[Generation and study of the strains of streptomycetes--heterologous hosts for the production of moenomycin].

In this paper, we report the generation of a number of novel heterologous streptomycete hosts producing nosokomycin A2 (one of the members of Mm family) and determine their potential for antibiotic production. The rpoB point mutation in the model strain of Streptomyces coelicolor (strain M1152) significantly improved nosokomycin A2 production compared to parental strains (M145 and M512), while double rpoBrpsL mutation in the same species (strain M1154) decreased it. Our results point to the previously unanticipated epistatic interactions between mutations that individually are known to be highly beneficial for antibiotic production. We also showed for the first time that facultative chemolitotrophic streptomycete S. thermospinosisporus and chloramphenicol producer S. venezuelae can be used as the hosts for moe genes.

[Design of Streptomyces nogalater LV65 strains with higher synthesis of nogalamicin using regulatory genes].

Influence of cloned regulatory genes on biosynthesis of nogalamicin by Streptomyces nogalater LV65 strains has been studied. Gene snorA from the S. nogalater genome was cloned in multicopy replicative plasmid pSOKA and integrative plasmid pR3A. Introduction of these plasmids into the cells of wild type strain of S. nogalater LV65 resulted in higher synthesis of nogalamicin. A similar effect was observed at heterologous expression of gene ppGpp of synthetase relA cloned in S. coelicolor A3(2). Heterologous expression of genes absA2from S. ghanaensis ATCC14672 and lndyR from genome S. globisporus 1912 decreased synthesis of antibiotic. The study results indicate the presence of homologs of these genes in chromosome of S. nogalater, their possible participation in regulation of nogalamicin biosynthesis, and provide us with a possibility for genetic design of the strains with higher synthesis of this antibiotic.

[Diversity of genes encoding nonribosomal peptide synthetases in the Streptomyces sioyaensis genome].

Streptomyces sioyaensis Lv81 produces siomycin, a thiopeptide antibiotic synthesized on ribosomes. Nothing is known about the ability of this strain to produce nonribosomal peptides, a well represented group of natural actinomycete compounds. Using degenerate primers, we cloned a number of DNA fragments encoding putative adenylation domains (A domains) of nonribisomal peptide synthetases involved in biosynthesis of unknown compounds. Sequencing of amplicons revealed nine different A domains, which were analyzed in more detail. Nonribosomal codes of these domains were determined, but in most cases their substrate specificity failed to be unambiguously predicted. This means that many of these domains can recognize novel amino acids and be used to improve and expand the bioinformatic toolbox applied to predict substrate specificity of A domains. Multiple sequence alingments showed that the cloned A domains are probably involved in different biosynthetic pathways. Five A domains were used in gene inactivation experiments. Inactivation of one of them (in strain 736) resulted in a decrease of the total antibiotic activity as compared to the initial strain. Other A-domain mutants were similar to the initial strain in morphology and siomycin production. The causes of reduced antibiotic activity of strain 736 are discussed.

[The use of PCR for detecting genes that encode type I polyketide synthases in genomes of actinomycetes].

PCR screening of type I polyketidesynthase genes (PKS) was conducted in genomes of actinomycetes, producers of antibiotics. Some DNA fragments from the Streptomyces globisporus 1912 strain, a producer of a novel angucycline antibiotic landomycin E, were amplified. These fragments shared appreciable homology with type I PKS controlling the biosynthesis of polyene antibiotics (pymaricin and nistatin). The cloned regions were used to inactivate putative type I PKS genes in S. globisporus 1912. Strains with inactivated genes of PKS module do not differ from the original strain in the spectrum of synthesized polyketides. Apparently, these are silent genes, which require specific induction for their expression. The method of PCR screening can be used in a large-scale search for producers of new antibiotics.

[Effect of glucose on the antibiotic activity and antibiotic resistance of Streptomyces peucetius subsp. caesius ATCC 27952-2 and its mutants]. / Vliianie gliukozy na antibioticheskuiu aktivnost' i ustoichivost' k antibiotikam Streptomyces peucetius subsp. caesius ATCC 27952-2 i ego mutantov.

The growth of anthracycline producer Streptomices peucetius subsp. caesius ATCC 27952-2 was inhibited by presence of glucose on complete media, containing alternative carbon sources. Amount of clones not producing antibiotic increased to 80.2 per cent along with elevation of glucose concentration in corn meal medium from 0.1 to 1.0 per cent. Mutants of S. peucetius subsp. caesius ATCC 27952-2 able to grow on complete media with 2 per cent of glucose (glr-mutants) were obtained. Glr-mutants had decreased antibiotic production in comparison with 27952-2 strain. 17 per cent of studied glr-mutants synthesized 1.6-3.1-fold quantities of anthracyclines in comparison with parental strain. Glr-mutants synthesized more biomass, although more slowly utilized glucose than strain 27952-2.

[Interspecies conjugation of Escherichia coli-Streptomyces globisporus 1912 using integrative plasmid pSET152 and its derivatives]. / Mezhrodovaia kon''iugatsiia Escherichia coli-Streptomyces globisporus 1912 s ispol'zovaniem integrativnoi plazmidy pSET152 i ee proizvodnykh.

Streptomyces globisporus 1912 produces a novel angucycline antitumor antibiotic landomycin E (LE). To study the LE biosynthetic gene cluster in detail, a system for the conjugal transfer of the integrative plasmid pSET152 from Escherichia coli into S. globisporus 1912 has been developed. It was shown that this plasmid integrates into two sites of the S. globisporus chromosome and is stably inherited under nonselective conditions. pSET152+ exconjugants of the strain 1912 are characterized by a significant decrease in LE synthesis (by 50-90%). A negative effect of pSET152 integration on antibiotic production was observed even upon the use of the recipient strain with increased LE synthesis, although in this case, the level of LE production in ex-conjugants was 120-150% of that in the original strain 1912. Based on pSET152, a vector system for gene knockouts in S. globisporus was developed. The effectivity of this system was shown in the example of disruption of the lndA gene encoding the key enzyme of LE synthesis (beta-ketoacylsynthase). Inactivation of this gene was shown to lead to the cessation of LE biosynthesis.

[Isolation and characterization of Saccharopolyspora erythraea mutants, resistant to chloramphenicol]. / Poluchenie i kharakteristika mutantov Saccharopolyspora erythraea, ustoichivykh k khloramfenikolu.

Formation of chloramphenicol resistant (CMr) spontaneous and nitroso-ethyl-urea-induced mutants of S.erythraea, an organism producing erythromycin, was studied. The mutants differed by the level of the chloramphenicol resistance (10 to 40 micrograms/ml). Part of the chloramphenicol resistance mutations had a pleiotropic pattern. 63.8 per cent of the CMr mutants was characterized by the growth thermosensitivity and 18.9 per cent was characterized by the absence of the melanin production property. The antibiotic potency of 56 per cent of the CMr mutants was higher than that of the initial strain. In some of the CMr mutants the property of resistance to other antibiotics was changed. A higher resistance of some mutants to chloramphenicol correlated with their increased lincomycin resistance. It was shown that chloramphenicol induced resistance to kanamycin in S.erythraea 5. Such a property for the resistance induction was preserved in the spontaneous low CMr mutants while the high CMr mutants isolated after the culture exposure to the mutagen lacked it. The CMr S.erythraea phenotype was genetically instable. Two different amplifying DNA sequences (18 and 70-78 kb in size) were detected in the CMr mutant genome. The chloramphenicol resistance mutation was localized in the S.erythraea chromosome region restricted by markers ura1 and met1.

[Analysis of genome rearrangements in Streptomyces kanamyceticus mutants]. / Analiz perestroek genoma u mutantov Streptomyces kanamyceticus.

Studies with the use of pulsed electrophoresis showed that Asel and Dral restriction endonucleases segregated chromosomal DNA of the initial strain Streptomyces kanamyceticus 1 into 16 and 12 fragments, respectively. The total size of the strain chromosomal DNA was from 7715 (the total of the Dral fragment sizes) to 7788 kb (the total of the Asel fragment sizes). Chromosomal DNA rearrangements were detected in the unstable Kan- mutant kan12 as well as in mutant genR10 which was characterized by higher resistance to kanamycin and gentamicin. As compared to DNA of the initial strain S.kanamyceticus 1 and the stable mutant kanC782, mutant kan12 lacked 98-kb and 220-kb Asel fragments and contained additional 297-kb and 450-kb fragments. DNA of genR10 lacked 420-kb Asel fragment but contained an additional 450-kb fragment. Kan12 and genR10 as well as two more mutants (genR8 and genR8.1) resistant to the above antibiotics contained amplifications of gene kmr determining resistance of S.kanamyceticus 1 to kanamycin. The most intensive amplification was detected in the most resistant mutant genR8.1.

Magnetoacoustic SAW interaction in YIG films.

The magnetoacoustic SAW interaction has been experimentally investigated for yttrium-iron garnet films placed on gallium gadolinium garnet substrates. In this paper, we propose a new approach to the analysis of hysteresis dependencies which consist of two branches for different directions of magnetic field variation. For each of the branches, even and odd portions were separated. The even portions were shown to be related to magnetostriction and the odd ones to DeltaE-effect and magnetostriction linearized internal magnetic field of domains.

[The isolation and characteristics of mutants of the Saccharopolyspora erythraea strain resistant to thiostrepton]. / Poluchenie i kharakteristika mutantov shtamma Saccharopolyspora erythraea, ustoichivykh k tiostreptonu.

The formation of thiostreptone resistant spontaneous and nitrosoguanidine-induced mutants in the erythromycin-producing organism Saccharopolyspora erythraea was investigated. The investigated collection of the mutants was heterogeneous by the level of the thiostreptone resistance (2.5 to 20 micrograms/ml). The thiostreptone resistance mutations had a pleiotropic effect: 17 per cent of the mutants was characterized by the growth thermosensitivity and 26 and 5.8 per cent of the mutants were characterized by loss of the ability to form melanine and aerial mycelium respectively. Such phenotypes were most frequent in the mutants resistant to low concentrations of thiostreptone (2 to 5 micrograms/ml). The absolute majority of the isolated thiostreptone resistant mutants was unstable and formed both the antibiotic resistant and the antibiotic sensitive clones. The greatest portion of the strains with high antibiotic activity (20 per cent) was detected among the S. erythraea spontaneous mutants on the medium with 2.5 micrograms/ ml of thiostreptone. It was shown that the instability of the high antibiotic activity in the mutants was associated with loss of the thiostreptone resistance property.

[Metabolites produced by Streptomyces kanamyceticus mutants with impaired biosynthesis of kanamycin]. / Metabolity, obrazuemye mutantami Streptomyces kanamyceticus s narushennym biosintezom kanamitsina.

Metabolites produced by Streptomyces kanamyceticus mutants with impaired kanamycin biosynthesis (kan mutants) were investigated by thin layer chromatography. With spectrophotometric scanning of the chromatograms the quantitative content of kanamycin A and 2-desoxystreptamine (2-DOS) in the culture fluid was determined. Five groups of the S.kanamyceticus mutants with impaired kanamycin biosynthesis at various stages were identified: kanA produced no D-glucosamine, kanB and kanC produced no 2-DOS, kanD was not able to transfer 2-DOS to the metabolites with the antibiotic activity, kanG synthesized no kanosamine.

[Kanamycin biosynthesis and aminoglycoside resistance in mutants of Streptomyces kanamyceticus resistant to 2-deoxyglucose]. / Kharakteristika mutantov Streptomyces kanamyceticus, ustoichivykh k aminoglikozidnym antibiotikam.

Mutants of S. kanamyceticus resistant to 2-desoxy-D-glucose (2-DOG) with impaired glucose repression of the kanamycin biosynthesis property were isolated. The effect of the carbon sources such as glucose, sucrose, maltose and glycerol on the biosynthesis of kanamycin by the mutants was studied in comparison to the wild type strain 1375 and strain 1, an improved variant with higher levels of kanamycin production. Significant differences in the level of kanamycin biosynthesis by the strains grown in the presence of the carbon sources were detected. Unlike the initial strains of S. kanamyceticus, the mutants resistant to 2-DOG synthesized kanamycin in the presence of high concentrations of glucose in the medium (2 or 5 per cent). Strains 1375, 1 and dgrl of S. kanamyceticus significantly differed by the rate of the glucose utilization. The rate of the glucose utilization by the highly productive strain 1 and 2-DOG resistant mutant was lower than that by the wild type strain 1375. Expression of the aminoglycoside resistance feature in the mutants with the impaired repression of the kanamycin biosynthesis property was studied in comparison with that in the initial strains of S. kanamyceticus. It was demonstrated that the mutants differed in the level of the resistance to their own and other aminoglycoside antibiotics.

[Characteristics of Streptomyces kanamyceticus mutants resistant to aminoglycoside antibiotics]. / Kharakteristika mutantov Streptomyces kanamyceticus, ustoichivykh k aminoglikozidnym antibiotikam.

The influence of the antibiotic activity level in strains of S. kanamyceticus on their resistance to kanamycin and other aminoglycosides was studied. Correlation between the activity of the strains and their resistance was observed. A collection of induced mutants of S. kanamyceticus with increased resistance to kanamycin, gentamicin, neomycin and apramycin was set. Cross resistance in the mutants to the aminoglycosides under different conditions (fermentative and not fermentative) was characterized. An increase in the resistance to gentamicin, neomycin and apramycin correlated with an increase in the resistance to kanamycin. The effect of the mutations of resistance to the aminoglycosides on the antibiotic activity of S. kanamyceticus was investigated. It was found that the population of the gentamicin resistant mutants was characterized by an increased average antibiotic activity and a higher number of the plus variants which is promising for the improvement of the strains with respect to higher levels of the kanamycin synthesis. The dynamics of the kanamycin synthesis in the initial strain of S. kanamyceticus was compared with that in its aminoglycoside resistant mutants. The apramycin resistant mutant was characterized by a significant delay in the beginning of the kanamycin synthesis.

[Isolation and study of the properties of Streptomyces kanamyceticus mutants with disorders of kanamycin biosynthesis]. / Poluchenie i izuchenie svoistv mutantov Streptomyces kanamyceticus s narusheniiami biosinteza kanamitsinov.

The strains of Streptomyces kanamyceticus 1375 and 1 were exposed to N-nitroso-N-methyl urea, ethidium bromide and acriflavine and mutants with impaired biosynthesis of kanamycin (Kan-) were isolated. The majority of the mutants were genetically unstable and segregated with the formation of both the Kan- and Kan+ clones. The stable Kan- mutants were tested in pairs for the cosynthesis. The capacity of the mutants for the recovery of the kanamycin synthesis in media supplemented with kanamycin precursors such as 2-desoxystreptamine and D-glucoseamine was studied. Four classes of the Kan- mutants involving various genes controlling the kanamycin biosynthesis in S. kanamyceticus were identified by the results of the tests.

[Isolation and characterization of genetic recombinants in protoplast fusion in Saccharopolyspora erythraea]. / Poluchenie i kharakteristika geneticheskikh rekombinantov pri sliianii protoplastov Saccharopolyspora erythraea.

Formation of genetic recombinants after conjugation and protoplast fusion in Saccharopolyspora erythraea, an organism producing erythromycin, was studied comparatively. After the protoplast fusion the frequency of all the classes of the haploid recombinants increased 10 to 460 times by comparison with the conjugation. The protoplast fusion was characterized by higher diversity of the recombinant classes, up to 45.5 per cent of the recombinants being formed at the account of multiple crossing overs. It was shown that unlike conjugation of the S. erythraea strains the protoplast fusion had no gradient of inheritance of the parent genetic markers by the recombinants. The results indicated that in S. erythraea protoplast fusion the recombination involved more genes of the parent strains. This makes promising the procedure for genetic analysis and design of erythromycin-producing strains.

Synchronism of the siberian traps and the permian-triassic boundary.

Uranium-lead ages from an ion probe were taken for zircons from the ore-bearing Noril'sk I intrusion that is comagmatic with, and intrusive to, the Siberian Traps. These values match, within an experimental error of +/-4 million years, the dates for zircons extracted from a tuff at the Permian-Triassic (P-Tr) boundary. The results are consistent with the hypothesis that the P-Tr extinction was caused by the Siberian basaltic flood volcanism. It is likely that the eruption of these magmas was accompanied by the injection of large amounts of sulfur dioxide into the upper atmosphere, which may have led to global cooling and to expansion of the polar ice cap. The P-Tr extinction event may have been caused by a combination of acid rain and global cooling as well as rapid and extreme changes in sea level resulting from expansion of the polar ice cap.

[Amplifying sequences in the Streptomyces coelicolor A3 (2) gene]. / Amplifitsiruiushchiesia posledovatel'nosti v genome Streptomyces coelicolor A3 (2).

The unstable feature of ristomycin resistance in S. coelicolor A3 (2) was studied. It was shown that the frequency of ristomycin-resistant derivatives was high in both chloramphenicol sensitive mutants and their resistant revertants. The 15- and 20-kb DNA sequences capable of amplifying were detected in the chloramphenicol resistant revertants. In the genomes of the studied strains they were represented by 50 and 40 copies, respectively.