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At least 19 recordsLinked to original sources
PubMed1978

A taxonomic study of the Spirillum lipoferum group, with descriptions of a new genus, Azospirillum gen. nov. and two species, Azospirillum lipoferum (Beijerinck) comb. nov. and Azospirillum brasilense sp. nov.

Sixty-one strains of the root-associated nitrogen fixer Spirillum lipoferum exhibited a similar morphology in peptone--succinate salts medium: vibrioid cells having a diameter of 1.0 micrometer. When grown in broth the cells had a single polar flagellum, but when grown on agar at 30 degrees C lateral flagella of shorter wavelength were also formed. The DNA base composition was 69--71 mol% guanine + cytosine when determined by thermal denaturation. DNA homology experiments indicated the occurrence of two distinct but related homology groups: 46 strains were in group I and 15 strains were in group II. Group II strains were distinguished by their ability to use glucose as a sole carbon source for growth in nitrogen-free medium, by their production of an acidic reaction in a peptone-based glucose medium, by their requirement for biotin, and by their formation of wider, longer, S-shaped or helical cells in semisolid nitrogen-free malate medium. The results indicate that two species exist, and on the basis of their characteristics it is proposed that they be assigned to a new genus, Azospirillum. Strians belonging to group II are named A. lipoferum (Beijerinck) comb. nov., while those belonging to group I are named A. brasilense sp. nov. Strain Sp 59b (ATCC29707) is proposed as the neotype strain for A. lipoferum, and strain Sp 7 (ATCC 29145) is proposed as the type strain for A. brasilense.

Culture Media↗
PubMed1994

Molecular relationship of an atypical Azospirillum strain 4T to other Azospirillum species.

DNA/DNA hybridization, plasmid content and partial 16S rDNA sequence were determined to confirm the relationship between two Azospirillum strains, 4B and 4T, isolated from the same rice rhizosphere. The partial 16S rDNA sequence was determined for 9 strains belonging to 5 Azospirillum species which included Azospirillum lipoferum strains 4B and 4T, and was compared to a set of ribosomal sequences from other bacteria of the alpha subdivision of the Proteobacteria. Four Azospirillum species sequences were found to form a coherent group, whereas A. halopraeferens was found to be more divergent. The five Azospirillum species were closely related to Magnetospirillum and to a lesser extent to Rhodospirillum, with which they share some morphological features. The partial 16S rDNA sequences of the two strains 4B and 4T were identical and confirmed the closeness of these two strains. Plasmid content and DNA/DNA hybridization data (S1 nuclease and delta Tm) grouped Azospirillum strains 4B and 4T with the other strains of species Azospirillum lipoferum (USA5a, 59b, BR17). Other biochemical and genetic characters confirmed the grouping of Azospirillum strains 4B and 4T together with A. lipoferum.

Azospirillum↗
PubMed2026

Description of two nitrogen-fixing bacteria, Azospirillum mesophilum sp. nov. and Azospirillum terrae sp. nov., isolated from paddy soils.

Two novel aerobic, rod-shaped, motile bacterial strains, designated as sgz302134T and sgz301742T, were isolated from paddy soil in Fujian Province. Strains sgz302134T and sgz301742T shared the highest 16S rRNA gene sequence similarities with the type strains Azospirillum isscasi C340-1T (98.2%) and Azospirillum thiophilum DSM 21654T (97.4%), respectively. The phylogenetic tree based on 16S rRNA gene sequences showed that two strains clustered with members of the genus Azospirillum. Growth of strains sgz302134T and sgz301742T was observed at 10-45 °C, pH 5.0-9.5 and 0-0.5% (w/v) NaCl and 15-37 °C, pH 6.0-9.0 and 0-1.0% (w/v) NaCl, respectively. Strains sgz302134T and sgz301742T contained Q-10 as the main quinone. The main fatty acids (>10%) of both strains were summed feature 2 (C12 : 0 aldehyde), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and C16 : 0. The genomic DNA G+C content of strains sgz302134T and sgz301742T was 68.4 and 68.3%, respectively. The digital DNA-DNA hybridization and average nucleotide identity values between the two strains and their related reference strains were 27.8 and 87.4% and 22.0 and 84.3%, respectively. Both strains possessed nif genes nifBDEHKN. Based on the above results, these two strains represent two novel species of the genus Azospirillum, for which the names Azospirillum mesophilum sp. nov. and Azospirillum terrae sp. nov. are proposed. The type strains are sgz302134T (=MCCC 1K09520T=KCTC 8840T) and sgz301742T (=MCCC 1K09804T=KCTC 18149T), respectively.

Soil Microbiology↗
PubMed1987

Transposon Mutagenesis of Azospirillum brasilense and Azospirillum lipoferum: Physical Analysis of Tn5 and Tn5-Mob Insertion Mutants.

Tn5-induced insertion mutants were generated in Azospirillum brasilense Sp7 and A. lipoferum SpBr17 by mating with Escherichia coli strains carrying suicide plasmid vectors. The sources of Tn5 were the suicide plasmids pGS9 and pSUP2021. Kanamycin-resistant Azospirillum colonies appeared from crosses with E. coli at maximum frequencies of 10 per recipient cell. Transposon Tn5 also conferred streptomycin resistance on Azospirillum colonies as was observed earlier for Rhizobium sp. Eight Tn5-induced Km SmA. brasilense Sp7 mutants with reduced nitrogen-fixing capacity were isolated. The potential use of Tn5-Mob for labeling and mobilization of Azospirillum-indigenous plasmids was demonstrated by isolating Tn5-Mob insertions in the megaplasmids of A. brasilense Sp7.

Journal Article↗
PubMed1988

Analysis of Indole-3-Acetic Acid and Related Indoles in Culture Medium from Azospirillum lipoferum and Azospirillum brasilense.

Analysis of neutral and acidic ethyl acetate extracts from culture medium of Azospirillum brasilense 703Ebc by high-performance liquid chromatography (HPLC) and combined gas chromatography-mass spectrometry demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol, indole-3-methanol, and indole-3-lactic acid. IAA in media of 20 strains of A. brasilense and Azospirillum lipoferum was analyzed quantitatively by both the colorimetric Salkowski assay and HPLC-based isotopic dilution procedures. There was little correlation between the estimates obtained with the two procedures. For instance, the Salkowski assay suggested that the culture medium from A. brasilense 703Ebc contained 26.1 mug of IAA ml, whereas HPLC revealed the presence of only 0.5 mug of IAA ml. Equivalent estimates with A. brasilense 204Ed were 10.5 and 0.01 mug of IAA ml, respectively. The data demonstrate that the Salkowski assay is not a reliable method for measuring the IAA content of Azospirillum culture medium and that estimates in excess of 10 mug of IAA ml should be viewed with particular caution. Metabolism of [2'-C]IAA by A. brasilense 703Ebc yielded radiolabeled indole-3-methanol, whereas roots of maize (Zea mays L.) seedlings gave rise to [C]oxindole-3-acetic acid and an array of polar metabolites. Metabolism of [2'-C]IAA by maize roots inoculated with A. brasilense 703Ebc produced a metabolic profile characteristic of maize rather than Azospirillum species.

Journal Article↗
PubMed2001

Azospirillum brasilense and Azospirillum lipoferum hydrolyze conjugates of GA20 and metabolize the resultant aglycones to GA1 in seedlings of rice dwarf mutants.

Azospirillum species are plant growth-promotive bacteria whose beneficial effects have been postulated to be partially due to production of phytohormones, including gibberellins (GAs). In this work, Azospirillum brasilense strain Cd and Azospirillum lipoferum strain USA 5b promoted sheath elongation growth of two single gene GA-deficient dwarf rice (Oryza sativa) mutants, dy and dx, when the inoculated seedlings were supplied with [17,17-2H2]GA20-glucosyl ester or [17,17- 2H2]GA20-glucosyl ether. Results of capillary gas chromatography-mass spectrometry analysis show that this growth was due primarily to release of the aglycone [17,17-2H2]GA20 and its subsequent 3beta-hydroxylation to [17,17-2H2]GA1 by the microorganism for the dy mutant, and by both the rice plant and microorganism for the dx mutant.

Azospirillum↗
PubMedDate not supplied

[Plasmid P85 from Azospirillum brasilense SP245: study of the circle of possible hosts and incompatibility with plasmids from Azospirillum brasilense SP7].

The possibility of the stable inheritance of the plasmid p85 mobilized derivatives from Azospirillum brasilense Sp245 in the cells of the bacterial genera Rizobiaceae (Agrobacterium tumfaciens) and Pseudomonadaceae (Pseudomonas putida) has been shown. The plasmid p85 participates in coding for the physiologically active products (the plant hormones). It is not inherited by the Escherichia coli strains. For the first time the incompatibility of azospirillium plasmids has been demonstrated on the example of the plasmid p85 from Azospirillum brasilense Sp245 and the plasmid p115 from Azospirillum brasilense Sp7.

Agrobacterium tumefaciens↗
PubMed2002

[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.

Azospirillum↗
PubMed1984

Fructose catabolism in Azospirillum brasilense and Azospirillum lipoferum.

The pathways for catabolism of fructose were investigated in the type strains of Azospirillum lipoferum and Azospirillum brasilense grown aerobically with (NH4)2SO4 as the nitrogen source. When grown on fructose, the former species possessed a complete Entner-Doudoroff pathway, whereas the latter species lacked activity for glucose-6-phosphate dehydrogenase. Both species possessed a complete catabolic Embden-Meyerhof-Parnas pathway. Neither species possessed the key enzyme of the hexose monophosphate pathway, 6-phosphogluconate dehydrogenase. Both species could phosphorylate fructose to fructose-1-phosphate by means of a phosphoenolpyruvate-phosphotransferase system, and high activities of 1-phosphofructokinase occurred. Both species possessed glucokinase activity, but only A. lipoferum had hexokinase activity; moreover, the cells of A. brasilense were nearly impermeable to glucose, accounting for the inability of this species to grow on glucose. Both species possessed pyruvate dehydrogenase, a complete tricarboxylic acid cycle, a glyoxylate shunt, and malic enzyme. Analysis of the acidic end products for both species indicated the formation of only small amounts of various organic acids, and most of the titratable acidity was due to utilization of the ammonium ions of the medium. Gluconic acid was not formed during growth of either species on fructose but was detected during growth of A. lipoferum on glucose; this species also possessed an NADP-linked glucose dehydrogenase and gluconokinase.

Biological Transport, Active↗
PubMed1985

Flocculation in Azospirillum brasilense and Azospirillum lipoferum: exopolysaccharides and cyst formation.

The phenomena of flocculation and floc formation by Azospirillum brasilense Sp7 (ATCC 29145) and Azospirillum lipoferum Sp59b (ATCC 29707) were studied in aerobic liquid cultures. Carbon sources representative of various entry pathways in combination with various nitrogen sources induced flocculation in both species of azospirilla. Noticeably, the combination of fructose and nitrate was the most effective in terms of floc yields. Phase-contrast microscopic observations revealed a transition in cell morphology from freely motile, vibrioid cells to nonmotile, highly refractile encysting forms during the formation of flocs. The nonmotile forms in flocs appeared to be entangled within a fibrillar matrix, and the cells were highly resistant to desiccation. Dried flocs kept for almost 6 months still maintained the highly refractile encysting forms, and their viability was confirmed by pellicle formation and acetylene reduction in semisolid malate medium. Electron microscopic observations of the desiccated flocs revealed the presence of cell forms containing abundant poly beta-hydroxybutyrate granules within a central body and surrounded by a thick layer of exopolysaccharides. The latter were characterized by alkali and acid digestion, crude cellulase hydrolysis, and calcofluor staining. It was concluded that the overproduction of exocellular polymers induces the flocculent growth and is associated with the concomitant transformation of vegetative cells to the desiccation-resistant encysting forms under limiting cultural conditions.

Aerobiosis↗
PubMed2002

[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].

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.

Azospirillum brasilense↗
PubMedDate not supplied

[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.

Azospirillum brasilense↗
PubMed1987

Regulation of nitrogenase activity by oxygen in Azospirillum brasilense and Azospirillum lipoferum.

The nitrogenase activity of the microaerophilic bacteria Azospirillum brasilense and A. lipoferum was completely inhibited by 2.0 kPa of oxygen (approximately 0.02 atm of O2) in equilibrium with the solution. The activity could be partially recovered at optimal oxygen concentrations of 0.2 kPa. In contrast to the NH4+ switch off, no covalent modification of the nitrogenase reductase (Fe protein) was involved, as demonstrated by Western-blotting and 32P-labeling experiments. However, the inhibition of the nitrogenase activity under anaerobic conditions was correlated with covalent modification of the Fe protein. In contrast to the NH4+ switch off, no increase in the cellular glutamine pool and no modification of the glutamine synthetase occurred under anaerobic switch-off conditions. Therefore, a redox signal, independent of the nitrogen control of the cell, may trigger the covalent modification of the nitrogenase reductase of A. brasilense and A. lipoferum.

Amino Acids↗
PubMed1989

Calcofluor- and lectin-binding exocellular polysaccharides of Azospirillum brasilense and Azospirillum lipoferum.

Extracellular polysaccharides synthesized by Azospirillum brasilense and A. lipoferum were shown on agar plates and liquid flocculating cultures. The six strains used in this work expressed a mucoid phenotype, yielding positive calcofluor fluorescence under UV light. The calcofluor-binding polysaccharides were distributed between the capsular and exopolysaccharide fractions, suggesting exocellular localization. No calcofluor fluorescence was observed in residual cells after separation of the capsular and exopolysaccharide fractions. Cellulose content was significantly higher in flocculating than in nonflocculating cultures. Failure to induce flocculation by addition of cellulose (100 mg/ml) to nonflocculating cultures, together with the sensitivity of flocs to cellulase digestion, suggested that cellulose is involved in maintenance of floc stability. Different A. brasilense and A. lipoferum strains bound to a wheat lectin (fluorescein isothiocyanate-wheat germ agglutinin), indicating the occurrence of specific sugar-bearing receptors for wheat germ agglutinin on the cell surface. The biochemical specificity of the reaction was shown by hapten inhibition with N-acetyl-D-glucosamine. All six strains failed to recognize fluorescein isothiocyanate-soybean seed lectin under our experimental conditions. We conclude that azospirilla produce exocellular polysaccharides with calcofluor- and lectin-binding properties.

Bacteria↗
PubMed1992

Pectin decomposition and associated nitrogen fixation by mixed cultures of Azospirillum and Bacillus species.

Cocultures of different Azospirillum species with Bacillus polymyxa or Bacillus subtilis allow the efficient utilization of pectin as carbon and energy sources for nitrogen fixation. The nitrogenase activity obtained with cocultures was as high as 30-80 nmol C2H4 h-1 mL-1, a much higher value than that obtained with pure cultures of either Azospirillum (up to 13 nmol C2H4 h-1 mL-1) or B. polymyxa (up to 2 nmol C2H4 h-1 mL-1) alone. To establish to what extent each partner contributed to nitrogenase activity, acetylene reduction was assayed as a function of time and it was also measured on Azospirillum cultivated in the cultures filtrates of the Bacillus. The results suggested that the nitrogenase activity was mostly produced by Azospirillum. The nitrogenase activity occurred at the expense of the degradation and fermentation products of the pectin. The new pectinolytic species, Azospirillum irakense, utilized both degradation and fermentation products of pectin, whereas the nonpectinolytic strains (Azospirillum brasilense, Azospirillum lipoferum, Azospirillum amazonense) utilized only the fermentation products of pectin, including acetic and succinic acids. These cocultures can be considered as metabolic associations, where the Bacillus produces degradation and fermentation products of pectin, which can be used by Azospirillum species.

Azospirillum↗
PubMed2003

Effect of Azospirillum-mediated plant growth promotion on the development of bacterial diseases on fresh-market and cherry tomato.

AIMS: Plant growth-promoting (PGP) activity of two Azospirillum strains and their effects on foliar and vascular bacterial diseases were evaluated on fresh market and cherry tomato. METHODS AND RESULTS: Tomato seeds were inoculated with A. brasilense Sp7 or Azospirillum sp. BNM-65. Four-week-old plants were challenge-inoculated with Clavibacter michiganensis subsp. michiganensis (bacterial canker) or with Xanthomonas campestris pv. vesicatoria (bacterial spot). Azospirillum-induced PGP was greater on cherry than on fresh-market tomato. Cherry tomato was more resistant to bacterial canker but more susceptible to bacterial spot than the fresh-market tomato. Canker severity was not affected by Azospirillum seed treatments. However, leaf- and plant-death were delayed on Azospirillum-treated plants compared with nontreated controls. Azospirillum increased the bacterial spot severity on cherry but not on fresh-market tomato. CONCLUSIONS: PGP was observed on both tomato genotypes, although growth effects were larger on cherry tomato. Also, Azospirillum treatments may alter tomato susceptibility to bacterial diseases. SIGNIFICANCE AND IMPACT OF THE STUDY: The interaction between PGP rhizobacteria like Azospirillum spp., not known to induce systemic resistance, with plant pathogens distantly located is frequently overlooked. This work demonstrates the importance of this kind of evaluation.

Actinomycetales↗