[The physicochemical characteristics of ribosomal fractions from Pseudomonas aeruginosa obtained by precipitation with polyethylene glycol 6000]. / Fiziko-khimicheskaia kharakteristika ribosomal'nykh fraktsii iz Pseudomonas aeruginosa, poluchennykh osazhdeniem poliétilenglikolem 6000.

Ribosomal fractions containing up to 72% of ribosomal material and 25% of sugars (among them, about 6% of hexose) were isolated from P.aeruginosa cells, immunotypes F-1, 2, 6 and 7, by precipitation with polyethylene glycol 6000. Lipopolysaccharide, determined in the test for ketodesoxyoctanoic acid, was not detected in these fractions, but, as determined in the passive hemagglutination test, the content of O-antigen in the preparations was 3-25%. O-antigen and ribosome present in the fractions formed a complex, disintegrating after treatment with trilon B.

[The immunogenic and serological properties of the O-specific polysaccharide (L-hapten) in Shigella]. / Immunogennye i serologicheskie svoistva O-spetsificheskogo polisakharida (L-gaptena) shigell.

O-specific polysaccharide (L-hapten) was isolated earlier (Zh. mikrobiol. epidemiol. immunobiol., 1989, No. 11, pp. 8-11). In this paper L-hapten was shown to be unable, even at high concentrations (up to 2,000 micrograms/ml), to sensitize sheep red blood cells for passive hemagglutination by O-antibodies. At the same time classical LPS and heat-activated LPS were active at concentrations ot 32 and 8 micrograms/ml respectively. The O-antibody-neutralizing activity of L-hapten was lower than that of LPS 10(3)-10(4) times in the passive hemagglutination test and 25-50 times in competitive ELISA. The immunogenicity of isolated L-hapten was very weak: primary response in mice to the i.v. injection of 1-10 micrograms of L-hapten was similar to the effect produced by 10(-3)-10(-4) micrograms of LPS. No protective activity of L-hapten was noted in mice when the challenge dose of virulent shigellae was 16 LD50 or more, and only a weak protective effect was observed with a low challenge dose (8 LD50). The molecular basis of low serological and biological activity of L-hapten is discussed. The most probable explanation of the results obtained in this study is that L-hapten contains some nonspecific carbohydrates, inserted in or complexed with the O-side chain. Despite its low immunogenicity, L-hapten can be an important component of effective bacterial vaccines provided it is included into a suitable delivery system as is the case with Shigella ribosomal vaccine.

[O-specific L-hapten in the composition of Shigella sonnei]. / O-spetsificheskii L-gapten v sostave Shigella sonnei.

Along with classical lipopolysaccharide (LPS), O-specific material not precipitated by ultracentrifugation has been isolated from the water-phenol extract of S. sonnei avirulent strain 9090 possessing complete antigenic properties. The purification of O-antigen contained in the supernatant fluid has been carried out by the gel filtration of the fluid, previously treated with ribonuclease, in a column packed with Sephadex G-100. The polysaccharide nature of O-antigen thus obtained, the absence of lipid A and KDO and the low content of hexoses, or core-specific saccharides of S. sonnei LPS, in this antigen make it possible to classify this material with O-components of microbial cells, described by different authors as "native protoplasmic polysaccharide" or "L-hapten" and formed by polymers of LPS O-side chains. The content of this component in S. sonnei strains under study is, on the average, 2.5% of the weight of dry microbial substance. L-hapten preparations obtained in the course of our investigations have been found to contain two O-specific antigens detected by immunoelectrophoresis and immunodiffusion, as well as by sedimentation in saccharose gradient, where they form peaks corresponding to 4.3 S and 10.8 S. This polysaccharide O-antigen is supposed to be capable of interaction with ribosomal particles and suitable for use as a component of ribosomal dysentery vaccines.

[Study of the adaptation resistance in bacteria to membrane active polypeptide antibiotics]. / Izuchenie adaptatsionnoi ustoichivosti bakterii i membranoaktivnym polipeptidnym antibiotikam.

Variants of Micrococcus lysodeikticus resistant to 100 micrograms/ml of gramicidin S with preserved resistance in subcultures on media without the antibiotic were isolated as a result of prolonged adaptation on a solid medium with increasing concentrations of gramicidin. The sensitive and resistant cells did not differ by their ability to bind gramicidin. Under the antibiotic effect permeability of the cytoplasmic membranes of the intact cells in the sensitive bacteria appeared to be impaired to a greater extent than that of the membranes of the cells in the resistant variant. Comparison of the lytic activity of gramicidin and its derivatives with respect to the protoplasts prepared with the cells of the initial and resistant variants of M. lysodeikticus revealed much higher resistance of the resistant variant protoplasts to the membrane-disorganizing effect of the preparations. Malate dehydrogenase and NADH-oxidase in the membrane preparations of the resistant variant cells differed from analogous enzymes from the membranes of the initial strain by the levels of their activity and sensitivity to gramicidin. It is likely that during adaptation of M. lysodeikticus to gramicidin significant changes in the cell cytoplasmic membranes occurred.

[Effect of salts on the lytic activity of gramicidin S and its derivatives]. / Vliianie solei na liticheskuiu aktivnost' gramitsidina S i ego proizvodnykh.

Potassium and sodium chlorides, sulfates, acetates and phosphates activated the lytic action of gramicidin S and its derivatives on protoplasts of M. lysodeikticus. The derivatives used were positively charged and neutral by the free amino groups in the ornithine moieties. The salts had no effect on lysis of the bacillar protoplasts by gramicidin S and its positively charged derivatives. The lytic effect of the neutral derivative on the bacillar protoplasts markedly increased in the presence of the salts, activation of the lysis by the phosphates being more pronounced than that by the other salts. Increased membrane activity of gramicidin S in the presence of the salts was not connected with association of the substance molecules in solution. Probably it was due to increased destruction of the membranes at the account of activated detergent effect of the antibiotic and its derivatives.

[Action of different types of gramicidin S derivatives on bacterial cells and protoplasts]. / Deistvie razlichnykh tipov proizvodnykh gramitsidina S na kletki i protoplasty bakterii.

The work was concerned with studying the effect of gramicidin S derivatives with modified free amino groups of ornithine residues on bacterial cells and protoplasts. The substitution of the amino groups with neutral or carboxyl-containing groups eliminated or sharply decreased the antibacterial activity of gramicidin S, its binding to the cells, and the ability to change the permeability of the cytoplasmic membranes of the intact cells. However, the neutral derivatives and the derivative with acidic properties showed a considerable lytic activity when they were incubated with the protoplasts of Micrococcus lysodeikticus, Bacillus megaterium and Bacillus subtilis. Hence, these compounds preserved a certain membranotropic level. Those gramicidin S derivatives with modified ornithine amino groups which possessed basic properties were similar to gramicidin S in the antibiotic activity, the modified permeability of the membranes, the ability to bind with the cells, and the lytic action on the protoplasts.