Transformation of Azotobacter vinelandii strains unable to fix nitrogen with Rhizobium spp. DNA

1978 ◽  
Vol 24 (3) ◽  
pp. 209-214 ◽  
Author(s):  
William J. Page
Keyword(s):  
Transcriptional Control ◽  
Deoxyribonucleic Acid ◽  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Spontaneous Reversion ◽  
Mutant Strains ◽  
Rhizobium Spp ◽  
Rhizobium Sp

The phenotypes of Azotobacter vinelandii ATCC 12837 strains defective in nitrogen fixation (Nif−) were characterized by intrageneric transformation with known Nif− strains of A. vinelandii OP. These former mutant strains were used as recipients for intergeneric transformation by deoxyribonucleic acid (DNA) prepared from Rhizobium spp. to determine if the rhizobia would transform the Azotobacter Nif− phenotypes to Nif+. The frequency of Nif+ transformants using Rhizobium DNA was always less than the frequency using Azotobacter wild-type DNA but was greater than the spontaneous reversion frequency. The Azotobacter Nif+ recombinants also were stable. DNA from all of the Rhizobium spp. transformed to Nif+Azotobacter mutants defective in the nitrogenase component I (molybdoferredoxin); however, some recombinants had a lower nitrogenase activity and a delayed nitrogenase depression time. Mutants defective in the pleiotrophic transcriptional control of both nitrogenase components were transformed to Nif+ by the asymbiotic nitrogen fixing Rhizobium sp. 32H1 and 41A1, but not the symbiotic nitrogen-fixing species. The significance of these results and the possible future applications of this system are discussed.

Molybdenum enhancement of nitrogen fixation in a Mo-starved Azotobacter vinelandii Nif− mutant

1982 ◽  
Vol 28 (10) ◽  
pp. 1173-1180 ◽  
Author(s):  
William J. Page ◽  
S. Karen Collinson
Keyword(s):  
Molecular Weight ◽  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Cell Extracts ◽  
In The Wild ◽  
Dinitrogenase Reductase

Molybdenum (Mo)-starved wild-type and Nif− strains of Azotobacter vinelandii reduced acetylene (fixed nitrogen) in Mo-limited nitrogen-free medium. Vanadate enhanced this activity in all of the strains. Molybdate caused repression of nitrogenase activity in the Nif− mutants and enhanced the nitrogenase activity in the wild type. The nitrogenase activity in the Nif− mutant UW3, however, was enhanced by Mo, became maximal after 3 h, and then declined to zero after 10 h of incubation. The activation of nitrogenase by Mo followed a 5- to 10-min lag and was inhibited when streptomycin or rifampin was added with Mo. Examination of Mo-starved nitrogen-fixing UW3 cell extracts by two-dimensional polyacrylamide gel electrophoresis revealed molecular weight 57 000, 50 000, and 30 000 proteins that were Mo and NH4+ repressive. The molecular weight 30 000 protein appeared in the same position on the gel as the wild-type dinitrogenase reductase, although UW3 did not produce this protein under Mo-sufficient nitrogen-fixing conditions. Cell extracts prepared 3 h after Mo addition lacked the molecular weight 57 000 and 50 000 proteins but contained a new protein corresponding to the β subunit of dinitrogenase. When UW3 nitrogenase activity was lost, the dinitrogenase reductase-like protein also was absent. The results suggest that a complex active in nitrogen fixation may form between components of the traditional Mo-sufficient and alternative Mo-starved cell nitrogen fixation systems.

Isolation and characterization of Azotobacter vinelandii mutant strains with potential as bacterial fertilizer

1983 ◽  
Vol 29 (8) ◽  
pp. 973-978 ◽  
Author(s):  
Joyce K. Gordon ◽  
Marty R. Jacobson
Keyword(s):  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Resistant Mutant ◽  
Free Medium ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Mutant Strains ◽  
Resistant Strains ◽  
Resistant Mutants

Mutant strains of Azotobacter vinelandii which might have potential for use as bacterial fertilizer have been isolated and fall into two categories: constitutive mutants that synthesize nitrogenase in the presence of ammonium and mutants that overproduce nitrogenase when grown in nitrogen-free medium. The constitutive mutants described in this paper were isolated from the wild type as methylalanine-resistant strains and express up to 23% of the fully derepressed nitrogenase level when grown in medium containing excess ammonium. By contrast, ammonium-grown cultures of wild type have less than 0.003% of the fully derepressed level. Strains which fix more N2 than the wild type in nitrogen-free medium were isolated as mefhylammonium-resistant mutants. Although the methylammonium-resistant mutant strains fix more N2 than the wild type, they grow no faster. The excess nitrogen produced by these mutants is excreted into the medium, resulting in up to 60% more nitrogen than in the medium of the wild type. Higher nitrogenase activity in the methylammonium-resistant mutant strains was found to be a result of increased levels of nitrogenase protein, suggesting that regulation of nitrogenase synthesis may be altered.

Optimal conditions for induction of competence in nitrogen-fixing Azotobacter vinelandii

1982 ◽  
Vol 28 (4) ◽  
pp. 389-397 ◽  
Author(s):  
William J. Page
Keyword(s):  
Dissolved Oxygen ◽  
Sodium Acetate ◽  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Cell Mass ◽  
Apparent Competition ◽  
Competence Development ◽  
Optimal Conditions ◽  
Nitrogen Fixing ◽  
Ph Range

Competence development in nitrogen-fixing Azotobacter vinelandii cells was optimal at pH 7.2–7.4 which necessitated additional buffering of the iron-limited nitrogen-free competence medium or the addition of a suitable organic acid salt, e.g., sodium acetate. An autolysin was active in this pH range and competent cells were more susceptible to autolysis than the general cell population. Competence development also required restricted aeration of the culture, and only those cultures that attained zero dissolved oxygen became competent. Restricted aeration served to protect the iron-limited cell nitrogenase from oxygen inactivation thus allowing the culture to reach zero dissolved oxygen. The inclusion of additional sources of reductant, e.g., malate, in buffered competence medium resulted in increased respiration and protection of nitrogenase, increased cell mass, and poly-β-hydroxybutyrate synthesis, but decreased competence. A possible explanation for the apparent competition between competence development and nitrogenase activity is discussed.

Plasmid replicons of Rhizobium

2005 ◽  
Vol 33 (1) ◽  
pp. 157-158 ◽  
Author(s):  
L.C. Crossman
Keyword(s):  
Short Review ◽  
Nitrogen Fixing ◽  
Rhizobium Etli ◽  
Free Living ◽  
Leguminous Plants ◽  
Symbiotic Plasmid ◽  
Rhizobium Spp ◽  
Plasmid Replicons ◽  
Rhizobium Sp

Rhizobium spp. are found in soil. They are both free-living and found symbiotically associated with the nodules of leguminous plants. Traditionally, studies have focused on the association of these organisms with plants in nitrogen-fixing nodules, since this is regarded as the most important role of these bacteria in the environment. Rhizobium sp. are known to possess several replicons. Some, like the Rhizobium etli symbiotic plasmid p42d and the plasmid pNGR234b of Rhizobium NGR234, have been sequenced and characterized. The plasmids from these organisms are the focus of this short review.

Inactivation of the Crp/Fnr Family of Regulatory Genes in Listeria monocytogenes Strain F2365 Does Not Alter Its Heat Resistance at 60°C†

2006 ◽  
Vol 69 (11) ◽  
pp. 2758-2760 ◽  
Author(s):  
DARRELL O. BAYLES ◽  
GAYLEN A. UHLICH
Keyword(s):  
Listeria Monocytogenes ◽  
Heat Resistance ◽  
Thermal Tolerance ◽  
Type Strain ◽  
Transcriptional Control ◽  
Wild Type Strain ◽  
Gene Cassette ◽  
Wild Type ◽  
Mutant Strains ◽  
Virulence Regulator

A surprising facet of the Listeria monocytogenes genome is the presence of 15 genes that code for regulators in the Crp/Fnr family and include the virulence regulator PrfA. The genes under the transcriptional control of these regulators are currently undetermined, with the exception of some genes controlled by the major virulence regulator PrfA. Using 12 strains of L. monocytogenes, each with an inserted gene cassette that interrupts and renders nonfunctional a different L. monocytogenes strain F2365 Crp/Fnr regulator, we heat challenged each strain at 60°C with an immersed-coil heating apparatus, modeled the survivor data to calculate the underlying mean and mode of the heat resistance distribution for each strain, and compared the thermal tolerance of each mutant to the wild-type strain to determine if any of the Crp/Fnr mutants demonstrated altered heat tolerance. All 12 of the Crp/Fnr mutant strains tested had heat resistance characteristics similar to the wild-type strain (P > 0.05), indicating that mutations in these Crp/Fnr genes neither increased nor decreased the sensitivity of L. monocytogenes strain F2365 to mild heat.

scholarly journals Uncovering New Metabolic Capabilities of Bacillus subtilis Using Phenotype Profiling of Rifampin-Resistant rpoB Mutants

2007 ◽  
Vol 190 (3) ◽  
pp. 807-814 ◽  
Author(s):  
Amy E. Perkins ◽  
Wayne L. Nicholson
Keyword(s):  
Bacillus Subtilis ◽  
Rna Polymerase ◽  
Metabolic Profiling ◽  
Transcriptional Control ◽  
Β Subunit ◽  
Subunit Gene ◽  
Wild Type ◽  
Mutant Strains ◽  
Utilization Patterns ◽  
Flow Of Information

ABSTRACT RNA polymerase is a central macromolecular machine controlling the flow of information from genotype to phenotype, and insights into global transcriptional regulation can be gained by studying mutational perturbations in the enzyme. Mutations in the RNA polymerase β subunit gene rpoB causing resistance to rifampin (Rifr) in Bacillus subtilis were previously shown to lead to alterations in the expression of a number of global phenotypes known to be under transcriptional control, such as growth, competence for transformation, sporulation, and germination (H. Maughan, B. Galeano, and W. L. Nicholson, J. Bacteriol. 186:2481-2486, 2004). To better understand the global effects of rpoB mutations on metabolism, wild-type and 11 distinct congenic Rifr mutant strains of B. subtilis were tested for utilization of 95 substrates by use of Biolog GP2 MicroPlates. A number of alterations of substrate utilization patterns were observed in the Rifr mutants, including the utilization of novel substrates previously unknown in B. subtilis, such as gentiobiose, β-methyl-d-glucoside, and d-psicose. The results indicate that combining global metabolic profiling with mutations in RNA polymerase provides a system-wide approach for uncovering previously unknown metabolic capabilities and further understanding global transcriptional control circuitry in B. subtilis.

scholarly journals Transcriptional Analysis of an Ammonium-Excreting Strain of Azotobacter vinelandii Deregulated for Nitrogen Fixation

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Brett M. Barney ◽  
Mary H. Plunkett ◽  
Velmurugan Natarajan ◽  
Florence Mus ◽  
Carolann M. Knutson ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Stationary Phase ◽  
Gene Transcription ◽  
Biological Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Content Type ◽  
Ammonium Production ◽  
Biological Nitrogen

ABSTRACT Biological nitrogen fixation is accomplished by a diverse group of organisms known as diazotrophs and requires the function of the complex metalloenzyme nitrogenase. Nitrogenase and many of the accessory proteins required for proper cofactor biosynthesis and incorporation into the enzyme have been characterized, but a complete picture of the reaction mechanism and key cellular changes that accompany biological nitrogen fixation remain to be fully elucidated. Studies have revealed that specific disruptions of the antiactivator-encoding gene nifL result in the deregulation of the nif transcriptional activator NifA in the nitrogen-fixing bacterium Azotobacter vinelandii, triggering the production of extracellular ammonium levels approaching 30 mM during the stationary phase of growth. In this work, we have characterized the global patterns of gene expression of this high-ammonium-releasing phenotype. The findings reported here indicated that cultures of this high-ammonium-accumulating strain may experience metal limitation when grown using standard Burk's medium, which could be amended by increasing the molybdenum levels to further increase the ammonium yield. In addition, elevated levels of nitrogenase gene transcription are not accompanied by a corresponding dramatic increase in hydrogenase gene transcription levels or hydrogen uptake rates. Of the three potential electron donor systems for nitrogenase, only the rnf1 gene cluster showed a transcriptional correlation to the increased yield of ammonium. Our results also highlight several additional genes that may play a role in supporting elevated ammonium production in this aerobic nitrogen-fixing model bacterium. IMPORTANCE The transcriptional differences found during stationary-phase ammonium accumulation show a strong contrast between the deregulated (nifL-disrupted) and wild-type strains and what was previously reported for the wild-type strain under exponential-phase growth conditions. These results demonstrate that further improvement of the ammonium yield in this nitrogenase-deregulated strain can be obtained by increasing the amount of available molybdenum in the medium. These results also indicate a potential preference for one of two ATP synthases present in A. vinelandii as well as a prominent role for the membrane-bound hydrogenase over the soluble hydrogenase in hydrogen gas recycling. These results should inform future studies aimed at elucidating the important features of this phenotype and at maximizing ammonium production by this strain.

scholarly journals Transcriptional activation of the Azotobacter vinelandii polyhydroxybutyrate biosynthetic genes phbBAC by PhbR and RpoS

Microbiology ◽  
2011 ◽  
Vol 157 (11) ◽  
pp. 3014-3023 ◽  
Author(s):  
Alberto Hernandez-Eligio ◽  
Mildred Castellanos ◽  
Soledad Moreno ◽  
Guadalupe Espín
Keyword(s):  
Stationary Phase ◽  
Transcriptional Activation ◽  
Azotobacter Vinelandii ◽  
Transcriptional Regulator ◽  
Gene Fusions ◽  
Wild Type ◽  
Rt Pcr ◽  
Regulation Of Expression ◽  
Expression Studies ◽  
Mutant Strains

We previously showed that in Azotobacter vinelandii, accumulation of polyhydroxybutyrate (PHB) occurs mainly during the stationary phase, and that a mutation in phbR, encoding a transcriptional regulator of the AraC family, reduces PHB accumulation. In this study, we characterized the roles of PhbR and RpoS, a central regulator during stationary phase in bacteria, in the regulation of expression of the PHB biosynthetic operon phbBAC and phbR. We showed that inactivation of rpoS reduced PHB accumulation, similar to the phbR mutation, and inactivation of both rpoS and phbR resulted in an inability to produce PHB. We carried out expression studies with the wild-type, and the rpoS, phbR and double rpoS-phbR mutant strains, using quantitative RT-PCR, as well as phbB : : gusA and phbR : : gusA gene fusions. These studies showed that both PhbR and RpoS act as activators of phbB and phbR, and revealed a role for PhbR as an autoactivator. We also demonstrated that PhbR binds specifically to two almost identical 18 bp sites, TGTCACCAA-N4-CACTA and TGTCACCAA-N4-CAGTA, present in the phbB promoter region. The activation of phbB and phbR transcription by RpoS reported here is in agreement with the observation that accumulation of PHB in A. vinelandii occurs mainly during the stationary phase.

Competitive ability, effectiveness, and succinate – triphenyl tetrazolium chloride reductase activity of mutant strains of chick-pea (Cicer arietinum L.) Rhizobium sp.

1983 ◽  
Vol 29 (7) ◽  
pp. 735-745 ◽  
Author(s):  
Raman Rai ◽  
V. Prasad ◽  
S. D. Sharma ◽  
I. C. Shukla
Keyword(s):  
Competitive Ability ◽  
Nitrogenase Activity ◽  
Reductase Activity ◽  
Triphenyl Tetrazolium Chloride ◽  
Tetrazolium Chloride ◽  
Chick Pea ◽  
Cicer Arietinum L ◽  
Reactive Iron ◽  
Mutant Strains ◽  
Rhizobium Sp

Chick-pea Rhizobium strain RG 4 was treated with 200 μg/mL of N-methyl-N-nitro-N′-nitrosoguanidine and 14 mutant strains isolated. Two mutant strains were found to be nonnodulating in the absence of certain amino acids. On the basis of nodulation, two mutant strains (M 38 and M 46) were found to be equally competitive against each other. Mutant strains M 38 and M 46 when applied together produced the maximum nodulation, nitrogenase activity, phenanthroline-reactive iron, and least tetrazolium reductase activity as compared to other pairwise combinations of mutant strains. It was also observed that the correlation between tetrazolium reductase and nitrogenase activity was highly negative.

scholarly journals Synthesis of the Flavonoid-Induced Lipopolysaccharide of Rhizobium Sp. Strain NGR234 Requires Rhamnosyl Transferases Encoded by Genes rgpF and wbgA

2011 ◽  
Vol 24 (12) ◽  
pp. 1513-1521 ◽  
Author(s):  
Silvia Ardissone ◽  
K. Dale Noel ◽  
Mitchell Klement ◽  
William J. Broughton ◽  
William J. Deakin
Keyword(s):  
Vigna Unguiculata ◽  
Wild Type ◽  
Symbiotic Interaction ◽  
Leguminous Plants ◽  
Glycosyl Transferase ◽  
The Core ◽  
O Antigen ◽  
Symbiotic Interactions ◽  
Mutant Strains ◽  
Rhizobium Sp

In the presence of flavonoids, Rhizobium sp. strain NGR234 synthesizes a new lipopolysaccharide (LPS), characterized by a rhamnan O-antigen. The presence of this rhamnose-rich LPS is important for the establishment of competent symbiotic interactions between NGR234 and many species of leguminous plants. Two putative rhamnosyl transferases are encoded in a cluster of genes previously shown to be necessary for the synthesis of the rhamnose-rich LPS. These two genes, wbgA and rgpF, were mutated. The resulting mutant strains synthesized truncated rough LPS species rather than the wild-type rhamnose-rich LPS when grown with flavonoids. Based on the compositions of these purified mutant LPS species, we inferred that RgpF is responsible for adding the first one to three rhamnose residues to the flavonoid-induced LPS, whereas WbgA is necessary for the synthesis of the rest of the rhamnan O-antigen. The NGR234 homologue of lpsB, which, in other bacteria, encodes a glycosyl transferase acting early in synthesis of the core portion of LPS, was identified and also mutated. LpsB was required for all the LPS species produced by NGR234, in the presence or absence of flavonoids. Mutants (i.e., of lpsB and rgpF) that lacked any portion of the rhamnan O-antigen of the induced LPS were severely affected in their symbiotic interaction with Vigna unguiculata, whereas the NGRΩwbgA mutant, although having very few rhamnose residues in its LPS, was able to elicit functional nodules.

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