelium at various stages of development was different.

Actinomyces↗
PubMed1976

[Heterogeneity of L-valine pool in Actinomyces sp. 26-115 producing actinomycin C].

Free intracellular valine in Actinomyces sp. 26-115 producing actinomycin C its functionally heterogenous. There are at least 2 pools of free valine. One of them supplies valine for protein biosynthesis and the second for the antibiotic biosynthesis. The volume of the pools is estimated. Inadequate reaction of the pools to similar effects is indicative of differences in their properties. The pool participating in protein biosynthesis strives for preservation of its volume. The pool participating in the antibiotic biosynthesis is capable of enlarging its volume to various levels depending on the change in the volume of the common intracellular pool.

Actinomyces↗
PubMed1976

[Study of the relationship of growth and morphological differentiation to antibiotic formation in heliomycin-producing cultures].

Relation between the growth of the heliomycin-producing organisms, biosynthesis of the antibiotic and morphological differentiation of the mycelium was studied. The curves of the culture growth were of diauxic nature. The synthesis of heliomycin was parallel to the organism active growth (trophophase). The antibiotic was synthesized in the germinating spores and localized in the areas of active growth and surface structures. The indicator properties of heliomycin were also evident in the organism mycelium. The antibiotic was registered in the young hyphae mainly in an oxidated form timed to the membrane structures. With the culture development heliomycin accumulated in the mycelium in reduced form together with lipids in the form of granules (vacuole structures). Condensation of heliomycin in the vacuoles (granules) started during the 2nd lag-phase, and may be associated with both heliomycin storing and inclusion of detoxication mechanisms. It was shown that heliomycin was consumed in the culture under conditions of starvation. In this case the antibiotic granules disappeared. The connection between the synthesis of heliomycin and the organism active growth, localization of the antibiotic in the areas of active growth, consumption of the antibiotic under conditions of starvation indicate that heliomycin is important for the organism and participates in the processes of growth and metabolism.

Anti-Bacterial Agents↗
PubMed1975

[Action of heliomycin on protein and mucleic acid synthesis in Staphylococcus aureus].

Heliomycin inhibited synthesis of RNA in Staph. aureua which was clearly shown in the study of the antibiotic effect on RNA synthesis in the lag phase of the culture development: heliomycin markedly lowered the maximum RNA level in the biomass observed in the culture at the beginning of the exponential growth. On further growth of the culture heliomycin induced a significant retardness of the process of the natural decrease in the RNA biomass level resulting in increased content of RNA in the cells growing in the presence of heliomycin as compared to the control culture. Retarded natural decrease in the RNA biomass level in the presence of heliomycin was observed also on the antibiotic addition just at the beginning of the exponential growth, during the period of maximum RNA accumulation in the cells. Heliomycin had no effect on synthesis and biomass levels of DNA. Heliomycin inhibited the protein synthesis and was close to chloramphenicol by the level of inhibition of the summation protein synthesis in the biomass. However, comparison of the effect of the above antibiotics on synthesis of beta-galactosidase, an individual enzyme protein showed that heliomycin was much less active as an inhibitor of protein synthesis in comparison to chloramphenicol.

Anti-Bacterial Agents↗
PubMed1975

[Spontaneous variability of antibiotic biosynthesis in relation to morphogenetic processes in Actinomyces chromogenes var. trienicus].

Available data on possible relationship between the antibiotic activity of actinomycetes and the level of their differentiation, especially with their spore-formation ability, present certain interest with respect to possible relationship between the synthesis of antibiotics and the formation of secondary structures. The study of spontaneous stable variants of Actinomyces chromogenes var. trienicus demonstrates that all sporogenous variants produce the same complex of antibiotics as does the original population. The loss of the ability to synthesize antibiotics is observed only in the phenotypically different dwarf variant (VI). The impaired differentiation (the loss of spore-formation ability) is accompanied by disturbances in the antibiotic synthesis: asporogenous variants are either inactive or produce only 1 antibiotic from the complex synthesized by the original population. Changes in the structure of spore chains do not probably correlate with qualitative and quantitative measurable changes in the antibiotic synthesis. The statistic evidence is suggestive of the fact that the variant with a more complex profile and topography of aerial mycelium displays a higher activity.

Streptomyces↗
PubMed1975

[Polymorphism of a culture of Actinomyces chromogenes var. trienicus, the producer of chromotrienine].

Variation of Actinomyces chromogenes var. trienicus 141-18 MSU, an organism producing trienin was studied under laboratory conditions. Nine stable spontaneous variants were isolated from the population of the initial culture when grown on Gause medium No. 1. The variants varied in differentiation and biosynthetic capacity, including such characteristics as size and form of the colonies, ability for formation of the aerial mycelium and its colour, capacity for sporulation, form of the spore chains and antibiotic production property. In the secondary structures the spores formed only in 6 variants out of 9 isolates. The spore form and spore membrane surface were close in all sporogenic variants, while there were significant differences in the structure of the sporophores. The variants forming the aerial mycelium of the same colour as that of the initial culture did not differ from it also by the nature of the spore chains (spirals with 3--8 turns). The variants with lighter aerial mycelium than that of the initial population formed straight sporophores or spirals with a small number of the turns (1--3). The comparative study of the antimicrobial spectrum of the variants and the component composition of the synthesized antibiotic complex showed that the asporogenic variants and dwarf variant signifcantly differed with respect to their phenotypes from the other cultures and had no antagonistic action. One of the assporogenic variants had only insignificant activity. All the spore forming variants did not differ from the initial culture in the complex of the antibiotics synthesized.

Actinomyces↗
PubMed1975

[Trichothecene inactivation by proteolytic enzymes from Trichothecium roseum Lk ex Fr].

Trichothecium roseum Lk ex Fr produces simultaneously trichothecin and proteolytic enzymes possessing fibrinolytic, thrombolytic and esterase activity. In addition to the function of splitting and consuming the substrate, the proteolytic enzymes of T. roseum are probably able to hydrolize the other bond in the molecule of trichothecin, which results in partial inactivation of the antibiotic in both the fungus culture and the model experiment on trichothecin contact with the preparations of the proteolytic enzymes. Presence of proteases of T. roseum may be considered as a protective mechanism for detoxication of the metabolites toxic for the organism.

Antifungal Agents↗
PubMed1975

[Polymorphism of a culture of the chromomycin producer, Actinomyces aburaviensis var. verrucosus].

Polymorphism of the chromomycin-producing orgnaism Act. aburaviensis var. verrucosus 144--3 was studied. The stable variants differed in the morphologo-cultural properties, assimilation of the carbon sources, the component composition of the luminescence substances and the quantitative property of the antibiotic production. A substance with violet luminescence was found in the culture of varient I in addition to chromomycin. Similarity of the phenotypes observed in variants 1 and 2 when grown on complex organic media is explained by intensive chromomycin production by variant 1 on such media. Active colonies may be selected according to the colour due to chromomycin. Forms with an activity almost 4 times higher than that of the initial culture were found among the colonies of variant 2.

Chromomycins↗
PubMed1975

[Action of heliomycin on the incorporation of labelled protein precursors and nucleic acid in Staphylococcus aureus cells].

In concentrations of 0.05-0.10 gamma/ml geliomycin suppresses inclusion of C14-uracyl into the acid-soluble fractions of the staphylococcal cells. Inclusion of C14-leucine at the same concentrations of the antibiotics was suppressed to a lesser extent. The above concentrations of geliomycin had practically no effect on inclusion of C14-thimine. Suppression of C14-uracyl inclusion was observed in 5 minutes of the cell incubation with the antibiotic, a significant decrease in C14-leucine inclusion being observed only in 30 minutes of the incubation. The effect of geliomycin on the staphylococcal cells within the concentrations inhibiting the microbial growth and suppressing inclusion of labeled uracyl and leucine into the cells was of the bacteriostatic nature. It was supposed that the antibacterial effect of geliomycin was based on suppression of RNA synthesis.

Anti-Bacterial Agents↗
PubMed1975

[Action of migillin on its own producer, Asp. fumigatus].

Addition of migillin to the nutrient medium at early stages of the fungus development induced at one hand inhibition of the fungus growth during the first 24-48 hours and stimulation of the biomass accumulation during the following hours of the development and on the other hand it induced inactivation of migillin added and inhibition of production of the "own" antibiotic. The migillin effect was accompanied by a delay in liberation of the substance with adsorption at 260nm from the mycelium.

Adsorption↗
PubMed1975

[Actinomycin DO inhibition of RNA biosynthesis and its interaction with DNA preparations].

Actinomycin D0 differing from actinomycin D in replacement of I residue of sarcosine by glycine in one of the peptide chains was found to have a lower inhibitory effect on RNA synthesis in various biological systems. On interaction of E. coli with DNA actinomycin D0 formed a complex with DNA having the binding constant K=1.6 with 10-5 which was 100 times lower than the binding constant of actinomycin D. Therefore, actinomycin D0 formed a complex with DNA which was 100 times less stable than actinomycin D. Actinomycins D0, D and II having different conformations in buffer on interaction with DNA formed complexes having similar conformations. The conformational change from free actinomycin to bound actinomycin was found difficult in case of actinomycin D0 because of its slow rate of complex formation with DNA as compared to that of other actinomycins complex formation with DNA.

Animals↗