[Effect of Congo red on the motility of the bacterium Azospirillum brasilense].

In semiliquid laboratory media, the bacterium Azospirillum brasilense migrates with the formation of swarming rings. It is demonstrated that adsorption of the sulfonated azodye Congo Red confers on A. brasilense the ability to consistently spread in a semiliquid agar and form microcolonies. Spontaneous variants of A. brasilense with rapid swarming are described, as well as variants that swarm in the presence of Congo Red. It is assumed that at least two types of compounds are formed, which are (a) necessary for swarming and/or spreading with the formation of microcolonies and (b) capable of interacting with Congo Red.

[Determination of the structure of the repeated unit of the Azospirillum brasilense SR75 O-specific polysaccharide and homology of the lps loci in the plasmids of Azospirillum brasilense strains SR75 and Sp245].

The structural identity of the repeated unit in O-specific polysaccharides (OPSs) present in the outer membrane of strain SR75 of the bacterium Azospirillum brasilense, isolated from wheat rhizosphere in Saratov oblast, and the OPSs of previously studied A. brasilense strain Sp245, isolated from surface-sterilized wheat roots in Brazil, has been demonstrated. Plasmid profiles, DNA restriction, and hybridization assays suggested that A. brasilense strains SR75 and Sp245 have different genomic structures. It was shown that homologous lps loci of both strains was localized in their plasmid DNA. This fact allows us to state that, despite their different origin, the development of the strains studied was convergent. Presumably, the habitation of these bacteria in similar ecological niches influenced this process in many respects.

[Analysis of DNA, lipopolysaccharide structure, and some cultural and morphological properties in closely related strains of Azospirillum brasilense].

We studied closely related Azospirillum brasilense strains Sp7 and Cd. For probing of their genomes, the fragments of 85-MDa (p85) and 120-MDa (p120) from A. brasilense Sp245 plasmids were hybridized with 115-MDa (p115) and 90-Mda (p90) plasmids of strain Sp7, respectively. Strain Cd was found to lose the 115-Mda plasmid and one of the two EcoRI restriction fragments of the total DNA (localized within p115 and the chromosome) that was homologous to an EcoRI-generated p85 fragment of 2.4 kb. On the contrary, in the total DNA of strain Sp7-S, in spite of the previously established disappearance of the 115-Mda replicon, two fragments homologous to p85 were revealed, as with strain Sp7. It is suggested that the Sp7-S genome contains the total p115 DNA or at least a certain part of it. Strains Sp7 and Cd were found to differ in size and morphology of colonies on solid and semisolid media, in the levels of resistance to a cation surfactant cetavlon, and in the antigen structure of lipopolysaccharides.

[The use of fragments of the 85- and 120-MDa plasmids of Azospirillum brasilense Sp245 to study the plasmid rearrangement in this bacterium and to search for homologous sequences in plasmids of Azospirillum brasilense Sp7]. / Ispol'zovanie fragmentov 85- i 120-MDa plazmid Azospirillum brasilense Sp245 dlia izucheniia plazmidnoi perestroiki u étoi bakterii i dlia poiska gomologichnykh posledovatel'nostei v plazmidakh Azospirillum brasilense Sp7.

A spontaneous loss of the 85- (p85) and 120-MDa (p120) replicons and simultaneous generation of a plasmid of more than 300 MDa were associated with defects in synthesis of O-specific and Calcofluor-binding polysaccharides and had no effect on flagellation and motility of the Azospirillum brasilense Sp245.5 mutant. The plasmid rearrangement was studied by hybridization of DNAs from the wild-type Sp245 strain and the Sp245.5 mutant with p85 and p120 fragments that contained loci involved in formation of the polar (fla) and lateral (laf) flagella, synthesis of O-specific and Calcofluor-binding polysaccharides (lps/cal), swimming (mot), and swarming (swa) of bacteria. Hybridization with the p120 fragments revealed incorporation of the intact fla/swa loci and the altered lps/cal loci into a new megaplasmid. Two EcoRI fragments homologous to the fla/laf/mot/swa loci of p85 were found in A. brasilense Sp245 DNA, whereas only one copy was preserved in the Sp245.5 mutant. Hybridization of the p120 and p85 fragments of Sp245 to the A. brasilense Sp7 DNA for the first time revealed regions of substantial homology to these fragments in the 90- and 115-MDa Sp7 plasmids, respectively.

[Effect of integrating the pJFF350 vector into the 85-MDa plasmid of Azospirillum brasilense Sp245 on bacterial flagellation and mobility]. / Vliianie integratsii vektora pJFF350 v 85-MDa plamidu Azospirillum brasilense Sp245 na zhgutikovanie i podvizhnost' bakterii.

Results of genetic analysis of three derivatives of Azospirillum brasilense Sp245 (strains BK570, SK051, and SK248) carrying cointegrates of plasmids 85-MDa and pJFF350 (the vector for omegon mutagenesis), which manifest abnormalities in flagellation and motility, are presented. It was shown for the first time that the integration of the suicide vector into one of Azospirillum resident plasmids is accompanied by the formation of various fusion products and changes in flagellation and motility of these bacteria, such as the loss of the polar (Fla) and lateral (Laf) flagella in SK051; inactivation of Fla and Laf in SK248; and Fla-dependent acceleration of expansion in semiliquid media in BK570.

[Complementation analysis of mutants of the associative bacteria Azospirillum brasilense Sp245 and S27, defective in mobility and flagellation]. / Komplementatsionnyi analiz mutantov assotsiativnykh bakterii Azospirillum brasilense Sp245 i S27, defektnykh po podvizhnosti i zhgutikovaniiu.

Three mutants of Azospirillum brasilense Sp245 incapable of both formation of the polar flagellum (Fla-phenotype) and swarming in semisolid media (Swa-phenotype) were characterized. These mutants were shown to have lost the 85-MDa plasmid and to carry the Tn5-Mob transposon and pSUP5011 vector in different regions of their genomes. With the use of A. brasilense Sp245 gene bank, the capacity for both polar flagellum formation and swarming was restored in the above mutants and in the previously generated transposon mutants A. brasilense Sp245 and S27. The transconjugants obtained were only slightly motile in the liquid culture. In the gene bank of Sp245, the recombinant plasmids carrying wild-type fla/swa loci were identified.

[Effect of plasmid composition on the chemotaxis reaction of Azospirillum brasilense Sp245 associated with gramineae]. / Vliianie plazmidnogo sostava na reaktsii khemotaksisa assotsiirovannykh so zlakami bakterii Azospirillum brasilense Sp245.

Correlation between the loss of the 120 and/or 130 kb plasmids by the spontaneous Azospirillum brasilense mutant and appearance of the Che(-)-phenotype towards 9-mono- and disaccharides has been established. The plasmid rearrangement is concomitant with the appearance of a new 44 Kda protein among the membrane proteins of azospirilli. Chemotaxis to alanine, glutamic acid, and to organic acids is not impaired.