Oxygen tolerance of uptake hydrogenase in Azospirillum spp.

1986 ◽  
Vol 32 (12) ◽  
pp. 897-900 ◽  
Author(s):  
Changlin Fu ◽  
Roger Knowles
Keyword(s):  
Stationary Phase ◽  
Hydrogenase Activity ◽  
Uptake Hydrogenase ◽  
Azospirillum Lipoferum ◽  
Oxygen Tolerance ◽  
Fold Induction ◽  
Uptake Activity ◽  
Significant Uptake

Uptake hydrogenase in Azospirillum lipoferum and A. amazonense was studied in vivo under N2-fixing and NH4Cl-grown conditions. N2-flxing cultures of both A. lipoferum and A. amazonense showed significant uptake-hydrogenase activities which reached their maximum in late log phase, N2-fixing A. amazonense had 5 times higher H2 uptake activity than N2-fixing A. lipoferum. Uptake-hydrogenase activities of both species were negligible in NH4Cl-grown cells. However, sparging with H2 during growth caused over a 100-fold induction of uptake-hydrogenase activities, and prolonged the activities into stationary phase, suggesting that hydrogenase synthesis requires exogenous H2 as inducer. Oxygen-dependent uptake-hydrogenase activity in A. amazonense was almost unaffected by 20 kPa O2, whereas in A. lipoferum and A. brasilense activities were inhibited by 40 and 100%, respectively, in 20 kPa O2. Air caused a strong repression of hydrogenase synthesis in both species. Nitrogenase was roughly equally O2 sensitive in all three species.

scholarly journals EVALUATION OF HUP+, HUP– AND A TRANSCONJUGANT RHIZOBIUM ON YIELD, NITROGEN FIXATION, AND UPTAKE HYDROGENASE ACTIVITY IN SELECTED CHICKPEA CULTIVARS

HortScience ◽  
1996 ◽  
Vol 31 (3) ◽  
pp. 324e-324
Author(s):  
G.M. Sajid ◽  
W.F. Campbell
Keyword(s):  
Root Nodules ◽  
Hydrogen Uptake ◽  
Hydrogen Gas ◽  
Acetylene Reduction Activity ◽  
Hydrogenase Activity ◽  
Uptake Hydrogenase ◽  
Higher Plant ◽  
Reduction Activity ◽  
Uptake Activity ◽  
Plant Yields

Evolution of hydrogen gas (H2) during N2 reduction in root nodules results in inefficient use of energy needed for N2 fixation. Cultivars of chickpea (Cicer arietinum L.) were inoculated with Rhizobium strains with and without genes for uptake hydrogenase (Hup) activity. H2 evolution, acetylene reduction activity, and uptake hydrogenase (Hup) activity were assayed on the resulting nodules. The Hup– strains produced higher plant yields than the Hup+ strains. The +N controls produced significantly higher yields than the –N controls and plants inoculated with Rhizobium strains. Hydrogen uptake activity by Rhizobium strains was influenced by the cultivar characteristics. Expression of the plasmid-borne hup genes (pHU52) of Bradyrhizobium japonicum was modified by the host cultivar. The average nodule fresh weight and shoot and root dry weights of the cultivars significantly increased following inoculation with the transconjugant Hup+ Rhizobium strain. Thus, biological N2 fixation may be enhanced by selecting Rhizobium strains that are appropriately matched to the particular cultivar. Incorporation of transconjugant Hup+ genes can increase rhizobial activity.

Nitrogen fixation and hydrogen metabolism by Rhizobium leguminosarum isolates in pea root nodules

1981 ◽  
Vol 27 (10) ◽  
pp. 1028-1034 ◽  
Author(s):  
Louise M. Nelson ◽  
J. J. Child
Keyword(s):  
Relative Efficiency ◽  
Rhizobium Leguminosarum ◽  
High Efficiency ◽  
Root Nodules ◽  
Dry Weight ◽  
Hydrogenase Activity ◽  
Uptake Hydrogenase ◽  
Hydrogen Metabolism ◽  
N Content ◽  
Significant Uptake

A survey of 108 isolates of Rhizobium leguminosarum was conducted to determine the variation in H2 uptake and relative efficiency of N2 fixation in Pisum sativum L. root nodules and the relation of relative efficiency to plant dry weight and N content. Only 14 of the isolates exhibited significant uptake hydrogenase activity and none of these had sufficient hydrogenase activity to recycle all of the H2 produced by nitrogenase. In 74 of the isolates tested relative efficiencies of N2 fixation were less than 0.60.Twenty-nine of the isolates were ineffective, since total plant N at harvest did not differ significantly from uninoculated controls. The remaining 79 effective isolates could be divided into low-and high-efficiency groups. Plants which were inoculated with isolates from the two groups and harvested after 4 weeks did not differ significantly in plant dry weight or N content. Among the isolates with high relative efficiency of N2 fixation, two groups could be recognized: one possessing significant uptake hydrogenase activity, the other lacking hydrogenase activity but in which H2 evolution was low. Although the two groups did not differ with respect to plant dry weight or N content, the identification of this latter group may be of some significance for optimizing the efficiency of N2 fixation.

scholarly journals TMOD-15. EFFICACY OF THE MDM2 INHIBITOR KRT-232 IN GLIOBLASTOMA PATIENT-DERIVED XENOGRAFT MODELS

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii231-ii231
Author(s):  
Rachael Vaubel ◽  
Ann Mladek ◽  
Yu Zhao ◽  
Shiv K Gupta ◽  
Minjee Kim ◽  
...  
Keyword(s):  
Target Genes ◽  
Xenograft Model ◽  
Culture Conditions ◽  
Patient Derived Xenograft ◽  
Fold Induction ◽  
Extended Survival ◽  
Mdm2 Amplification ◽  
Mdm2 Inhibitor

Abstract Non-genotoxic reactivation of p53 by MDM2 inhibitors represents a promising therapeutic strategy for tumors with wild-type TP53, particularly tumors harboring MDM2 amplification. MDM2 controls p53 levels by targeting it for degradation, while disruption of the MDM2-p53 interaction causes rapid accumulation of p53 and activation of the p53 pathway. We examined the efficacy of the small molecule MDM2 inhibitor KRT-232, alone and in combination with radiation therapy (RT), in MDM2-amplified and/or p53 wildtype patient-derived xenograft (PDX) models of glioblastoma in vitro and in vivo. In vitro, glioblastoma PDX explant cultures showed sensitivity to KRT-232, both tumors with MDM2 amplification (GBM108 and G148) and non-amplified but TP53-wildtype lines (GBM10, GBM14, and GBM39), with IC50s ranging from 300-800 nM in FBS culture conditions. A TP53 p.F270C mutant PDX (GBM43) was inherently resistant, with IC50 >3000 nM. In the MDM2-amplified GBM108 line, KRT-232 led to a robust (5-6 fold) induction of p53-target genes p21, PUMA, and NOXA, with initiation of both apoptosis and senescence. Expression of p21 and PUMA was greater with KRT-232 in combination with RT (25-35 fold induction), while stable knock-down of p53 in GBM108 led to complete resistance to KRT-232. In contrast, GBM10 showed lower induction of p21 and PUMA (2-3 fold) and was more resistant to KRT-232. In an orthotopic GBM108 xenograft model, treatment with KRT-232 +/- RT for one week extended survival from 22 days (placebo) to 46 days (KRT-232 alone); combination KRT-232 + RT further extended survival (77 days) over RT alone (31 days). KRT-232 is an effective treatment in a subset of glioblastoma pre-clinical models alone and in combination with RT. Further studies are underway to understand the mechanisms conferring innate sensitivity or resistance to KRT-232.

scholarly journals Effects of Combination of Different −10 Hexamers and Downstream Sequences on Stationary-Phase-Specific Sigma Factor ςS-Dependent Transcription in Pseudomonas putida

2000 ◽  
Vol 182 (23) ◽  
pp. 6707-6713 ◽  
Author(s):  
Eve-Ly Ojangu ◽  
Andres Tover ◽  
Riho Teras ◽  
Maia Kivisaar
Keyword(s):  
Stationary Phase ◽  
Pseudomonas Putida ◽  
Sigma Factor ◽  
Sigma Factors ◽  
Deficient Mutant ◽  
Wild Type ◽  
In Vivo Experiments ◽  
Silent Genes ◽  
Rna Polymerase Holoenzyme

ABSTRACT The main sigma factor activating gene expression, necessary in stationary phase and under stress conditions, is ςS. In contrast to other minor sigma factors, RNA polymerase holoenzyme containing ςS (EςS) recognizes a number of promoters which are also recognized by that containing ς70 (Eς70). We have previously shown that transposon Tn4652 can activate silent genes in starvingPseudomonas putida cells by creating fusion promoters during transposition. The sequence of the fusion promoters is similar to the ς70-specific promoter consensus. The −10 hexameric sequence and the sequence downstream from the −10 element differ among these promoters. We found that transcription from the fusion promoters is stationary phase specific. Based on in vivo experiments carried out with wild-type and rpoS-deficient mutant P. putida, the effect of ςS on transcription from the fusion promoters was established only in some of these promoters. The importance of the sequence of the −10 hexamer has been pointed out in several published papers, but there is no information about whether the sequences downstream from the −10 element can affect ςS-dependent transcription. Combination of the −10 hexameric sequences and downstream sequences of different fusion promoters revealed that ςS-specific transcription from these promoters is not determined by the −10 hexameric sequence only. The results obtained in this study indicate that the sequence of the −10 element influences ςS-specific transcription in concert with the sequence downstream from the −10 box.

Monitoring of changes in the membrane proteome during stationary phase adaptation of Bacillus subtilis using in vivo labeling techniques

PROTEOMICS ◽  
2008 ◽  
Vol 8 (10) ◽  
pp. 2062-2076 ◽  
Author(s):  
Annette Dreisbach ◽  
Andreas Otto ◽  
Dörte Becher ◽  
Elke Hammer ◽  
Alexander Teumer ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Stationary Phase ◽  
Membrane Proteome ◽  
In Vivo Labeling

scholarly journals Individual Mycobacterium tuberculosis Resuscitation-Promoting Factor Homologues Are Dispensable for Growth In Vitro and In Vivo

2004 ◽  
Vol 72 (1) ◽  
pp. 515-526 ◽  
Author(s):  
JoAnn M. Tufariello ◽  
William R. Jacobs, ◽  
John Chan
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Stationary Phase ◽  
Essential Gene ◽  
Micrococcus Luteus ◽  
Expression Patterns ◽  
Active Growth ◽  
Prolonged Incubation ◽  
Aerosol Infection

ABSTRACT Mycobacterium tuberculosis possesses five genes with significant homology to the resuscitation-promoting factor (Rpf) of Micrococcus luteus. The M. luteus Rpf is a secreted ∼16-kDa protein which restores active growth to cultures of M. luteus rendered dormant by prolonged incubation in stationary phase. More recently, the Rpf-like proteins of M. tuberculosis have been shown to stimulate the growth of extended-stationary-phase cultures of Mycobacterium bovis BCG. These data suggest that the Rpf proteins can influence the growth of mycobacteria; however, the studies do not demonstrate specific functions for the various members of this protein family, nor do they assess the function of M. tuberculosis Rpf homologues in vivo. To address these questions, we have disrupted each of the five rpf-like genes in M. tuberculosis Erdman, and analyzed the mutants for their growth in vitro and in vivo. In contrast to M. luteus, for which rpf is an essential gene, we find that all of the M. tuberculosis rpf deletion mutant strains are viable; in addition, all show growth kinetics similar to Erdman wild type both in vitro and in mouse organs following aerosol infection. Analysis of rpf expression in M. tuberculosis cultures from early log phase through late stationary phase indicates that expression of the rpf-like genes is growth phase-dependent, and that the expression patterns of the five M. tuberculosis rpf genes, while overlapping to various degrees, are not uniform. We also provide evidence that mycobacterial rpf genes are expressed in vivo in the lungs of mice acutely infected with virulent M. tuberculosis.

scholarly journals Biodistribution and Tumor Uptake of 67Ga-Nimotuzumab in a Malignant Pleural Mesothelioma Xenograft

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3138 ◽  
Author(s):  
Vanessa Izquierdo-Sánchez ◽  
Saé Muñiz-Hernández ◽  
Héctor Vázquez-Becerra ◽  
Judith Pacheco-Yepez ◽  
Mario Romero-Piña ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Malignant Pleural Mesothelioma ◽  
Growth Factor Receptor ◽  
In Vivo Studies ◽  
Pleural Mesothelioma ◽  
Tumor Uptake ◽  
Epidermal Growth ◽  
Significant Uptake

Malignant pleural mesothelioma (MPM) is the most common tumor of the pulmonary pleura. It is a rare and aggressive malignancy, generally associated with continuous occupational exposure to asbestos. Only a multimodal-approach to treatment, based on surgical resection, chemotherapy and/or radiation, has shown some benefits. However, the survival rate remains low. Nimotuzumab (h-R3), an anti-EGFR (epidermal growth factor receptor) humanized antibody, is proposed as a promising agent for the treatment of MPM. The aim of this research was to implement a procedure for nimotuzumab radiolabeling to evaluate its biodistribution and affinity for EGF (epidermal growth factor) receptors present in a mesothelioma xenograft. Nimotuzumab was radiolabeled with 67Ga; radiolabel efficiency, radiochemical purity, serum stability, and biodistribution were evaluated. Biodistribution and tumor uptake imaging studies by microSPECT/CT in mesothelioma xenografts revealed constant nimotuzumab uptake at the tumor site during the first 48 h after drug administration. In vivo studies using MPM xenografts showed a significant uptake of this radioimmunoconjugate, which illustrates its potential as a biomarker that could promote its theranostic use in patients with MPM.

scholarly journals The l-Isoaspartyl Protein Repair Methyltransferase Enhances Survival of Aging Escherichia coli Subjected to Secondary Environmental Stresses

1998 ◽  
Vol 180 (10) ◽  
pp. 2623-2629 ◽  
Author(s):  
Jonathan E. Visick ◽  
Hui Cai ◽  
Steven Clarke
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Protein Denaturation ◽  
Environmental Stresses ◽  
Protein Repair ◽  
Repeated Heating ◽  
E Coli ◽  
Competitive Disadvantage ◽  
Biological World

ABSTRACT Like its homologs throughout the biological world, thel-isoaspartyl protein repair methyltransferase ofEscherichia coli, encoded by the pcm gene, can convert abnormal l-isoaspartyl residues in proteins (which form spontaneously from asparaginyl or aspartyl residues) to normal aspartyl residues. Mutations in pcm were reported to greatly reduce survival in stationary phase and when cells were subjected to heat or osmotic stresses (C. Li and S. Clarke, Proc. Natl. Acad. Sci. USA 89:9885–9889, 1992). However, we subsequently demonstrated that those strains had a secondary mutation inrpoS, which encodes a stationary-phase-specific sigma factor (J. E. Visick and S. Clarke, J. Bacteriol. 179:4158–4163, 1997). We now show that the rpoS mutation, resulting in a 90% decrease in HPII catalase activity, can account for the previously observed phenotypes. We further demonstrate that a new pcmmutant lacks these phenotypes. Interestingly, the newly constructedpcm mutant, when maintained in stationary phase for extended periods, is susceptible to environmental stresses, including exposure to methanol, oxygen radical generation by paraquat, high salt concentrations, and repeated heating to 42°C. The pcmmutation also results in a competitive disadvantage in stationary-phase cells. All of these phenotypes can be complemented by a functionalpcm gene integrated elsewhere in the chromosome. These data suggest that protein denaturation and isoaspartyl formation may act synergistically to the detriment of aging E. coli and that the repair methyltransferase can play a role in limiting the accumulation of the potentially disruptive isoaspartyl residues in vivo.

Regulation of the utilization of mRNA for eucaryotic elongation factor Tu in Friend erythroleukemia cells

1987 ◽  
Vol 7 (2) ◽  
pp. 687-697
Author(s):  
T R Rao ◽  
L I Slobin
Keyword(s):  
Stationary Phase ◽  
Elongation Factor ◽  
Fold Increase ◽  
Growth Conditions ◽  
Fresh Medium ◽  
Initiation Factor ◽  
Elongation Factor Tu ◽  
Erythroleukemia Cells ◽  
Friend Erythroleukemia Cells

When Friend erythroleukemia cells were allowed to grow to stationary phase (2 X 10(6) to 3 X 10(6) cells per ml), approximately 60% of the mRNA for eucaryotic elongation factor Tu (eEF-Tu) sedimented at less than or equal to 80S, and most of the remaining factor mRNA was associated with small polysomes. Under the same growth conditions, greater than 90% of the mRNA for eucaryotic initiation factor 4A remained associated with polysomes. The association of eEF-Tu mRNA with polysomes changed dramatically when stationary-phase cells were treated with fresh medium. After 1 h in fresh medium, approximately 90% of eEF-Tu mRNA in Friend cells was found in heavy polysomes. Associated with the shift of eEF-Tu mRNA into heavy polysomes, we found at least a 2.6-fold increase in the synthesis of eEF-Tu in vivo as well as a remarkable 40% decrease in the total amount of eEF-Tu mRNA per cell. Our data raise the possibility that eEF-Tu mRNA that has accumulated in ribonucleoprotein particles in stationary-phase cells is degraded rather than reutilized for eEF-Tu synthesis.

Hydrogen Evolution Catalyzed by Hydrogenase in Cultures of Cyanobacteria

1981 ◽  
Vol 36 (1-2) ◽  
pp. 87-92 ◽  
Author(s):  
Patrick C. Hallenbeck ◽  
Leon V. Kochian ◽  
John R. Benemann
Keyword(s):  
Hydrogen Production ◽  
Hydrogen Evolution ◽  
High Frequency ◽  
Nitrogenase Activity ◽  
Inhibitory Effect ◽  
Hydrogenase Activity ◽  
Oxygen Inhibition ◽  
Oxygen Sensitive

Abstract Cultures of Anabaena cylindrica, grown on media containing 5 mᴍ NH4Cl (which represses heterocyst formation), evolved hydrogen after a period of dark incubation under an argon atmosphere. This hydrogen production was not due to nitrogenase activity, which was nearly undetectable, but was due to a hydrogenase. Cultures grown on media with tungsten substituted for molybdenum had a high frequency of heterocysts (15%) and inactive nitrogenase after nitrogen starvation. The hydrogenase activity of these cultures was three-fold greater than the activity of non-heterocystous cultures. The effects of oxygen inhibition on hydrogen evolution by hetero-cystous cultures suggest that two pools of hydrogenase activity exist - an oxygen sensitive hydrogen evolution in vegetative cells and a relatively oxygen-resistent hydrogen evolution in heterocysts. In either case, inhibition by oxygen was reversible. Light had an inhibitory effect on net hydrogen evolution. Hydrogen production in vitro was much higher than in vivo, indicating that in vivo hydrogenase activity is limited by endogenous reductant supply.

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