Effect of anntrCmutation on amino acid or urea utilization and on nitrogenase switch-off inHerbaspirillum seropedicae

2008 ◽  
Vol 54 (3) ◽  
pp. 235-239 ◽  
Author(s):  
Claudio L. Gusso ◽  
Emanuel M. de Souza ◽  
Liu Un Rigo ◽  
Fábio de Oliveira Pedrosa ◽  
M.G. Yates ◽  
...  
Keyword(s):  
Ammonium Chloride ◽  
Type Strain ◽  
Wild Type Strain ◽  
Nitrogenase Activity ◽  
Nitrogen Sources ◽  
Effective Inhibitor ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Herbaspirillum Seropedicae ◽  
Nitrogenase Inhibition

Herbaspirillum seropedicae is a nitrogen-fixing bacterium that grows well with ammonium chloride or sodium nitrate as alternative single nitrogen sources but that grows more slowly with l-alanine, l-serine, l-proline, or urea. The ntrC mutant strain DCP286A was able to utilize only ammonium or urea of these nitrogen sources. The addition of 1 mmol·L–1ammonium chloride to the nitrogen-fixing wild-type strain inhibited nitrogenase activity rapidly and completely. Urea was a less effective inhibitor; approximately 20% of nitrogenase activity remained 40 min after the addition of 1 mmol·L–1urea. The effect of the ntrC mutation on nitrogenase inhibition (switch-off) was studied in strain DCP286A containing the constitutively expressed gene nifA of H. seropedicae. In this strain, nitrogenase inhibition by ammonium was completely abolished, but the addition of urea produced a reduction in nitrogenase activity similar to that of the wild-type strain. The results suggest that the NtrC protein is required for assimilation of nitrate and the tested amino acids by H. seropedicae. Furthermore, NtrC is also necessary for ammonium-induced switch-off of nitrogenase but is not involved in the mechanism of nitrogenase switch-off by urea.

scholarly journals Regulation of nitrate reductase of Neurospora at the level of transcription and translation

1973 ◽  
Vol 134 (3) ◽  
pp. 673-685 ◽  
Author(s):  
G. J. Sorger ◽  
J. Davies
Keyword(s):  
Nitrate Reductase ◽  
Type Strain ◽  
Wild Type Strain ◽  
Reductase Activity ◽  
Nitrogen Sources ◽  
Normal Strain ◽  
Wild Type ◽  
Benzyl Viologen ◽  
In The Wild ◽  
Partial Activity

The presence of nitrate is required for the induced synthesis of NADPH–nitrate reductase and its related partial activity Benzyl Viologen–nitrate reductase in a wild-type strain of Neurospora. In nit-3, a mutant lacking complete NADPH–nitrate reductase activity but retaining the partial activity Benzyl Viologen–nitrate reductase, the presence of nitrate ions is not required for the de-repressed synthesis of the latter enzyme. The accumulation of the capacity to synthesize nitrate reductase, and the related Benzyl Viologen–nitrate reductase, in the absence of protein synthesis does not require nitrate in the normal strain or in strain nit-3. Ammonia antagonizes the accumulation of this capacity in both strains. Nitrate is required for the synthesis of nitrate reductase and related activities from presumedly preformed mRNA in the wild-type strain. Nitrate is not required for the comparable function in strain nit-3. Ammonia appears to stop the synthesis of nitrate reductase and related activities from presumedly preformed mRNA in the wild-type strain and in strain nit-3. The effects of nitrate, or ammonia and of no nitrogen source on the induced synthesis of nitrate reductase cannot be explained on the basis of the effects of the different nitrogen sources on general synthesis of RNA or of protein.

Short-Term Regulation of Nitrogenase Activity by NH4+ in Rhodobacter capsulatus: Multiple In Vivo Nitrogenase Responses to NH4+ Addition

1998 ◽  
Vol 180 (23) ◽  
pp. 6392-6395 ◽  
Author(s):  
Alexander F. Yakunin ◽  
Patrick C. Hallenbeck
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Photosynthetic Bacterium ◽  
Wild Type ◽  
Magnitude Response ◽  
Short Term ◽  
Reversible Inhibition

ABSTRACT The photosynthetic bacterium Rhodobacter capsulatus has been shown to carry out nitrogenase “switch-off,” a rapid, reversible inhibition of in vivo activity. Here, we demonstrate that highly nitrogen-limited cultures of both the wild-type strain and adraT draG mutant are capable of nitrogenase switch-off while moderately nitrogen-limited cultures show instead a “magnitude” response, with a decrease in in vivo nitrogenase activity that is proportional to the amount of added NH4 +.

scholarly journals Functional Analysis of Fructosyl-Amino Acid Oxidases of Aspergillus oryzae

2004 ◽  
Vol 70 (10) ◽  
pp. 5882-5890 ◽  
Author(s):  
Shin-ichi Akazawa ◽  
Tetsuya Karino ◽  
Nobuyuki Yoshida ◽  
Tohoru Katsuragi ◽  
Yoshiki Tani
Keyword(s):  
Amino Acid ◽  
Aspergillus Oryzae ◽  
Type Strain ◽  
Wild Type Strain ◽  
Nitrogen Sources ◽  
Amino Acid Sequences ◽  
Wild Type ◽  
Amino Acid Oxidase ◽  
Carbon And Nitrogen Sources ◽  
Carbon And Nitrogen

ABSTRACT Three active fractions of fructosyl-amino acid oxidase (FAOD-Ao1, -Ao2a, and -Ao2b) were isolated from Aspergillus oryzae strain RIB40. N-terminal and internal amino acid sequences of FAOD-Ao2a corresponded to those of FAOD-Ao2b, suggesting that these two isozymes were derived from the same protein. FAOD-Ao1 and -Ao2 were different in substrate specificity and subunit assembly; FAOD-Ao2 was active toward N ε-fructosyl N α-Z-lysine and fructosyl valine (Fru-Val), whereas FAOD-Ao1 was not active toward Fru-Val. The genes encoding the FAOD isozymes (i.e., FAOAo1 and FAOAo2) were cloned by PCR with an FAOD-specific primer set. The deduced amino acid sequences revealed that FAOD-Ao1 was 50% identical to FAOD-Ao2, and each isozyme had a peroxisome-targeting signal-1, indicating their localization in peroxisomes. The genes was expressed in Escherichia coli and rFaoAo2 showed the same characteristics as FAOD-Ao2, whereas rFaoAo1 was not active. FAOAo2 disruptant was obtained by using ptrA as a selective marker. Wild-type strain grew on the medium containing Fru-Val as the sole carbon and nitrogen sources, but strain ΔfaoAo2 did not grow. Addition of glucose or (NH4)2SO4 to the Fru-Val medium did not affect the assimilation of Fru-Val by wild-type, indicating glucose and ammonium repressions did not occur in the expression of the FAOAo2 gene. Furthermore, conidia of the wild-type strain did not germinate on the medium containing Fru-Val and NaNO2 as the sole carbon and nitrogen sources, respectively, suggesting that Fru-Val may also repress gene expression of nitrite reductase. These results indicated that FAOD is needed for utilization of fructosyl-amino acids as nitrogen sources in A. oryzae.

scholarly journals Enhanced Nitrogen Fixation in a glgX-Deficient Strain of Cyanothece sp. Strain ATCC 51142, a Unicellular Nitrogen-Fixing Cyanobacterium

2019 ◽  
Vol 85 (7) ◽  
Author(s):  
Michelle Liberton ◽  
Anindita Bandyopadhyay ◽  
Himadri B. Pakrasi
Keyword(s):  
Nitrogen Fixation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Light Period ◽  
Strain Atcc ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Modification System ◽  
Carbon And Nitrogen ◽  
Global Carbon

ABSTRACT Cyanobacteria are oxygenic photosynthetic prokaryotes with important roles in the global carbon and nitrogen cycles. Unicellular nitrogen-fixing cyanobacteria are known to be ubiquitous, contributing to the nitrogen budget in diverse ecosystems. In the unicellular cyanobacterium Cyanothece sp. strain ATCC 51142, carbon assimilation and carbohydrate storage are crucial processes that occur as part of a robust diurnal cycle of photosynthesis and nitrogen fixation. During the light period, cells accumulate fixed carbon in glycogen granules to use as stored energy to power nitrogen fixation in the dark. These processes have not been thoroughly investigated, due to the lack of a genetic modification system in this organism. In bacterial glycogen metabolism, the glgX gene encodes a debranching enzyme that functions in storage polysaccharide catabolism. To probe the consequences of modifying the cycle of glycogen accumulation and subsequent mobilization, we engineered a strain of Cyanothece 51142 in which the glgX gene was genetically disrupted. We found that the ΔglgX strain exhibited a higher growth rate than the wild-type strain and displayed a higher rate of nitrogen fixation. Glycogen accumulated to higher levels at the end of the light period in the ΔglgX strain, compared to the wild-type strain. These data suggest that the larger glycogen pool maintained by the ΔglgX mutant is able to fuel greater growth and nitrogen fixation ability. IMPORTANCE Cyanobacteria are oxygenic photosynthetic bacteria that are found in a wide variety of ecological environments, where they are important contributors to global carbon and nitrogen cycles. Genetic manipulation systems have been developed in a number of cyanobacterial strains, allowing both the interruption of endogenous genes and the introduction of new genes and entire pathways. However, unicellular diazotrophic cyanobacteria have been generally recalcitrant to genetic transformation. These cyanobacteria are becoming important model systems to study diurnally regulated processes. Strains of the Cyanothece genus have been characterized as displaying robust growth and high rates of nitrogen fixation. The significance of our study is in the establishment of a genetic modification system in a unicellular diazotrophic cyanobacterium, the demonstration of the interruption of the glgX gene in Cyanothece sp. strain ATCC 51142, and the characterization of the increased nitrogen-fixing ability of this strain.

scholarly journals Two New Sinorhizobium meliloti LysR-Type Transcriptional Regulators Required for Nodulation

2005 ◽  
Vol 187 (13) ◽  
pp. 4562-4572 ◽  
Author(s):  
Li Luo ◽  
Shi-Yi Yao ◽  
Anke Becker ◽  
Silvia Rüberg ◽  
Guan-Qiao Yu ◽  
...  
Keyword(s):  
Cell Growth ◽  
Type Strain ◽  
Sinorhizobium Meliloti ◽  
Wild Type Strain ◽  
Nitrogenase Activity ◽  
Transcriptional Regulators ◽  
Wild Type ◽  
Free Living ◽  
Multiple Points ◽  
Regulator Genes

ABSTRACT The establishment of an effective nitrogen-fixing symbiosis between Sinorhizobium meliloti and its legume host alfalfa (Medicago sativa) depends on the timely expression of nodulation genes that are controlled by LysR-type regulators. Ninety putative genes coding for LysR-type transcriptional regulators were identified in the recently sequenced S. meliloti genome. All 90 putative lysR genes were mutagenized using plasmid insertions as a first step toward determining their roles in symbiosis. Two new LysR-type symbiosis regulator genes, lsrA and lsrB, were identified in the screening. Both the lsrA and lsrB genes are expressed in free-living S. meliloti cells, but they are not required for cell growth. An lsrA1 mutant was defective in symbiosis and elicited only white nodules that exhibited no nitrogenase activity. Cells of the lsrA1 mutant were recovered from the white nodules, suggesting that the lsrA1 mutant was blocked early in nodulation. An lsrB1 mutant was deficient in symbiosis and elicited a mixture of pink and white nodules on alfalfa plants. These plants exhibited lower overall nitrogenase activity than plants inoculated with the wild-type strain, which is consistent with the fact that most of the alfalfa plants inoculated with the lsrB1 mutant were short and yellow. Cells of the lsrB1 mutant were recovered from both pink and white nodules, suggesting that lsrB1 mutants could be blocked at multiple points during nodulation. The identification of two new LysR-type symbiosis transcriptional regulators provides two new avenues for understanding the complex S. meliloti-alfalfa interactions which occur during symbiosis.

scholarly journals A Chemotaxis Receptor Modulates Nodulation during the Azorhizobium caulinodans-Sesbania rostrata Symbiosis

2016 ◽  
Vol 82 (11) ◽  
pp. 3174-3184 ◽  
Author(s):  
Nan Jiang ◽  
Wei Liu ◽  
Yan Li ◽  
Hailong Wu ◽  
Zhenhai Zhang ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Bacterial Chemotaxis ◽  
Sesbania Rostrata ◽  
Nitrogen Fixing ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Free Living ◽  
Content Type

ABSTRACTAzorhizobium caulinodansORS571 is a free-living nitrogen-fixing bacterium which can induce nitrogen-fixing nodules both on the root and the stem of its legume hostSesbania rostrata. This bacterium, which is an obligate aerobe that moves by means of a polar flagellum, possesses a single chemotaxis signal transduction pathway. The objective of this work was to examine the role that chemotaxis and aerotaxis play in the lifestyle of the bacterium in free-living and symbiotic conditions. In bacterial chemotaxis, chemoreceptors sense environmental changes and transmit this information to the chemotactic machinery to guide motile bacteria to preferred niches. Here, we characterized a chemoreceptor ofA. caulinodanscontaining an N-terminal PAS domain, named IcpB. IcpB is a soluble heme-binding protein that localized at the cell poles. AnicpBmutant strain was impaired in sensing oxygen gradients and in chemotaxis response to organic acids. Compared to the wild-type strain, theicpBmutant strain was also affected in the production of extracellular polysaccharides and impaired in flocculation. When inoculated alone, theicpBmutant induced nodules onS. rostrata, but the nodules formed were smaller and had reduced N2-fixing activity. TheicpBmutant failed to nodulate its host when inoculated competitively with the wild-type strain. Together, the results identify chemotaxis and sensing of oxygen by IcpB as key regulators of theA. caulinodans-S. rostratasymbiosis.IMPORTANCEBacterial chemotaxis has been implicated in the establishment of various plant-microbe associations, including that of rhizobial symbionts with their legume host. The exact signal(s) detected by the motile bacteria that guide them to their plant hosts remain poorly characterized.Azorhizobium caulinodansORS571 is a diazotroph that is a motile and chemotactic rhizobial symbiont ofSesbania rostrata, where it forms nitrogen-fixing nodules on both the roots and the stems of the legume host. We identify here a chemotaxis receptor sensing oxygen inA. caulinodansthat is critical for nodulation and nitrogen fixation on the stems and roots ofS. rostrata. These results identify oxygen sensing and chemotaxis as key regulators of theA. caulinodans-S. rostratasymbiosis.

scholarly journals Regulation of Expression of GLT1, the Gene Encoding Glutamate Synthase in Saccharomyces cerevisiae

1998 ◽  
Vol 180 (14) ◽  
pp. 3533-3540 ◽  
Author(s):  
Lourdes Valenzuela ◽  
Paola Ballario ◽  
Cristina Aranda ◽  
Patrizia Filetici ◽  
Alicia González
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcriptional Regulation ◽  
Dna Sequences ◽  
Transcriptional Activation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Glutamate Synthase ◽  
Nitrogen Sources ◽  
Wild Type ◽  
Regulation Of Expression

ABSTRACT Saccharomyces cerevisiae glutamate synthase (GOGAT) is an oligomeric enzyme composed of three 199-kDa identical subunits encoded by GLT1. In this work, we analyzed GLT1transcriptional regulation. GLT1-lacZ fusions were prepared and GLT1 expression was determined in a GDH1wild-type strain and in a gdh1 mutant derivative grown in the presence of various nitrogen sources. Null mutants impaired inGCN4, GLN3, GAT1/NIL1, orUGA43/DAL80 were transformed with a GLT1-lacZfusion to determine whether the above-mentioned transcriptional factors had a role in GLT1 expression. A collection of increasingly larger 5′ deletion derivatives of the GLT1 promoter was constructed to identify DNA sequences that could be involved inGLT1 transcriptional regulation. The effect of the lack ofGCN4, GLN3, or GAT1/NIL1 was also tested in the pertinent 5′ deletion derivatives. Our results indicate that (i) GLT1 expression is negatively modulated by glutamate-mediated repression and positively regulated by Gln3p- and Gcn4p-dependent transcriptional activation; (ii) twocis-acting elements, a CGGN15CCG palindrome and an imperfect poly(dA-dT), are present and could play a role inGLT1 transcriptional activation; and (iii) GLT1expression is moderately regulated by GCN4 under amino acid deprivation. Our results suggest that in a wild-type strain grown on ammonium, GOGAT constitutes an ancillary pathway for glutamate biosynthesis.

scholarly journals Effects of Mutations of RAD50, RAD51, RAD52, and Related Genes on Illegitimate Recombination in Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 142 (2) ◽  
pp. 383-391 ◽  
Author(s):  
Yasumasa Tsukamoto ◽  
Jun-ichi Kato ◽  
Hideo Ikeda
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Quantitative Analysis ◽  
Structural Analysis ◽  
Recombination Rate ◽  
Type Strain ◽  
Negative Selection ◽  
Wild Type Strain ◽  
Illegitimate Recombination ◽  
Wild Type ◽  
In The Wild

Abstract To examine the mechanism of illegitimate recombination in Saccharomyces cerevisiae, we have developed a plasmid system for quantitative analysis of deletion formation. A can1 cyh2 cell carrying two negative selection markers, the CAN1 and CYH2 genes, on a YCp plasmid is sensitive to canavanine and cycloheximide, but the cell becomes resistant to both drugs when the plasmid has a deletion over the CAN1 and CYH2 genes. Structural analysis of the recombinant plasmids obtained from the resistant cells showed that the plasmids had deletions at various sites of the CAN1-CYH2 region and there were only short regions of homology (1-5 bp) at the recombination junctions. The results indicated that the deletion detected in this system were formed by illegitimate recombination. Study on the effect of several rad mutations showed that the recombination rate was reduced by 30-, 10-, 10-, and 10-fold in the rad52, rad50, mre11, and xrs2 mutants, respectively, while in the rud51, 54, 55, and 57 mutants, the rate was comparable to that in the wild-type strain. The rad52 mutation did not affect length of homology at junction sites of illegitimate recombination.

scholarly journals The role of Zur-regulated lipoprotein A in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles in Acinetobacter baumannii

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nayeong Kim ◽  
Hyo Jeong Kim ◽  
Man Hwan Oh ◽  
Se Yeon Kim ◽  
Mi Hyun Kim ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Mutant Strain ◽  
Antimicrobial Susceptibility ◽  
Type Strain ◽  
Wild Type Strain ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Wild Type ◽  
Bacterial Morphology

Abstract Background Zinc uptake-regulator (Zur)-regulated lipoprotein A (ZrlA) plays a role in bacterial fitness and overcoming antimicrobial exposure in Acinetobacter baumannii. This study further characterized the zrlA gene and its encoded protein and investigated the roles of the zrlA gene in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles (OMVs) in A. baumannii ATCC 17978. Results In silico and polymerase chain reaction analyses showed that the zrlA gene was conserved among A. baumannii strains with 97–100% sequence homology. Recombinant ZrlA protein exhibited a specific enzymatic activity of D-alanine-D-alanine carboxypeptidase. Wild-type A. baumannii exhibited more morphological heterogeneity than a ΔzrlA mutant strain during stationary phase. The ΔzrlA mutant strain was more susceptible to gentamicin than the wild-type strain. Sizes and protein profiles of OMVs were similar between the wild-type and ΔzrlA mutant strains, but the ΔzrlA mutant strain produced 9.7 times more OMV particles than the wild-type strain. OMVs from the ΔzrlA mutant were more cytotoxic in cultured epithelial cells than OMVs from the wild-type strain. Conclusions The present study demonstrated that A. baumannii ZrlA contributes to bacterial morphogenesis and antimicrobial resistance, but its deletion increases OMV production and OMV-mediated host cell cytotoxicity.

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