Search

Strain Az39 T of Azospirillum is a diazotrophic plant growth-promoting bacterium isolated in 1982 from the roots of wheat plants growing in Marcos Juárez, Córdoba, Argentina. It produces indole-3-acetic acid in the presence of l-tryptophan as a precursor, grows at 20-38 °C (optimal 38 °C), and the cells are curved or spiral-shaped, with diameters ranging from 0.5-0.9 to 1.8-2.2 µm. They contain C 16 : 0 , C 18 : 0 and C 18 : 1  ω 7 c / ω 6 c as the main fatty acids. Phylogenetic analysis of its 16S rRNA gene sequence confirmed that this strain belongs to the genus Azospirillum , showing a close relationship with Azospirillum baldaniorum Sp245 T , Azospirillum brasilense Sp7 T and Azospirillum formosense CC-Nfb-7 T . Housekeeping gene analysis revealed that Az39 T , together with five strains of the genus (Az19, REC3, BR 11975, MTCC4035 and MTCC4036), form a cluster apart from A. baldaniorum Sp245 T , A. brasilense Sp7 T and A. formosense CC-Nfb-7 T . Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) between Az39 T and the aforementioned type strains revealed values below 96 %, the circumscription limit for the species delineation (ANI: 95.3, 94.1 and 94.0 %; dDDH: 62.9, 56.3 and 55.6 %). Furthermore, a phylogeny evaluation of the core proteome, including 809 common shared proteins, showed an independent grouping of Az39 T , Az19, REC3, BR 11975, MTCC4035 and MTCC4036. The G+C content in the genomic DNA of these six strains varied from 68.3 to 68.5 %. Based on the combined phylogenetic, genomic and phenotypic characterization presented here, we consider that strain Az39 T , along with strains Az19, REC3, BR 11975, MTCC4035 and MTCC4036, are members of a new Azospirillum species, for which the name Azospirillum argentinense sp. nov. is proposed. The type strain is Az39 T (=LBPCV39 T =BR 148428 T =CCCT 22.01 T ).

The article presents a study on the role of alkyl hydroperoxide reductase in Azospirillum (A.) brasilense Sp245. A. brasilense, a gram-negative nitrogen-fixing proteobacterium, is used in the growth of agricultural crops. The study intends to determine the increased sensitivity to oxidative stress when gene encoding AhpC is inactivated. This has been associated to the alkyl hydroperoxide reductase because of its characteristic of being more sensitive to oxidative stress. Moreover, the increased oxidative stress has been viewed as a factor for the cellular changes, cell aggregation and flocculation.

The article presents a study which describes an Azospirillium brasilense Sp7 mutant strain with disablement of the pRhico-located gene wzm in lipopolysaccharide synthesis (LPS). The study found several differences between wild-type and mutant strains in exopolysaccharide (EPS) monosaccharide composition, but observed no significant differences between them in EPS amount. The study also found that the wzm mutant was more resistant to oxidative stress, starvation, desiccation, osmotic shock and heat than the wild-type. Moreover, the study attributed the pleiotropic phenotypic changes observed in the wzm mutant to its altered LPS relative to the wild-type.

The article examines the mechanism of an extra-cytoplasmic function sigma factor and anti-sigma factor control carotenoid biosynthesis in strains Sp7 and Cd of Azospirillum brasilense. The researchers observed that colonies of strain Cd is synthesis of carotenoids which yielded orange-pink coloured while colonies of strain Sp7 had a white-cream colour on plates. The upstream region of the Tn5-mutated open reading frame (ORF) contained another (ORF) that synthesized an extra-cytoplasmic function (ECF)-class factor. In conclusion, the researchers noted that the operon that includes the rpoE gene in the specimen is bicistronic.

The article presents a study on the promoter-trap identification of wheat seed extract-induced genes in the plant-growth-promoting rhizobacterium Azospirillum brasilense Sp245. This paper focuses on the strains used in cereal crops although their root adaptations are not fully known. A global approach was applied in this study based on differential fluorescence induction (DFI) promoter trapping for identifying genes of the wheat isolate Azospirillum brasilense Sp245. They are induced with the spring wheat seed extracts. The amounts of nitrate and nitrite present in spring wheat extracts for upregulation and plant interactions of Azospirillum genes were observed further.

Tn5 mutagenesis was used to generate an Azospirillum brasilense SPF94 mutant. Genetic analysis of this mutant revealed that a homologue of the mreB gene, which controls cell shape in Bacillus subtilis and Escherichia coli, was inactivated. The cell-surface properties of the mutant were different from those of the parental strain. The mutant colonies were highly fluorescent when grown on plates containing Calcofluor White. Light and electron microscopy revealed that the mutant cells were round and had thicker capsules than the spiral parental strain. The mutants contained up to ten times more capsule protein than the parental strain, but lacked a 40 kDa protein that is abundant in the parental strain. The phenotype of the isolated mutant resembled that of the cyst-like differentiated forms of Azospirillum, suggesting that the mreB homologue could be involved in differentiation. [ABSTRACT FROM AUTHOR]

Azospirillum lipoferum RG20, a nitrogen-fixing bacterium found in all kind of soils, was found to be naturally resistant to penicillins and cephalosporins. 6-β-Bromopenicillanic acid, an irreversible inhibitor of serine-β-lactamases, completely abolished this resistance. A β-lactamase was purified 518-fold from a cell-free extract of A. lipoferum RG20. A single band on SDS-PAGE (apparent molecular mass 31 000 Da) and on isoelectric focussing (p 19.35) was observed with the purified protein. The enzyme hydrolysed benzylpenicillin, ampicillin, cephalothin and cephaloridine with comparable k[sub cat] values and catalytic efficiencies. However, carbenicillin and cefotaxime were hydrolysed with significantly lower kinetic parameters and oxacillin was hydrolysed at a rate 100 times slower. The purified β-lactamase was inhibited by clavulanic acid and sutbactam but not by EDTA or aztreonam. Its substrate and inhibitor profiles are consistent with those of the broadspectrum β-lactamases inhibited by clavulanic acid (group 2b of the Bush-Jacoby-Medeiros scheme). The effect of pH on k[sub cat] and K[sub m] values for benzylpenicillin hydrolysis was studied. The dependence of k[sub cat] on pH suggests that the enzyme-substrate (ES) complex must be in at least three protonation states: two with k[sub cat] values equal to 2800 and 1450 s[sup -1] and a third inactive one [pK[sub 1](ES) 4.7 and pK[sub 2](ES) 7.9]. Similarly, the dependence of k[sub cat]/K[sub m] on pH can be explained by postulating that the enzyme free form can be at least in three different protonation states: two of them with k[sub cat]/K[sub m] values equal to 2.7 × 10[sup 6] and 3.7 × 10[sup 8] M and a third one unable to productively bind substrate. Interestingly, the dependence of k[sub cat]/K[sub m] on pH is consistent with positive cooperativity for proton binding to the enzyme free form [pK[sub i](E) 8.5 and pK[sub 2](E) 7.2]. [ABSTRACT FROM AUTHOR]

Investigates the biological mechanisms involved in the aggregation of Azospirillum brasilense strain Cd. Synthesis of cells under aggregation-inducing and non-aggregation-inducing conditions; Aggregation specific activities of outer-membrane protein and total membrane fractions; Involvement of outer-membrane protein in aggregation of cells of Azospirillum brasilense.

Focuses on the analysis by means of the gusA fusion plasmids, described as the primary colonization of the root hair zones of wheat by A. brasilense mutants deficient, in an attempt to examine the specific role of bacterial motility and wheat root attachment in the Azospirillum-plant root interaction. Ability of the bacteria of the genus Azospirillum; Exhibition of a strongly reduced colonization ability as compared to the wild-type.

Presents a technique which enables the study of aggregation of Azospirillum brasilense (A. brasilense). Role of bacterial surface in the establishment of bacterial--plant associations; Definition of cell aggregation; Quantitative measurement of aggregation of various A. brasilense strains.

Describes an approach studying the full sequence of acyl carrier protein (ACP) P, the gene encoding ACP of Azospirillum brasilense. Role of ACPs in bacterial fatty acid synthesis; Obtainment of nucleotide sequence by cloning and sequencing inverse polymerase chain reaction (PCR); Deduction of primary structure of A. brasilense ACP.

Reports that in an effort to better understand the role of the compounds produced by azospirillum brasilense, the adhesion of azospirillum brasilense to inert surfaces was investigated. Adhesion's dependence on time and temperature; Influence of cell physiology demonstration; Scanning electron microscopy as an examination of the morphology of adhering cells; Acknowledgements; References.

Demonstrates the glycosylation of the flagellin of the polar flagellum of Azospirillum brasilense Sp7. Bacterial strains and growth conditions; Chemical deglycosylation of flagellin; Sugar staining of blotted proteins; Immunogold labelling of whole cells and transmission electron microscopy.

Characterizes monoclonal antibodies with high specificity for Azospirillum brasilense Sp7, and which bind to different antigenic determinants using Western blot techniques. Isolation of A. brasilense polar and lateral flagella; Outer-membrane protein isolation; Lipopolysaccharide extraction; Immunogold labeling and transmission electron microscopy.

Nitrogen-fixing bacterial strain, designated B2 T , was isolated from methane-oxidation enrichment originating from a Sphagnum -dominated raised peatland in Tver region, Russia, and its phenotypic, chemotaxonomic and genomic characteristics were investigated. Cells of isolate were Gram-negative, aerobic, rod or spiral-shaped, with motility provided by a single polar flagellum in liquid media and peritrichous flagella on solid media. Strain was able to grow at 15-40 °C, pH 5.5-8.5 and tolerated NaCl to 2.0 % (w/v). Strain B2 T gave positive amplification for dinitrogen reductase ( nifH gene) and acetylene reduction activity was recorded up to 1250 nmol ethylene h -1 (mg protein) -1 . Analysis of 16S rRNA showed that B2 T represents a member of the genus Azospirillum and had the highest sequence similarity with A. humicireducens SgZ-5 T (97.92 %). The predominant quinone system was ubiquinone Q-10 and the major fatty acids were C 18 : 1 ω7, C 16 : 1 ω7 and C 16 : 0 . The strain was facultative methylotrophic and used methanol and formate for the growth. Genome sequencing revealed a genome size of 8.0 Mbp and a G+C content of 67.8 mol%. The mx aFI genes encoding methanol dehydrogenase were absent, but a homologous xox F gene was detected. The genes encoding enzymes involved in the biosynthesis of tetrahydromethanopterin (H 4 MPT) (formaldehyde oxidation) and NAD-linked formate dehydrogenase ( fdsABG ) were identified. Pairwise determined whole genome average nucleotide identity (gANI) values confirmed that strain B2 T represents a novel species, for which we propose the name Azospirillum palustre sp. nov. with the type strain B2 T (VKM B-3233 T , КСТС 62613 Т ).