scholarly journals Increased photoproduction of hydrogen by non-autotrophic mutants of Rhodopseudomonas capsulata

1984 ◽  
Vol 219 (2) ◽  
pp. 593-600 ◽  
Author(s):  
J C Willison ◽  
D Madern ◽  
P M Vignais
Keyword(s):  
Carbon Source ◽  
H2 Production ◽  
Rhodopseudomonas Capsulata ◽  
Hydrogenase Activity ◽  
Organic Substrates ◽  
Uptake Hydrogenase ◽  
Wild Type ◽  
Benzyl Viologen ◽  
In The Wild ◽  
Different Strains

Non-autotrophic (Aut -) mutants of Rhodopseudomonas capsulata B10 were tested for their efficiency of nitrogenase-mediated H2 production. Three of these mutants (IR3, IR4 and IR5) showed an increase stoichiometry of H2 production, mediated by nitrogenase, from certain organic substrates. For example, in a medium containing 7 mM-L-glutamate as nitrogen source, strain IR4 produced 10-20% more H2 than did the wild type with DL-lactate or L-malate as major carbon source, 20-50% more H2 with DL-malate, and up to 70% more with D-malate. Strain IR4 was deficient in ‘uptake’ hydrogenase activity as measured by H2-dependent reduction of Methylene Blue or Benzyl Viologen. However, this observation did not explain the increased efficiency of H2 production, since H2 uptake (H2 recycling) was undetectable in cells of the wild type. Instead, increased H2 production by the mutant appeared to be due to an improved conversion of organic substrates to H2 and CO2, presumably due to an altered carbon metabolism. The metabolism of D-malate by different strains was studied. An NAD+-dependent D-malic enzyme was synthesized constitutively by the wild type, and showed a Km for D-malate of 3 mM. The activity of this enzyme was approx. 50% higher in strain IR4 than in the wild type, and the mutant also grew twice as fast as the wild type with D-malate as sole carbon source.

Identification of genes required for hydrogenase activity in Chlamydomonas reinhardtii

2005 ◽  
Vol 33 (1) ◽  
pp. 102-104 ◽  
Author(s):  
M.C. Posewitz ◽  
P.W. King ◽  
S.L. Smolinski ◽  
R. Davis Smith ◽  
A.R. Ginley ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Green Alga ◽  
Transcriptional Response ◽  
H2 Production ◽  
Hydrogenase Activity ◽  
Wild Type ◽  
Anaerobic Conditions ◽  
H2 Photoproduction ◽  
H2 Sensor

The eukaryotic green alga, Chlamydomonas reinhardtii, produces H2 under anaerobic conditions, in a reaction catalysed by an [FeFe]-hydrogenase. To identify genes that influence H2 production in C. reinhardtii, a library of 6000 colonies on agar plates was screened with sensitive chemochromic H2-sensor films for clones defective in H2 production. Two mutants of particular interest were fully characterized. One mutant, hydEF-1, is unable to assemble an active [FeFe]-hydrogenase. This is the first reported C. reinhardtii mutant that is not capable of producing any H2. The second mutant, sta7-10, is not able to accumulate insoluble starch and has significantly lowered H2-photoproduction rates in comparison with the wild-type. In hydEF-1, anaerobiosis induces transcription of the two reported C. reinhardtii hydrogenase genes, HydA1 and HydA2, indicating a normal transcriptional response to anaerobiosis. In contrast, the transcription of both hydrogenase genes in sta7-10 is significantly attenuated.

Phosphatidylinositol phospholipase C mediates carbon sensing and vegetative nuclear duplication rates in Aspergillus nidulans

2011 ◽  
Vol 57 (7) ◽  
pp. 611-616 ◽  
Author(s):  
Ana Paula de Figueiredo Conte Vanzela ◽  
Suraia Said ◽  
Rolf Alexander Prade
Keyword(s):  
Molecular Weight ◽  
Carbon Source ◽  
Phospholipase C ◽  
Aspergillus Nidulans ◽  
Nuclear Division ◽  
Deficient Mutant ◽  
Wild Type ◽  
Pectinolytic Enzymes ◽  
In The Wild ◽  
Phosphatidylinositol Phospholipase C

In this work, we disrupted one of three putative phosphatidylinositol phospholipase C genes of Aspergillus nidulans and studied its effect on carbon source sensing linked to vegetative mitotic nuclear division. We showed that glucose does not affect nuclear division rates during early vegetative conidial germination (6–7 h) in either the wild type or the plcA-deficient mutant. Only after 8 h of cultivation on glucose did the mutant strain present some decrease in nuclear duplication. However, decreased nuclear division rates were observed in the wild type when cultivated in media amended with polypectate, whereas our plcA-deficient mutant did not show slow nuclear duplication rates when grown on this carbon source, even though it requires induction and secretion of multiple pectinolytic enzymes to be metabolized. Thus, plcA appears to be directly linked to high-molecular-weight carbon source sensing.

scholarly journals Reduction of cyclopropene by NifV- and wild-type nitrogenases from Klebsiella pneumoniae

1989 ◽  
Vol 258 (2) ◽  
pp. 487-491 ◽  
Author(s):  
J P Gemoets ◽  
M Bravo ◽  
C E McKenna ◽  
G J Leigh ◽  
B E Smith
Keyword(s):  
Klebsiella Pneumoniae ◽  
Azotobacter Vinelandii ◽  
Electron Flux ◽  
H2 Production ◽  
Relative Increase ◽  
Analogous Reaction ◽  
Wild Type ◽  
H2 Evolution ◽  
Product Ratio ◽  
In The Wild

The nitrogenase from wild-type Klebsiella pneumoniae reduces cyclopropene to cyclopropane and propene in the ratio 1:2 at pH 7.5. We show in this paper that the nitrogenase from a nifV mutant of K. pneumoniae also reduces cyclopropene to cyclopropane and propene, but the ratio of products is now 1:1.4. However, both nitrogenases exhibit the same Km for cyclopropene (2.1 x 10(4) +/- 0.2 x 10(4) Pa), considerably more than the Km for the analogous reaction with Azotobacter vinelandii nitrogenase under the same conditions (5.1 x 10(3) Pa). Analysis of the data shows that the different product ratio arises from the slower production of propene compared with cyclopropane by the mutant nitrogenase. During turnover, both nitrogenases use a large proportion of the electron flux for H2 production. CO inhibits the reduction of cyclopropene by both K. pneumoniae proteins, but the mutant nitrogenase exhibits 50% inhibition at approx. 10 Pa, whereas the corresponding value for the wild-type nitrogenase is approx. 110 Pa. However, H2 evolution by the mutant enzyme is much less affected than is cyclopropene reduction. CO inhibition of cyclopropene reduction by the nitrogenases coincides with a relative increase in H2 evolution, so that in the wild-type (but not the mutant) the electron flux is approximately maintained. The cyclopropane/propene production ratios are little affected by the presence of CO within the pressure ranges studied at least up to 50% inhibition.

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.

scholarly journals Saccharomyces cerevisiae null mutants in glucose phosphorylation: metabolism and invertase expression.

Genetics ◽  
1991 ◽  
Vol 128 (3) ◽  
pp. 521-527 ◽  
Author(s):  
R B Walsh ◽  
D Clifton ◽  
J Horak ◽  
D G Fraenkel
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Wild Type ◽  
Aerobic Growth ◽  
Triple Mutant ◽  
Hexokinase 2 ◽  
Glucose Flux ◽  
In The Wild ◽  
Glucose Phosphorylation ◽  
Different Strains

Abstract A congenic series of Saccharomyces cerevisiae strains has been constructed which carry, in all combinations, null mutations in the three genes for glucose phosphorylation: HXK1, HXK2 and GLK1, coding hexokinase 1 (also called PI or A), hexokinase 2 (PII or B), and glucokinase, respectively: i.e., eight strains, all of which grow on glucose except for the triple mutant. All or several of the strains were characterized in their steady state batch growth with 0.2% or 2% glucose, in aerobic as well as respiration-inhibited conditions, with respect to growth rate, yield, and ethanol formation. Glucose flux values were generally similar for different strains and conditions, provided they contained either hexokinase 1 or hexokinase 2. And their aerobic growth, as known for wild type, was largely fermentative with ca. 1.5 mol ethanol made per mol glucose used. The strain lacking both hexokinases and containing glucokinase was an exception in having reduced flux, a result fitting with its maximal rate of glucose phosphorylation in vitro. Aerobic growth of even the latter strain was largely fermentative (ca. 1 mol ethanol per mol glucose). Invertase expression was determined for a variety of media. All strains with HXK2 showed repression in growth on glucose and the others did not. Derepression in the wild-type strain occurred at ca. 1 mM glucose. The metabolic data do not support- or disprove-a model with HXK2 having only a secondary role in catabolite repression related to more rapid metabolism.

scholarly journals Hydrogen Photoproduction by Immobilized N2-Fixing Cyanobacteria: Understanding the Role of the Uptake Hydrogenase in the Long-Term Process

2014 ◽  
Vol 80 (18) ◽  
pp. 5807-5817 ◽  
Author(s):  
Sergey Kosourov ◽  
Hannu Leino ◽  
Gayathri Murukesan ◽  
Fiona Lynch ◽  
Kaarina Sivonen ◽  
...  
Keyword(s):  
Photosynthetic Activity ◽  
Nitrogenase Activity ◽  
Photosynthetic Apparatus ◽  
Hydrogenase Activity ◽  
Uptake Hydrogenase ◽  
Wild Type ◽  
Vegetative Cells ◽  
Content Type ◽  
N Deficiency ◽  
Pcc 7120

ABSTRACTWe have investigated two approaches to enhance and extend H2photoproduction yields in heterocystous, N2-fixing cyanobacteria entrapped in thin alginate films. In the first approach, periodic CO2supplementation was provided to alginate-entrapped, N-deprived cells. N deprivation led to the inhibition of photosynthetic activity in vegetative cells and the attenuation of H2production over time. Our results demonstrated that alginate-entrapped ΔhupLcells were considerably more sensitive to high light intensity, N deficiency, and imbalances in C/N ratios than wild-type cells. In the second approach,Anabaenastrain PCC 7120, its ΔhupLmutant, andCalothrixstrain 336/3 films were supplemented with N2by periodic treatments of air, or air plus CO2. These treatments restored the photosynthetic activity of the cells and led to a high level of H2production inCalothrix336/3 and ΔhupLcells (except for the treatment air plus CO2) but not in theAnabaenaPCC 7120 strain (for which H2yields did not change after air treatments). The highest H2yield was obtained by the air treatment of ΔhupLcells. Notably, the supplementation of CO2under an air atmosphere led to prominent symptoms of N deficiency in the ΔhupLstrain but not in the wild-type strain. We propose that uptake hydrogenase activity in heterocystous cyanobacteria not only supports nitrogenase activity by removing excess O2from heterocysts but also indirectly protects the photosynthetic apparatus of vegetative cells from photoinhibition, especially under stressful conditions that cause an imbalance in the C/N ratio in cells.

Identification and partial characterization of an Escherichia coli mutant with altered hydrogenase activity

1980 ◽  
Vol 58 (4) ◽  
pp. 361-367 ◽  
Author(s):  
Bernard R. Glick ◽  
Patrick Y. Wang ◽  
Henry Schneider ◽  
William G. Martin
Keyword(s):  
Escherichia Coli ◽  
Mutant Strain ◽  
Filter Paper ◽  
Specific Activity ◽  
Anaerobic Growth ◽  
Hydrogenase Activity ◽  
Wild Type ◽  
Coli Mutant ◽  
In The Wild ◽  
Membrane Bound

An Escherichia coli mutant strain with altered hydrogenase activity was isolated using a filter paper assay. This assay depends on the ability of hydrogenase-containing microorganisms to reduce methyl viologen impregnated in filter paper, producing purple-colored colonies in the presence of hydrogen. Membrane-bound and cytoplasmic hydrogenase activities of wild-type and mutant strains were compared by amperometric measurement of hydrogen production. The cytoplasmic activities of mutant and wild type were comparable. The membrane-bound activity was lower in the mutant than in the wild type. Upon addition of detergent to the membrane fraction the specific activity of the enzyme from the mutant strain increased so that it equalled that of the wild type. The mutant requires an exogenous electron acceptor for anaerobic growth providing evidence for the function of the hydrogenase in anaerobic growth.

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