Generation of landomycin D-producing strainStreptomyces globisporus LD3

Rhodinosyl transferase gene lndGT4, governing the conversion of the disaccharide oligoketide ('polyketide') landomycin D into a trisaccharide derivative landomycin E, was deleted in Streptomyces globisporus 1912 genome. Possible resistance mechanisms that protect the resulting landomycin D-producing mutant strain S. globisporus LD3 against the toxic action of landomycins were determined.     

Activity of the System for Chlorophyll Biosynthesis and Structural and Functional Organization of Chloroplasts in a Plastome <Emphasis Type="Italic">en:chlorina-5</Emphasis> Sunflower Mutant

Chlorophyll (Chl) deficiency in leaves of a plastome sunflower (Helianthus annuus L.) en:chlorina-5 mutant is due to the formation of smaller chloroplasts with a markedly reduced membrane system, as compared to the parent 3629 line. Abnormalities in the structure of the photosynthetic apparatus in the mutant can be mainly attributed to changes in the formation of photosystem I and its light-harvesting complexes. Chl deficiency in en:chlorina-5 correlated with its lower capability of synthesizing the first specific Chl precursor, 5-aminolevulinic acid (ALA) in the light. Light-independent stages of Chl biosynthesis in the mutant had the same efficiency as in leaves of the parent line. ALA formation in darkness and its conversion into protochlorophyllide did not depend on the extent of photosynthetic membrane development and photosynthetic activity.     

Intergeneric Conjugation Escherichia coli–Streptomyces globisporus1912 Using Integrative Plasmid pSET152 and Its Derivatives

Streptomyces globisporus1912 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 fromEscherichia coliinto S. globisporus1912 has been developed. It was shown that this plasmid integrates into two sites of the S. globisporuschromosome 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 exconjugants was 120–150% of that in the original strain 1912. Based on pSET152, a vector system for gene knockouts in S. globisporuswas developed. The effectivity of this system was shown in the example of disruption of the lndAgene encoding the key enzyme of LE synthesis (-ketoacylsynthase). Inactivation of this gene was shown to lead to the cessation of LE biosynthesis.     

Genetic diversity of natural populations of Arabidopsis thaliana (L.) Heynh. in Karelia

The genetic structure of ten natural populations of Arabidopsis thaliana (L.) Heynh. at eight isozyme loci was studied. The populations were located in the northern part of the species range, 200 km from the north to the south along the Onega Lake coast in Karelia. Considerable genetic diversity (P99% = 43.7, Hobs = 0.003) was revealed that is not typical of populations of self-pollinating plant species. A direct correlation between the proportion of polymorphic loci and geographical latitude was shown (r = 0.68; P < 0.05). It is suggested that a high polymorphism level in Karelian Arabidopsis thaliana (L.) populations increasing from the south to the north is due to extreme environmental conditions in the northern part of the species range. The distribution of genetic diversity within and between populations is typical of self-pollinating species: the larger part of the total diversity resides among populations (GST = 0.583).     

Streptomyces ghanaensis pleiotropic regulatory gene wblA(gh) influences morphogenesis and moenomycin production

The wblA _gh gene, encoding a homologue of the WhiB-family of proteins, was identified in the sequenced genome of moenomycin producer Streptomyces ghanaensis. Deletion of the gene blocked aerial mycelium sporulation and caused a 230% increase in moenomycins production. S. ghanaensis overexpressing SSFG-01620: a homologue of extracellular protease inhibitor SCO0762, whose expression in Streptomyces coelicolor is down-regulated by wblA: showed deficiencies in sporulation similar to that of wblA _gh knockout strain. The wblA _gh gene of S. ghanaensis appears to play a negative role in the control of moenomycin biosynthesis and is essential for sporulation.     

Comparative analysis of genetic structure in natural populations of two Arabidopsis species with different degree of panmixia

Comparative analysis of genetic structure of northern natural populations of two Arabidopsis species with different degrees of panmixia was performed. The variability of 121 RAPD loci in seven populations of model plant A. thaliana possessing high degree of self fertility was studied together with 93 RAPD loci in population of cross-pollinating species A. lyrata ssp. petraea. The population of A. l. petraea demonstrated higher level of genetic variability (P 99% = 62.50%; H(exp) = 0.169) than the populations of A. Thaliana, which is obviously connected with biological features of reproduction of the species. A significant level of genetic variability (P 99% = 42.27%; H(exp) = 0.126) was revealed in populations of A. thaliana, which is not typical for self-pollinating plant species. The high population polymorphism of A. thaliana in the northern part of its range may be connected with adverse environmental conditions. The genetic distances between populations of the species studied (average DN = 0.494) confirm close relatedness between A. thaliana and A. l. petraea.     

Using intergenetic conjugation Escherichia coli-Streptomyces for transfer of recombinant DNA into S. nogalater IMET 43360 strain

Successful transfer of the studied plasmids into S. nogalater IMET43360 cells using bacterial conjugation in the system E. coli--Streptomyces is an appropriate method for constructing this strain. Using DNA-DNA hybridization the character of integration of pVWB and pRT801 plasmids has been studied. The influence of these plasmids on nogalamycin biosynthesis has been investigated as well. The obtained results enable detailed study of nogalamycin gene functioning in S. nogalater IMET43360. The use of conjugation for substitution, destruction of genes, and heterological expression allows to get new "hybrid" antibiotics produced by this strain.     

Proton-dependent transporter gene <Emphasis Type="Italic">lndJ</Emphasis> confers resistance to landomycin E in <Emphasis Type="Italic">Streptomyces globisporus</Emphasis> 1912

Sequence analysis of 2 kb BamHI-SmaI fragment of landomycin E (LaE) gene cluster in Streptomyces globisporus 1912 revealed one complete ORF marked as lndJ. Analysis of putative lndJ aminoacid sequence allowed us to suppose that it is proton-dependent antiporter which could be involved in resistance to LaE in the producing strain. Although disruption of lndJ had no significant influence on LaE production and resistance, its overexpression in wild type and LaE overproducing strains led to qualitative changes in landomycins biosynthesis and increased resistance to LaE. These data support the hypothesis about involvement of lndJ gene in landomycins export. The text was submitted by the authors in English.     

Hints for understanding microalgal phosphate-resilience from Micractinium simplicissimum IPPAS C-2056 (Trebouxiophyceae) isolated from a phosphorus-polluted site

Journal of Applied Phycology - A novel chlorophyte algae&nbsp;strain with outstanding resilience to high inorganic phosphate (Pi) concentrations in the medium was isolated from a...