Pleiotropic effects of the lpxM mutation in Yersinia pestis resulting in modification of the biosynthesis of major immunoreactive antigens.

Deletion mutants in the lpxM gene in two Yersinia pestis strains, the live Russian vaccine strain EV NIIEG and a fully virulent strain, 231, synthesise a less toxic penta-acylated lipopolysaccharide (LPS). Analysis of these mutants revealed they possessed marked reductions in expression and immunoreactivity of numerous major proteins and carbohydrate antigens, including F1, Pla, Ymt, V antigen, LPS, and ECA. Moreover, both mutants demonstrated altered epitope specificities of the antigens as determined in immunodot-ELISAs and immunoblotting analyses using a panel of monoclonal antibodies. The strains also differed in their susceptibility to the diagnostic plague bacteriophage L-413C. These findings indicate that the effects of the lpxM mutation on reduced virulence and enhanced immunity of the Y. pestis EV DeltalpxM is also associated with these pleiotropic changes and not just to changes in the lipid A acylation.

[Study of ability to form biofilms in main and non-main subspecies of Yersinia pestis strains].

AIM: To compare biofilm formation in main and non-main subspecies of Yersinia pestis strains as well as in Yersinia pseudotuberculosis strains and to study influence of different genes on expression of this characteristic in different subspecies of Y. pestis. MATERIALS AND METHODS: Study of biofilm formation was performed bygrowing cultures on LB broth in polystyrene Petri dishes with subsequent staining of biofilms formed on the dishes' bottom with crystal violet as well as by electron microscopy. Pigment-sorption sign was detected on differential medium with Congo red. RESULTS: It was shown that the majority of Y. pestis strains and all strains of Y. pseudotuberculosis form well-expressed biofilms on abiotic surface. Formation of biofilms by Y. pestis strains is clearly correlateswith their ability to form pigmented colonies on solid medium with dyestuff. Genes which according to literature data are necessary for biofilm formation by Y. pestis and Y. pseudotuberculosis were found in genome of non-main species. CONCLUSION: Ability of Y. pestis strains belonging to main and non-main subspecies to form biofilm on abiotic surface was revealed.

[Molecular mechanisms of the plague pathogenic agent interaction with invertebrates].

Microbe Russian Anti-Plague Research Institute, Saratov, Russia The literature data and experimental results of the authors on the molecular basis of plague agent interaction with invertebrates are discussed. The details of the plague agent life cycle, its genome organization, and molecular genetic mechanisms of its survival in flea vector and on the nematode cuticule are discussed. The experimental data about the ability to form biofilms at abiotic and biotic surfaces in the Yersinia pestis strains of the main and non-main subspecies are presented. Mechanisms of horizontal and vertical transmission of plague agent are considered. The suggestion about participation of the new member in the complex parasitic biocenosis (nematode, vector parasite) is put forward.

[Vibrio cholerae temperate phage O139: characteristics and role in changing expression of chromosomal virulence genes]. / Umerennyi fag Vibrio cholerae O139: kharakteristika i rol' v izmenenii ékspressii khromosomnykh genov virulentnosti.

Restriction analysis of temperate cholera phage 139 isolated from Vibrio cholerae P16064, serogroup 0139, showed its DNA to be double-stranded linear with cohesive terminals. DNA-DNA hybridization on nylon membranes revealed that many V. cholerae strains of serogroup 0139 isolated in different regions contained a temperate cholera phage 139 in their genomes. Southern blot hybridization of chromosomal DNA PST-fragments with phage probe showed that the temperate phage 139 was identical to the temperate phage of serogroup II V. eltor. The phage integrated in the chromosome near genes encoding motility (mot) and production of the capsule (cap) and purine (pur). Phage genome is apparently responsible for instability of cap, pur, and mot genes whose products are important for the development of an infectious process in cholera.

[The variability of Yersinia pestis in the body of the flea]. / Izmenchivost' Yersinia pestis v organizme blokhi.

Changes in the morphology and ultrastructure of Y.pestis cells at different periods of their stay in the body of fleas (Citellophilus tesquorum altaicus) have been studied. The study, carried out by means of optical and electron microscopy, as well as with the use of a culture medium for the isolation of L-forms, has revealed that in the body of fleas Y.pestis cells undergo the effect of processes leading to their L-transformation. As the result of L-transformation, the infective agent may take altered forms, including L-like variants. Such forms are retained in hungry insects and are capable of prolonged survival in the body of the carrier.

[Pathogenic action of the plague microbe on the flea Xenopsylla cheopis and the ultrastructure of the causative agent at various times of its stay in the vector]. / Patogennoe deistvie chumnogo mikroba na organizm blokhi Xenopsylla cheopis i ul'trastruktura vozbuditelia v razlichnye sroki prebyvaniia v perenoschike.

Pathology of gastro-intestinal tract of Xenopsylla cheopis fleas infected with plague microbe was determined by means of electron microscopy. Ultrastructure of plague microbe during different periods of its stay in the vector was studied.

[Detection and characterization of the plasmids of the plague microbe which determine the synthesis of pesticin I, fraction I antigen and "mouse" toxin exotoxin]. / Vyiavlenie i kharakteristika plazmid chumnogo mikroba, determiniruiushchikh sintez pestitsina I, antigena fraktsiia I i ékzotoksina "myshinogo" toksina.

Plasmid DNA was isolated from Yersinia pestis strains containing pesticin I or fraction I antigen and "mouse" toxin determinants. Specificity of DNA preparations was studied by using them for transformation of plague agent strains carrying no plasmids. pPstI plasmid (molecular weight 7,0-7,8 MD) encoded pesticin I, fibrinolysin and plasmacoagulase synthesis. Fraction I antigen and "mouse" toxin production determinants were borne on pFraI/Tox plasmid (molecular weight about 50 MD). The observation that some Y. pestis cultures, having lost the ability to synthesize one of pFraI/Tox products, still retained this plasmid in their cells, is regarded as an evidence for a complicated regulation of pFraI/Tox function.

[The proventriculus of the Xenopsylla cheopis flea studied by scanning electron microscopy]. / Izuchenie predzheludka blokhi Xenopsylla cheopis v skaniruiushchem élektronnom mikroskope.

The proventriculus of the flea X. cheopis was studied by means of scanning electron microscopy. The external surface of the proventriculus is a rigid structure with an alveolate surface ("wasp nest") formed by muscular cords. The internal surface of the proventriculus is represented by numerous acanthae which fall close together. They have a shape of bent dens with longitudinal sharply angular edges and concave spaces between them. Some edges are crenate.

[Fertility and the crossing system in Vibrio cholerae]. / Fertil'nost' i sistema skreshchivaniia u kholernogo vibriona.

A system of crossing of 2 biotypes of cholera strains and nonagglutinating vibrios was worked out by means of modified Parker and Romig's method. The most frequent inheritance of the sex factor was noted in conjugation of strains belonging to the classic biotype. Inheritance of chromosomal genes (pur) was less incident. Sex pili 9 to 10 nm in diameter were revealed in donor V. cholerae 569 (B) P+ strain.

[Electron microscopic study of dry live plague vaccine EB by the scanning method]. / Elektronno-mikroskopicheskoe issledovanie chumnoi zhivoi sukhoi vaktsiny EB metodom skanirovaniia

Dry live plague vaccine EB was examined under microscope; it appeared that in the mentioned preparation the bacterial cells were enclosed in the artificial sucrose-gelatin capsule of the stabilizer which apparently maintained the vital activity of the microorganisms in the state of anabiosis by forming a stable bond with the bacterial body.