[Experimental study of mixed infection by Vibrio cholerae and Salmonella typhi]. / Izuchenie smeshannoi infektsii, vyzyvaemoi Vibrio cholerae i Salmonella typhi, v éksperimente.

Mixed infection caused by V.cholerae and S.typhi was studied on guinea pig gall-bladder, used as an experimental model. These microorganisms coexisted in association in animals and exhibited no pronounced antagonistic properties in vitro. The cultures isolated from the organs of infected guinea pigs did not differ from initial ones. The study revealed that in nutrient broth containing 50% of dried bile salmonellae were preserved, but not V.cholerae. The latter could co-exist with S.typhi in 1% biliary medium prepared on meat-peptone broth (MPB). The use of bile and MPB as the basis for media intended for the study of material obtained from cholera and typhoid fever patients is recommended.

[The reasons for the resistance of Vibrio cholerae to diagnostic phages]. / Prichiny ustoichivosti kholernykh vibrionov k diagnosticheskim fagam.

Phage resistance of 225 strains of cholera germs of O1 group obtained from different countries in 1988-1992 has been analyzed. Change of sensitivity to diagnostic phages was mostly connected with the decrease or loss of agglutinability in cholera sera. Phage resistance is rather conditioned by the change of the surface structures of the cell and by further change of phage reception zones. The increase in the number of strains sensitive to diagnostic phages after 6-12 months of storage evidenced for stabilization of cell wall structures and increase of their viability under relatively favourable conditions of storage.

[Isolation and characterization of new nuclear srm gene mutation causing coordinated changes in the maintenance of nuclear and mitochondrial genetic structures in the yeast Saccharomyces]. / Poluchenie i kharakteristiki novykh iadernykh gennykh mutatsii srm, vyzyvaiushchikh koordinirovannye izmeneniia podderzhaniia iadernykh i mitokhondrial'nykh geneticheskikh struktur u drozhzhei sakharomitsetov.

From grown cultures of UV-irradiated Saccharomyces cerevisiae cells with disomy at chromosome IV, clones with nuclear gene mutations were isolated, each of which was suggested to change both mitochondrial spontaneous rho- mutability and the mitotic stability of extra natural chromosomes. Four such nonallelic mutations (srm8, srm12, srm15, and srm17) were isolated, and their phenotypic expression characterized. All four mutations are associated with decreased spontaneous rho- mutability and virtually block sporulation in homozygous mutant diploids. Mutation srm8 is temperature-sensitive and, most probably, involves an essential gene. Double mutants of genotypes srm8 cdc28-srm and srm8 srm12 are nonviable. Mutation srm12 increases the rate of spontaneous loss of extra chromosome XIV by disomics by a factor of about 30. Mutation srm15 induces a small (about twofold) but statistically significant decrease of this rate. Mutations srm8 and srm17 drastically decelerate reproduction of cells with disomy, which prevents quantitative estimations of rates of loss of extra chromosomes.