Comparative study of various methods for determining Vibrio cholerae toxigenicity

Testing of 138 Vibrio cholerae strains for gene determinants responsible for the production of cholera enterotoxin by the polymerase chain reaction (PCR) and gene probing using molecular CT-probe showed good correlation of the results of different methods and correlation of these data with studies of V. cholerae strain virulence in vivo and in hemolytic activity test. The advantages of PCR in rapid assessment of the toxigenicity and epidemic significance of V. cholerae strains are demonstrated.     

Studying genetic diversity in inbred sunflower lines by RAPD and isoenzyme analyses

Genetic diversity of 30 inbred sunflower lines was examined by RAPD and isozyme analyses. The inbred lines were shown to be highly polymorphic by RAPD markers. The line distribution on genetic similarity dendrograms based on the RAPD and isozyme data was analyzed. High effectiveness of RAPD analysis for differentiating genotypes of inbred sunflower lines was demonstrated.     

Mutants of the nitrogen-fixing rhizospheric bacteria Pseudomonas sp. 418 with loss of the ability to colonize roots

Mutants of nitrogen-fixing rhizospheric bacterium Pseudomonas sp. 418, which lacked the competitive ability to colonize roots, were induced by random Tn5 mutagenesis. By means of Southern blot analysis, it was shown that single transposon insertions occurred in eight mutants, whereas in two mutants, the Tn5 insertion occurred twice in different DNA regions. Analysis of these mutants revealed the following disturbances of characters having adaptive significance: weakened attachment to the root surface; a defect in chemotaxis; impaired motility as a result of the loss of flagella or nondisjunction of cells after division; and alterations in the synthesis of exopolysaccharides. The effect of Tn5 insertions was, as a rule, pleiotropic, which suggests the coordinated expression of traits essential for the survival of bacterial cells in the root region.     

Polymorphism of SSR alleles in pear cultivars grown in Belarus

Using SSR markers designed for Malus × domestica Borkh. genetic polymorphism of 43 pear accessions cultivated in Belarus was examined. A total of 217 alleles were identified with the mean number of 12.8 alleles per marker. The mean PIC value was 0.81; the mean number of informative alleles, 6.49. The heterozygosity level ranged from 0.30 to 0.84. Genetic diversity of SSR alleles in pear and apple genomes was compared. A method of identification of commercial pear cultivars using a set of six SSR markers was suggested.     

Experimental non-culturable Vibrio cholerae eltor and its biological properties

In experiments with the cultivation of V. cholerae eltor under the conditions of high salt concentration, as well as low temperature and deficiency in nutrient substances, uncultivable forms (UF) of toxigenic and nontoxigenic vibrios were obtained. The absence of growth of seeded vibrios after the filtration of samples (with a filter of 0.22 micron), the preservation of specific antigenic determinants and the initial set of genes, changes in the morphology of cells (small size, coccoid form with the flagella retained) confirm the transition of V. cholerae eltor under study into the uncultivable state which, under unfavorable conditions, more rapidly develops in toxigenic vibrios than in nontoxigenic ones. The analysis of the INT-reductase activity of UF disintegrates revealed that they had endogenic respiration whose activity increased (4.5- to 6.5-fold) in the presence of the exogenic intermediates of the Krebs cycle. The uncultivable forms of the vibrios retain genes responsible for pathogenicity, as well as their antigenic determinants.     

Cholera in the Far East of Russia. Communication 1. Epidemiological characteristics of the outbreak of cholera El tor in Vladivostok

The materials on the investigation of the outbreak cholera eltor in Vladivostok, caused by the import of infection from China. The leading role of the water route of transmission of this infection is shown due to the contamination of water sources with non-decontaminated sewage water. The complex of antiepidemic measures was carried out, which made it possible to arrest the spread of cholera and liquidate its foci.     

Identification of leaf rust resistance genes in wheat (Triticum aestivum L.) cultivars using molecular markers

A collection of 68 cultivars of common wheat has been screened for leaf rust resistance genes with the use of molecular markers. Markers of genes Lr1, Lr9, Lr10, Lr19, Lr20, Lr21, Lr24, and Lr26 have been used. It has been suggested that allele Xgwm295 be used as a marker for identifying the Lr34 gene. The genes originating from Triticum aestivum L., as well as the Lr26 gene contained in rye translocation 1RS, are the most frequent. Genes originating from wild wheats were rarer in the cultivars studied.     

Spatial and genetic structure of a Melittis sarmatica Klok. (Lamiaceae) metapopulation located in the Volkovysk Upland (Belarus)

The spatial and genetic structure of the metapopulation of Melittis sarmatica Klok. from the Volkovysk Upland (Grodno region, Belarus) has been studied. The use of the RAPD method for genetic analysis of the similarity of populations revealed the exchange of genetic information between metapopulation components. We also revealed the most stable connections within the metapopulation, the key and problem elements of its structure, and some genetically separate groups. A negative linear dependence between the level of genetic similarity of populations and the distance between them was observed.