Contribution of determinants, located in Bacillus anthracis chromosomes, in realizing the pathogenic properties of the pathogen

Comparative study of virulence of B. anthracis strains harbouring pXO1 and pXO2 plasmids in mice and guinea pigs showed that among six B. anthracis strains, three were 100-1000 times less virulent for guinea pigs. Genetic construction of B. anthracis strains using transduction and conjugation transfer of resident plasmids permitted us to rule out the effects of modified pXO1 and pXO2 replicons and to prove the existence of nonidentified chromosome locuses responsible for the development of an infectious process in anthrax, along with plasmid determinants of virulence.     

The activity of xylose reductase and xylitol dehydrogenase in yeasts

The activity and the cofactor specificity of xylose reductase and xylitol dehydrogenase were studied in extracts of yeasts from the genera Candida, Kluyveromyces, Pachysolen, Pichia, and Torulopsis grown under microaerobic conditions. It was found that xylitol dehydrogenase in all of the yeast species studied is specific for NAD+; xylose reductase in the xylitol-producing species C. didensiae, C. intermediae, C. parapsilosis, C. silvanorum, C. tropicalis, Kl. fragilis, Kl. marxianus, P. guillermondii, and T. molishiama is specific for NADPH; and xylose reductase in the ethanol-producing species P. stipitis, C. shehatae, and Pa. tannophilus is specific for both NADPH and NADH.     

Hybrid formation and copulation activity in the yeast Pachysolen tannophilus

The copulation activity and hybrid formation efficiency have been studied in the xylose-assimilating yeast Pachysolen tannophilus. It was shown that the presence of 2% D-glucose, 0.5% yeast extract, and 2% agarose in the growth medium provided for the highest frequencies of hybrid formation. Atypical hybrid cultures similar in morphophysiological characteristics to native haploid strains of P. tannophilus were revealed in the course of hybridization. The genesis mechanism of such cultures and the reasons for the restricted applicability of hybridological analysis to genetic studies of P. tannophilus are discussed.     

The Activity of Key Enzymes in Xylose-Assimilating Yeasts at Different Rates of Oxygen Transfer to the Fermentation Medium

The activities of xylitol dehydrogenase and xylose reductase in the yeasts Candida shehatae, C. didensiae, C. intermediae, C. tropicalis, Kluyveromyces marxianus, Pichia stipitis, P. guillermondii, Pachysolen tannophilus, and Torulopsis molishiama were studied at different oxygen transfer rates (OTRs) to the fermentation medium (0, 5, and 140 mmol O₂/(l h)). The activities of these enzymes were maximum in the yeasts P. stipitis and C. shehatae. The xylitol dehydrogenase of all the yeasts was NAD⁺-dependent, irrespective of the intensity of aeration. The xylose reductase of the yeasts C. didensiae, C. intermediae, C. tropicalis, Kl. marxianus, P. guillermondii, and T. molishiama was NADPH-dependent, whereas the xylose reductase of P. stipitis, C. shehatae, and Pa. tannophilus was specific for both NADPH and NADH. The effect of OTR on the activities of the different forms of xylitol dehydrogenase and xylose reductase in xylose-assimilating yeasts is discussed.     

Specific Features of Fermentation of D-Xylose and D-Glucose by Xylose-Assimilating Yeasts

The ability to assimilate D-glucose and D-xylose was studied in 21 yeast species of the following genera: Candida, Kluyveromyces, Pachysolen, Pichia, and Torulopsis. All the cultures fermented D-glucose with the formation of ethanol. During the assimilation of D-xylose, ethanol was produced by P. stipitis and C. shehatae, whereas xylitol was produced by C. didensiae, C. intermediae, C. parapsilosis, C. silvanorum, C. tropicalis, K. fragilis, K. marxianus, P. guillermondii, and T. molishiama. The yeast P. tannophilus produced comparable amounts of both alcohols. The possible use of xylose-assimilating yeasts for the production of xy-litol and ethanol is discussed.     

Functional computed tomography in the diagnosis of injuries to the ligamentous apparatus of the upper cervical spine in children and adolescents]

Altogether 40 children and adolescents were investigated after injuries of the upper cervical spine using radiograms through the open mouth, functional radiograms of the cervical spine, and functional CT. Various injuries of the ligamentous apparatus of the upper cervical spine were revealed in 31 patients.     

study of the virulence of a recombinant strain of Bacillus anthracis, obtained as a result of transductive transfer of chromosomal genes from a strain of Bacillus cereus

Auxotrophic markers of B. anthracis strains differing them from other Bacillus representatives have been determined. Chromosome genes from prototrophic B. cereus strain were transduced into auxotrophic B. anthracis strain. The properties of transductants were studied in order to establish common transfer of chromosomal determinants responsible for realization of various signs. Transduction mating between species resulted in construction of prototroph B. anthracis strains (pX01- pX02+), whose derivatives are characterized by decreased virulence for laboratory animals.     

Peculiarities of hybrid formation and copulation activity in the yeast <Emphasis Type="Italic">Pachysolen tannophilus</Emphasis>

The copulation activity and hybrid formation efficiency have been studied in the xylose-assimilating yeast Pachysolen tannophilus. It was shown that the presence of 2% D-glucose, 0.5% yeast extract, and 2% agarose in the growth medium provided for the highest frequencies of hybrid formation. Atypical hybrid cultures similar in morphophysiological characteristics to native haploid strains of P. tannophilus were revealed in the course of hybridization. The genesis mechanism of such culture and the reasons for the restricted applicability of hybridological analysis to genetic studies of P. tannophilus are discussed.     

Conditions favoring differentiation and stabilization of the life cycle of the yeast Pachysolen tannophilus

Conditions favoring differentiation and stabilization of the life cycle of the yeast Pachysolen tannophilus have been studied. When concentrations of the carbon source in the medium were lower than 100 g/l, it was found to be favorable to the mating of vegetative cells, both haploid and diploid. The addition of nitrogen and sulfur sources to the medium influenced the life phases of haploid cells and partially stabilized the vegetative growth of diploid cells. Enrichment of the nutrient medium with potassium, vitamins, and microelements was shown to be necessary for the formation and maturation of conjugated ascospores. Microelements, vitamins, and phosphorus in excessive amounts activated conjugation but did not provide for the distinct phases of formation of unconjugated asci and spores in the diploid cells. Possible reasons for the unstable diplophase in the yeast P. tannophilus are discussed.