Functioning of plant-bacterial associations under osmotic stress in vitro

World Journal of Microbiology and Biotechnology - Derived from RNA, 5?-ribonucleotides, especially Inosine-5?-monophosphate (IMP) and guanosine-5?-monophosphate (GMP), can enhance...     

Electrooptical properties of the microbial suspensions during a cell’s interaction with the antibodies of a different specificity

The electrooptical abilities of the microbial suspensions during a cells interaction with antibodies (ABs) of a different specificity have been studied on the example of the Azospirillum brasilense Sp245 cells and their interaction with the polyclonal monospecific and polyspecific antibodies. Measuring of the orientational spectra of the cells has been performed using the ELUS electrooptical analyzer. A discrete frequency set of an orienting electric field (740, 1000, 1450, 2000, and 2800 kHz) was used. It has been shown that an interaction of the polyspecific AB with the investigated cells redoubles the value of an electrooptical signal of the cells’ suspension as compared with the monospecific antibodies. These findings can be used for a development a new method of microorganism detection.     

Electrophysical characteristics of Azospirillum brasilense Sp245 during interaction with antibodies to various cell surface epitopes

This work was undertaken to examine the electrooptical characteristics of cells of Azospirillum brasilense Sp245 during their interaction with antibodies developed to various cell surface epitopes. We used the dependences of the cell suspension optical density changes induced by electroorientation on the orienting field frequency (740, 1000, 1450, 2000, and 2800kHz). Cell interactions with homologous strain-specific antibodies to the A. brasilense Sp245 O antigen and with homologous antibodies to whole bacterial cells brought about considerable changes in the electrooptical properties of the bacterial suspension. When genus-specific antibodies to the flagellin of the Azospirillum sheathed flagellum and antibodies to the serologically distinct O antigen of A. brasilense Sp7 were included in the A. brasilense Sp245 suspension, the changes caused in the electrooptical signal were slight and had values close to those for the above changes. These findings agree well with the immunochemical characteristics of the Azospirillum O antigens and with the data on the topographical distribution of the Azospirillum major cell surface antigens. The obtained results can serve as a basis for the development of a rapid test for the intraspecies detection of microorganisms.     

On the role of carbohydrate-protein highly selective interactions in the biological activity of glycoconjugates: <Emphasis Type="Italic">Grifola frondosa</Emphasis> (Fr.) S.F. Gray lectin binding to specific and non-specific antibodies

Both quantitative and qualitative estimations of the basidiomycete Grifola frondosa lectin binding to the specific and non-specific polyclonal rabbit antibodies were attempted. The lectin complexation with homological antibodies was shown to be characterized by greater binding constants as compared to non-homological antibodies. Therewith the values of changes in standard free energy ∆G ⁰ displaying a strength of both complexes were essentially the same. The data obtained testify to universality of biospecific reactions “antigen–antibody” and “lectin–carbohydrate” at a molecular level, and could give new insight into the phenomenon of these biospecific interactions. The actual specificity in the above bio-recognition processes could differ from the results of in vitro assays using lectins, and, therefore, should be interpreted carefully when concluding on the lectins behaviour in living systems.     

Chemical composition and immunochemical characteristics of the lipopolysaccharide of nitrogen-fixing rhizobacterium Azospirillum brasilense CD

The chemical composition of the lipopolysaccharide of the associative diazotrophic rhizobacterium Azospirillum brasilense Cd has been studied. Among the main components of the hydrophobic part of the lipopolysaccharide, we identified 3-hydroxytetradecanoic, hexadecenoic, 3-hydroxyhexadecanoic, hexadecanoic, octadecenoic, and nanodecanoic fatty acids; the carbohydrate part contained rhamnose, galactose, and mannose. Polyclonal antibodies against the preparation under study were raised in rabbits. Serological relations between A. brasilense Cd and other strains of Azospirillum spp. were studied using double radial immunodiffusion and enzyme-linked immunosorbent assay.     

Effect of bacterial lipopolysaccharides on morphogenetic activity in wheat somatic calluses

We evaluated the effect of lipopolysaccharides from the plant-growth-promoting associative bacterium Azospirillum brasilense Sp245 and from the enteric bacterium Escherichia coli K12 on the morphogenic potential of in vitro-growing somatic calluses of soft spring wheat (Triticum aestivum L. cv. Saratovskaya 29). A genetic model was used that included two near-isogenic lines of T. aestivum L. cv. Saratovskaya 29 with different embryogenic capacities; one of these lines carries the Rht-B1 dwarfing gene, whereas the other lacks it. When added to the nutrient medium, the lipopolysaccharide of A. brasilense Sp245 promoted the formation of calluses with meristematic centers and stimulated the regeneration ability of the cultured tissues in both lines. By contrast, the lipopolysaccharide of the enteric bacterium E. coli K12 barely affected the morphogenetic activity of callus cells and the yield of morphogenic calluses and regenerated plants. These findings indicate that the lipopolysaccharide of the plant-growth-promoting associative bacterium A. brasilense Sp245 specifically enhances the morphogenetic activity of wheat somatic tissues, which increases the efficacy of culturing of genotypes with a relatively low morphogenic potential. The results of the study may contribute to the improvement of the efficacy of plant cell selection and gene engineering and to a better understanding of the mechanisms responsible for plant recognition of lipopolysaccharides of associative bacteria.     

Composition and immunochemical characteristics of exopolysaccharides from the rhizobacterium <Emphasis Type="Italic">Paenibacillus polymyxa</Emphasis> 1465

Exopolysaccharides (EPS) synthesized by Paenibacillus polymyxa 1465 in the course of batch cultivation were proven to contain neutral and acidic fractions. EPS are heterogeneous polysaccharides, represented by a complex of macromolecules with molecular mass of 7 × 10⁴ to 2 × 10⁶ Da. The acidic component was shown to be predominant in EPS preparations isolated from bacteria cultivated on glucose, which corresponds to a higher viscosity of EPS water solutions. The exoglycans were shown to contain glucose, mannose, galactose, and uronic acids. Polyclonal rabbit antibodies against the isolated P. polymyxa 1465 EPS preparations were used in a comparative immunodiffusion analysis of a number of P. polymyxa strains.     

A method for studying insoluble immune complexes

Two variants of a method for determining the average composition of insoluble immune complex particles (IICP) are described. The first variant is based on measuring the specific turbidity (the turbidity per unit mass concentration of the dispersed substance) and the average size of IICP determined from dynamic light scattering (DLS). In the second variant, the slope of the logarithmic turbidity spectrum (wavelength exponent) is used instead of DLS particle size. Both variants allow the average biopolymer volume fraction to be determined in terms of the average refractive index of IICP. The method is exemplified by two experimental antigen+antibody systems: (i) lipopolysaccharide-protein complex (LPPC) of Azospirillum brasilense Sp245+rabbit anti-LPPC; and (ii) human IgG (hIgG)+sheep anti-hIgG. We have found that IICP can be modeled by incompact porous particles that contain about 30% of biopolymer substance and 70% of buffer.     

Capsular polysaccharide of the bacterium <Emphasis Type="Italic">Azospirillum lipoferum</Emphasis> Sp59b: Structure and antigenic specificity

Antigenic differences were revealed between the cell wall outer membrane lipopolysaccharides and the capsular high molecular weight bioglycans for a typical strain of the nitrogen-fixing rhizobacterium Azospirillum lipoferum Sp59b using antibodies prepared against the homologous lipopolysaccharide and lipopolysaccharide-protein complex. From the capsular lipopolysaccharide-protein and polysaccharide-lipid complexes of A. lipoferum Sp59b, polysaccharides were isolated and their structure was for the first time established in Azospirillum by monosaccharide analysis which included determination of the absolute configurations, methylation, O-deacetylation, and one- and two-dimensional NMR spectroscopy. The polysaccharides of the capsular complexes were shown to have identical structure of the branched tetrasaccharide repeating unit, which differs from the structure of the O-specific polysaccharide within the outer membrane lipopolysaccharide of this strain.     

Detection of a sheath on <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> polar flagellum

The presence of a polysaccharide sheath on the surface of the polar flagellum of Azospirillum brasilense was revelted by immunoelectron microscopy and immunodiffusion analysis with strain-specific antibodies to lipopolysaccharides (LPS). The antigenic identity of A. brasilense Sp245 sheath material and one of the two O-specific polysaccharides of its somatic LPS was demonstrated. The screening effect of the sheath in respect to flagellin was determined by agglutination tests and by the inhibition of azospirilla motility in liquid and semisolid agarized media caused by strain-specific antibodies to LPS; no pronounced effect of genus-specific antibodies to flagellin was observed.