Excretion of ammonium by Azospirillum brasilense mutants resistant to ethylenediamine

1991 ◽  
Vol 37 (7) ◽  
pp. 549-553 ◽  
Author(s):  
H. B. Machado ◽  
S. Funayama ◽  
L. U. Rigo ◽  
F. O. Pedrosa
Keyword(s):  
Glutamine Synthetase ◽  
Azospirillum Brasilense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Synthetase Activity ◽  
Ammonium Excretion ◽  
Glutamine Synthetase Activity ◽  
Wild Type ◽  
High Concentration ◽  
Low Levels

Several spontaneous ethylenediamine-resistant mutants of Azospirillum brasilense strain FP2 (Sp7, NalR SmR) were isolated. Four mutants, HM053, HM14, HM26, and HM210, were found to fix nitrogen constitutively in the presence of high concentration of NH4+ and to excrete NH4+ derived from nitrogen fixation. They also showed lower rates of NH4+ uptake than the wild-type strain, FP2. All of the mutants were prototrophic for glutamine or glutamate. Their glutamate synthase and glutamate dehydrogenase activities were similar to those of the wild-type strain. However, they presented different patterns of glutamine synthetase activity. Mutant HM14 showed low levels of normally regulated glutamine synthetase activity, while the other mutants showed low levels (HM053) or wild-type levels (HM26 and HM210) of constitutively adenylylated glutamine synthetase activity. The mutants are probably defective in the adenylylation system. Key words: Azospirillum brasilense, ammonium excretion, ethylenediamine resistance, glutamine synthetase.

scholarly journals Expression and function of the cdgD gene, encoding a CHASE–PAS-DGC-EAL domain protein, in Azospirillum brasilense

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Francisco Cruz-Pérez ◽  
Roxana Lara-Oueilhe ◽  
Cynthia Marcos-Jiménez ◽  
Ricardo Cuatlayotl-Olarte ◽  
María Luisa Xiqui-Vázquez ◽  
...  
Keyword(s):  
Azospirillum Brasilense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Soil Conditions ◽  
Wild Type ◽  
Gene Encoding ◽  
Wheat Roots ◽  
Genes Encoding ◽  
In The Wild ◽  
Plant Growth Promoting

AbstractThe plant growth-promoting bacterium Azospirillum brasilense contains several genes encoding proteins involved in the biosynthesis and degradation of the second messenger cyclic-di-GMP, which may control key bacterial functions, such as biofilm formation and motility. Here, we analysed the function and expression of the cdgD gene, encoding a multidomain protein that includes GGDEF-EAL domains and CHASE and PAS domains. An insertional cdgD gene mutant was constructed, and analysis of biofilm and extracellular polymeric substance production, as well as the motility phenotype indicated that cdgD encoded a functional diguanylate protein. These results were correlated with a reduced overall cellular concentration of cyclic-di-GMP in the mutant over 48 h compared with that observed in the wild-type strain, which was recovered in the complemented strain. In addition, cdgD gene expression was measured in cells growing under planktonic or biofilm conditions, and differential expression was observed when KNO3 or NH4Cl was added to the minimal medium as a nitrogen source. The transcriptional fusion of the cdgD promoter with the gene encoding the autofluorescent mCherry protein indicated that the cdgD gene was expressed both under abiotic conditions and in association with wheat roots. Reduced colonization of wheat roots was observed for the mutant compared with the wild-type strain grown in the same soil conditions. The Azospirillum-plant association begins with the motility of the bacterium towards the plant rhizosphere followed by the adsorption and adherence of these bacteria to plant roots. Therefore, it is important to study the genes that contribute to this initial interaction of the bacterium with its host plant.

scholarly journals Complementation of the yeast deletion mutant DeltaNCE103 by members of the beta class of carbonic anhydrases is dependent on carbonic anhydrase activity rather than on antioxidant activity

2004 ◽  
Vol 379 (3) ◽  
pp. 609-615 ◽  
Author(s):  
Daniel CLARK ◽  
Roger S. ROWLETT ◽  
John R. COLEMAN ◽  
Daniel F. KLESSIG
Keyword(s):  
Antioxidant Activity ◽  
Type Strain ◽  
Deletion Mutant ◽  
Wild Type Strain ◽  
Carbonic Anhydrase Activity ◽  
Site Directed Mutagenesis ◽  
Carbonic Anhydrases ◽  
Wild Type ◽  
Tobacco Chloroplast ◽  
Low Levels

In recent years, members of the β class of CAs (carbonic anhydrases) have been shown to complement ΔNCE103, a yeast strain unable to grow under aerobic conditions. The activity required for complementation of ΔNCE103 by tobacco chloroplast CA was studied by site-directed mutagenesis. E196A (Glu196→Ala), a mutated tobacco CA with low levels of CA activity, complemented ΔNCE103. To determine whether restoration of ΔNCE103 was due to residual levels of CA activity or whether it was related to previously proposed antioxidant activity of CAs [Götz, Gnann and Zimmermann (1999) Yeast 15, 855–864], additional complementation analysis was performed using human CAII, an α CA structurally unrelated to the β class of CAs to which the tobacco protein belongs. Human CAII complemented ΔNCE103, strongly arguing that CA activity is responsible for the complementation of ΔNCE103. Consistent with this conclusion, recombinant NCE103 synthesized in Escherichia coli shows CA activity, and ΔNCE103 expressing the tobacco chloroplast CA exhibits the same sensitivity to H2O2 as the wild-type strain.

scholarly journals Involvement of the Reserve Material Poly-β-Hydroxybutyrate in Azospirillum brasilense Stress Endurance and Root Colonization

2003 ◽  
Vol 69 (6) ◽  
pp. 3244-3250 ◽  
Author(s):  
Daniel Kadouri ◽  
Edouard Jurkevitch ◽  
Yaacov Okon
Keyword(s):  
Plant Growth ◽  
Mutant Strain ◽  
Azospirillum Brasilense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Root Colonization ◽  
Cell Aggregation ◽  
Wild Type ◽  
Phb Production ◽  
Promote Plant Growth

ABSTRACT When grown under suboptimal conditions, rhizobacteria of the genus Azospirillum produce high levels of poly-β-hydroxybutyrate (PHB). Azospirillum brasilense strain Sp7 and a phbC (PHB synthase) mutant strain in which PHB production is impaired were evaluated for metabolic versatility, for the ability to endure various stress conditions, for survival in soil inoculants, and for the potential to promote plant growth. The carbon source utilization data were similar for the wild-type and mutant strains, but the generation time of the wild-type strain was shorter than that of the mutant strain with all carbon sources tested. The ability of the wild type to endure UV irradiation, heat, osmotic pressure, osmotic shock, and desiccation and to grow in the presence of hydrogen peroxide was greater than that of the mutant strain. The motility and cell aggregation of the mutant strain were greater than the motility and cell aggregation of the wild type. However, the wild type exhibited greater chemotactic responses towards attractants than the mutant strain exhibited. The wild-type strain exhibited better survival than the mutant strain in carrier materials used for soil inoculants, but no difference in the ability to promote plant growth was detected between the strains. In soil, the two strains colonized roots to the same extent. It appears that synthesis and utilization of PHB as a carbon and energy source by A. brasilense under stress conditions favor establishment of this bacterium and its survival in competitive environments. However, in A. brasilense, PHB production does not seem to provide an advantage in root colonization under the conditions tested.

scholarly journals Development of Mutants of Coniothyrium Minitans with Improved Efficiency for Control of Sclerotinia Sclerotiorum

2011 ◽  
Vol 51 (2) ◽  
pp. 179-183 ◽  
Author(s):  
Itamar Melo ◽  
Alex Moretini ◽  
Ana Cassiolato ◽  
Jane Faull
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Plant Tissue ◽  
Type Strain ◽  
Mycelial Growth ◽  
Wild Type Strain ◽  
Wild Type ◽  
Coniothyrium Minitans ◽  
High Concentration ◽  
Mutant Strains ◽  
Chitinase Production

Development of Mutants ofConiothyrium Minitanswith Improved Efficiency for Control ofSclerotinia SclerotiorumConiothyrium minitans(CM) is hyperparasitic toSclerotinia sclerotiorum(SS), a pathogen of many economically important crops. In this paper, we describe the isolation of improved mutants of CM, using a UV - irradiation regime, with altered chitinase production and tolerance to high concentration of iprodione, which are effective against SS. Three out of the 59 mutants obtained inhibited the mycelial growth of CM. Infectivity of sclerotia by the new mutants was assayed by the plant-tissue-based system using carrot segments. More than 80% of sclerotia were colonized by the mutants and the wild-type CM. The mutant strains retained ability to produce significant amounts of chitinase. The mutants differed from their wild-type strain in appearance, morphology and sporulation. In conclusion, the results presented here provide evidence that the new biotypes ofC. minitansare effective in controllingS. sclerotiorum.

scholarly journals MtaR, a Regulator of Methionine Transport, Is Critical for Survival of Group B Streptococcus In Vivo

2003 ◽  
Vol 185 (22) ◽  
pp. 6592-6599 ◽  
Author(s):  
Daniel Shelver ◽  
Lakshmi Rajagopal ◽  
Theresa O. Harris ◽  
Craig E. Rubens
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
De Novo ◽  
Group B Streptococcus ◽  
Neonatal Rat ◽  
Wild Type ◽  
High Concentration ◽  
Group B ◽  
Methionine Transport

ABSTRACT The group B streptococcus (GBS) is an important human pathogen that infects newborns as well as adults. GBS also provides a model system for studying adaptation to different host environments due to its ability to survive in a variety of sites within the host. In this study, we have characterized a transcription factor, MtaR, that is essential for the ability of GBS to survive in vivo. An isogenic strain bearing a kanamycin insertion in mtaR was attenuated for survival in a neonatal-rat model of sepsis. The mtaR mutant grew poorly in human plasma, suggesting that its utilization of plasma-derived nutrients was inefficient. When an excess of exogenous methionine (200 μg/ml) was provided to the mtaR mutant, its growth rate in plasma was restored to that of the wild-type strain. The mtaR mutant grew poorly in chemically defined medium (CDM) prepared with methionine at a concentration similar to that of plasma (4 μg/ml) but was able to grow normally in CDM prepared with a high concentration of methionine (400 μg/ml). Both the wild-type strain and the mtaR mutant were incapable of growth in CDM lacking methionine, indicating that GBS cannot synthesize methionine de novo. When the abilities of the strains to incorporate radiolabeled methionine were compared, the mtaR mutant incorporated fivefold less methionine than the wild-type strain during a 10-min period. Collectively, the results from this study suggest that the ability to regulate expression of a methionine transport system is critical for GBS survival in vivo.

scholarly journals CebR as a Master Regulator for Cellulose/Cellooligosaccharide Catabolism Affects Morphological Development in Streptomyces griseus

2009 ◽  
Vol 191 (19) ◽  
pp. 5930-5940 ◽  
Author(s):  
Kazuya Marushima ◽  
Yasuo Ohnishi ◽  
Sueharu Horinouchi
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Glucose Repression ◽  
Streptomyces Griseus ◽  
Morphological Development ◽  
Galactosidase Activity ◽  
Wild Type ◽  
High Concentration ◽  
Master Regulator ◽  
In The Wild

ABSTRACT Streptomyces griseus mutants exhibiting deficient glucose repression of β-galactosidase activity on lactose-containing minimal medium supplemented with a high concentration of glucose were isolated. One of these mutants had a 12-bp deletion in cebR, which encodes a LacI/GalR family regulator. Disruption of cebR in the wild-type strain caused the same phenotype as the mutant, indicating that CebR is required for glucose repression of β-galactosidase activity. Recombinant CebR protein bound to a 14-bp inverted-repeat sequence (designated the CebR box) present in the promoter regions of cebR and the putative cellobiose utilization operon, cebEFG-bglC. The DNA-binding activity of CebR was impaired by cellooligosaccharides, including cellobiose, cellotriose, cellotetraose, cellopentaose, and cellohexaose. In agreement with this observation, transcription from the cebE and cebR promoters was greatly enhanced by the addition of cellobiose to the medium. Seven other genes containing one or two CebR boxes in their upstream regions were found in the S. griseus genome. Five of these genes encode putative secreted proteins: two cellulases, a cellulose-binding protein, a pectate lyase, and a protein of unknown function. These five genes and cebEFG-bglC were transcribed at levels 4 to 130 times higher in the ΔcebR mutant than in the wild-type strain, as determined by quantitative reverse transcription-PCR. These findings indicate that CebR is a master regulator of cellulose/cellooligosaccharide catabolism. Unexpectedly, the ΔcebR mutant formed very few aerial hyphae on lactose-containing medium, demonstrating a link between carbon source utilization and morphological development.

A RIBONUCLEIC ACID FRACTION OF NEUROSPORA CRASSA EVOKING DEVELOPMENT OF A PSEUDO-TRYPTOPHAN SYNTHETASE ACTIVITY BY EXTRACTS OF MUTANTS TD1, TD2, AND TD3

1965 ◽  
Vol 43 (11) ◽  
pp. 1813-1828 ◽  
Author(s):  
S. D. Wainwright ◽  
E. Sandra McFarlane
Keyword(s):  
Neurospora Crassa ◽  
Type Strain ◽  
Wild Type Strain ◽  
Enzymic Activity ◽  
Synthetase Activity ◽  
Acid Fraction ◽  
Wild Type ◽  
Mutant Strains ◽  
Tryptophan Synthetase

"Soluble RNA" fractions isolated from the wild-type strain of Neurospora crassa evoked development of a pseudo-tryptophan synthetase enzyme activity in vitro by extracts of mutant strains lacking ability to produce the enzymic activity. The RNA fractions contained no detectable "template RNA". Some properties of the component eliciting development of pseudo-tryptophan synthetase activity are reported.

scholarly journals ACTINOMYCIN-D ENHANCEMENT OF GLUTAMINE SYNTHETASE ACTIVITY IN CHICK EMBRYO RETINAS CULTURED IN THE PRESENCE OF CORTISOL

1971 ◽  
Vol 51 (1) ◽  
pp. 303-311 ◽  
Author(s):  
Liane Beif-Lehrer
Keyword(s):  
Chick Embryo ◽  
Glutamine Synthetase ◽  
Actinomycin D ◽  
Synthetase Activity ◽  
Control Mechanisms ◽  
Glutamine Synthetase Activity ◽  
Animal Cells ◽  
Low Levels

Cortisol can prematurely induce glutamine synthetase activity in the chick embryo retina. Under appropriate conditions, this effect can be enhanced by addition of low levels of actinomycin D; this enhancement is reversibly inhibited by cycloheximide. The magnitude of the effect is a function of time of exposure to hormone as well as antibiotic and is also a function of the age of the embryo; within the limits of the present study it did not appear to be a function of actinomycin-D concentration. The data are discussed in terms of current ideas of possible control mechanisms in animal cells.

scholarly journals glnE Is an Essential Gene inMycobacterium tuberculosis

2000 ◽  
Vol 182 (20) ◽  
pp. 5715-5720 ◽  
Author(s):  
Tanya Parish ◽  
Neil G. Stoker
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Glutamine Synthetase ◽  
Essential Gene ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Chromosomal Gene ◽  
Wild Type ◽  
Double Crossover ◽  
Functional Copy

ABSTRACT Mycobacterium tuberculosis possesses a homologue of glnE, potentially encoding a regulator of glutamine synthetase activity. We attempted to constructglnE-disrupted mutants using a two-step strategy, whereby a single-crossover strain was first isolated, followed bysacB counterselection to isolate the double-crossover strain. Of 192 sucrose-resistant colonies tested, none were mutants, although the wild-type double crossover could be easily isolated. When a second copy of the wild-type glnE was integrated into the chromosome, we could isolate both wild-type and mutant double-crossover strains. Thus, the chromosomal gene could only be replaced with a disrupted copy when another functional copy of the gene was provided, demonstrating that this gene is essential under the conditions tested.

scholarly journals Alkyl hydroperoxide reductase has a role in oxidative stress resistance and in modulating changes in cell-surface properties in Azospirillum brasilense Sp245

Microbiology ◽  
2009 ◽  
Vol 155 (4) ◽  
pp. 1192-1202 ◽  
Author(s):  
Mariam Wasim ◽  
Amber N. Bible ◽  
Zhihong Xie ◽  
Gladys Alexandre
Keyword(s):  
Oxidative Stress ◽  
Cell Surface ◽  
Surface Properties ◽  
Azospirillum Brasilense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Cell Aggregation ◽  
Wild Type ◽  
Cell Surface Properties ◽  
Alkyl Hydroperoxide

An ahpC mutant derivative of Azospirillum brasilense Sp245 (strain SK586) that encodes an alkyl hydroperoxide reductase was found to be more sensitive to oxidative stress caused by organic hydroperoxides compared with the wild-type. In addition, the ahpC mutant strain had multiple defects in a large array of cellular functions that were consistent with alteration of cell-surface properties, such as cell morphology in stationary phase, Calcofluor White-, Congo Red- and lectin-binding abilities, as well as cell-to-cell aggregation and flocculation. All phenotypes of the ahpC mutant were complemented by in trans expression of AhpC, and overexpression of AhpC in the wild-type strain was found to affect the same set of phenotypes, suggesting that the pleiotropic effects were caused by the ahpC mutation. SK586 was also found to be fully motile, but it lost motility at a higher rate than the wild-type during growth, such that most SK586 cells were non-motile in stationary phase. Despite these defects, the mutant did not differ from the wild-type in short-term colonization of sterile wheat roots when inoculated alone, and in competition with the wild-type strain; this implied that AhpC activity may not endow the cells with a competitive advantage in colonization under these conditions. Although the exact function of AhpC in affecting these phenotypes remains to be determined, changes in cell morphology, surface properties, cell-to-cell aggregation and flocculation are common adaptive responses to various stresses in bacteria, and the data obtained here suggest that AhpC contributes to modulating such stress responses in A. brasilense.

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