Transposon mutagenesis, elimination and mobilization of plasmids in nitrogen-fixating bacterium Azospirillum brasilense Sp245

The expressed difference in the plasmid profile of A. brasilense Sp245 is registered as a result of Tn5-Mob-mutability. Integration of the vector pSUP5011 into one of the A. brasilense Sp245 plasmid and using of the Tn5-Mob transposon to mobilize the 85Md cryptic plasmid are reported. The properties of A. brasilense Sp245 with the mutant plasmids composition (surface structure, acetylene and nitrate reduction, ability to a number of carbohydrates utilization, formation of melanin, antibiotics resistance specter) have been analyzed. The transposon Tn5-Mob insertion into the 85Md plasmid resulted in isolation of a mutant excreting a melanin-like pigment into the medium. The results suppose 85Md plasmid participation in melaninogenesis.     

Effect of integrating the pJFF350 vector into the 85-MDa plasmid of Azospirillum brasilense Sp245 on bacterial flagellation and mobility

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

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.     

Search for conjugative plasmids in Azospirillum brasilense and Azospirillum lipoferum associated with plants

The conjugative plasmids in Azospirillum brasilense strains S17. Sp107, Sp245, SpBr14, JM6B2, JM82Al, UQ1794, UQI796 and in Azospirillum lipoferum strain RG20 were prove to exist for the first time in connection with their potency to mobilize a non-conjugative IncQ-plasmid pVZ361 from IncQ-group (ori RSF1010, KmR, SuR. 11.4 kb) for conjugated transfer to aplasmid strains Agrobacterium tumefaciens and Pseudomonas putida at high frequencies.     

Formation of Polar Bundles of Pili and the Behavior of Azospirillum brasilenseCells in a Semiliquid Agar

This paper describes the formation of single polar bundles of pili on Azospirillum brasilensecells, the twitching motility of cell aggregates, and a new type of social behavior—the dispersal of bacterial cells in semiliquid agar associated with the formation of granular inclusions (the so-called Gri⁺phenotype)—which is an alternative to swarming (the Swa phenotype). The wild-type A. brasilensecells occurring in a semiliquid agar may show either the Swa⁺Gri^–, or Swa^–Gri^–, or Swa^–Gri⁺phenotype. The formation of single polar flagella (Fla) or polar bundles of pili may reflect two alternative states of A. brasilensecells. The components of the Fla system may be involved in the regulation of the phenotypic variation of azospirilla.     

红腹锦鸡肺的组织结构与微血管构筑

为了了解红腹锦鸡(Chroysolophus pictus)肺的微细结构和微血管构筑特征,为呼吸生物学研究提供形态学依据,用组织学方法和微血管铸型技术在光镜和扫描电镜下观察研究了红腹锦鸡肺的组织结构与微血管构筑情况。结果表明,红腹锦鸡肺主要由各级支气管构成,从三级支气管上呈辅射状分出许多呼吸毛细管(微气管),并相互吻合成网状,呼吸毛细管外面包围有丰富的毛细血管;红腹锦鸡肺毛细血管垂直围绕在各微气管外,并相互吻合成密集的立体微血管网;毛细血管管径4.5~7.0μm,微气管直径11~50μm。并对肺微血管构筑情况与呼吸效率的关系作了探讨。     

Alterations in the primary structure of an 85-MDa plasmid affecting flagellation and motility in the bacterium <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> Sp245

Earlier, such Azospirillum brasilense Sp245 mutants as flagellation-defective SK051, SK248 with paralyzed flagella, and BK570 swimming and swarming faster than Sp245 were obtained. In SK051 and SK248, the suicide vector pJFF350 integrated into the 18.3-kb XhoI fragment of an 85-MDa plasmid (p85) while in BK570, it integrated into the 9.1-kb XhoI-fragment of p85. In the present work, analysis of the nucleotide sequence of fusion products of p85 and pJFF350 was performed. In p85, in addition to three IS elements (two of which mediated cointegrate formation) and phage integrase gene, 22 open reading frames with coding properties were identified. Possible participation of predicted translation products of several p85 genes in determination of bacterial motility is discussed. Since differences in the primary structure of p85::pJFF350 cointegrates from SK051 and SK248 cells are localized within pJFF350 DNA, different effects of DNA-folding changes on the expression of corresponding p85 genes are suggested.