Production and characterization of strain-specific monoclonal antibodies against outer membrane components of Azospirillum brasilense Sp245

Assessment of the structural and functional diversities of plant microbiota: Achievements and challenges - A review

Analyses of the spatial localization and the functions of bacteria in host plant habitats through in situ identification by immunological and molecular genetic techniques combined with high resolving microscopic tools and 3D-image analysis contributed substantially to a better understanding of the functional interplay of the microbiota in plants. Among the molecular genetic methods, 16S-rRNA genes were of central importance to reconstruct the phylogeny of newly isolated bacteria and to localize them in situ. However, they usually do not allow resolution for phylogenetic affiliations below genus level. Especially, the separation of opportunistic human pathogens from plant beneficial strains, currently allocated to the same species, needs genome-based resolving techniques. Whole bacterial genome sequences allow to discriminate phylogenetically closely related strains. In addition, complete genome sequences enable strain-specific monitoring for biotechnologically relevant strains. In this mini-review we present high resolving approaches for analysis of the composition and key functions of plant microbiota, focusing on interactions of diazotrophic plant growth promoting bacteria, like Azospirillum brasilense, with non-legume host plants. Combining high resolving microscopic analyses with specific immunological detection methods and molecular genetic tools, including especially transcriptome analyses of both the bacterial and plant partners, enables new insights into key traits of beneficial bacteria-plant interactions in holobiontic systems.

Quantification of natural populations of Gluconacetobacter diazotrophicus and Herbaspirillum spp. In sugar cane (Saccharum spp.) Using differente polyclonal antibodies

The species Gluconacetobacterdiazotrophicus, Herbaspirillum seropedicae and H. rubrisubalbicans are endophytic N₂-fixing [diazotrophic] bacteria which colonise not only roots, but also the aerial tissue of sugar cane. However, the technique most commonly used to quantify the populations of these microbes in plants is by culturing serial dilutions of macerates of plant tissues in N free semi-solid media which are only semi-selective for the species/genera [the Most Probable Number (MPN) Technique] and each culture must be further subjected to several tests to identify the isolates at the species level. The use of species-specific polyclonal antibodies with the indirect ELISA (enzyme-linked immunosorbent assay) can be an alternative which is rapid and specific to quantify these populations of bacteria. This study was performed to investigate the viability of adapting the indirect ELISA technique to quantify individually the populations of these three species of diazotroph within the root and shoot tissues of sugarcane. The results showed that species-specific polyclonal antibodies could be obtained by purifying sera in protein-A columns which removed non-specific immuno-globulins. It was possible to quantify the three bacterial species in the Brazilian sugarcane variety SP 70-1143 in numbers above 10⁵ cells per g fresh weight in roots, rhizomes and leaves. The numbers of the different bacterial species evaluated using the ELISA technique were found to be higher than when the same populations were evaluated using the MPN technique, reaching 1400 times greater for G. diazotrophicus and 225 times greater for Herbaspirillum spp. These results constitute the first quantification of Herbaspirillum using immunological techniques.

Structure of the O-polysaccharide from the Azospirillum lipoferum Sp59b lipopolysaccharide

A neutral O-specific polysaccharide was obtained by mild acid hydrolysis of the lipopolysaccharide of the plant-growth-promoting bacterium Azospirillum lipoferum Sp59b. On the basis of sugar and methylation analyses along with 1D and 2D (1)H and (13)C NMR spectroscopy, including a NOESY experiment, the following structure of the branched hexasaccharide repeating unit of the O-polysaccharide was established: [carbohydrate structure: see text].

Characterization and application of a strain-specific monoclonal antibody against the rhizosphere bacterium Azospirillum brasilense Wa5

A hybridoma cell line producing a rat monoclonal antibody (MAb Bo-33) directed against lipopolysaccharide of Azospirillum brasilense Wa5 has been established and characterized. Whole bacteria were used as immunogens. The number of antigens per cell was about 1500. The number of antigens per cell of reisolates from the rhizosphere of what was similar to the number of antigens of bacteria cultivated in rich medium. The sensitivity of detection using MAb Bo-33 was about 100 bacteria/ml. Therefore, the MAb was suitable for in situ immunofluorescence detection and a sensitive direct quantification of Azospirillum brasilense Wa5 in rhizosphere extracts.