scholarly journals Effect of ruminal administration ofEscherichia coliwild type or a genetically modified strain with enhanced high nitrite reductase activity on methane emission and nitrate toxicity in nitrate-infused sheep

2005 ◽  
Vol 94 (5) ◽  
pp. 691-697 ◽  
Author(s):  
C. Sar ◽  
B. Mwenya ◽  
B. Pen ◽  
K. Takaura ◽  
R. Morikawa ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Body Weight ◽  
Single Dose ◽  
Methane Emission ◽  
Nitrite Reductase ◽  
Reductase Activity ◽  
Wild Type ◽  
E Coli ◽  
Reduction Activity ◽  
Nitrite Reductase Activity

The effects of two kinds ofEscherichia coli(E. coli) strain, wild-typeE. coliW3110 andE. colinir-Ptac, which has enhanced NO2reduction activity, on oral CH4emission and NO3toxicity in NO3-treated sheep were assessed in a respiratory hood system in a 4×6 Youden square design. NO3(1·3g NaNO3/kg0·75body weight) and/orE. colistrains were delivered into the rumen through a fistula as a single dose 30min after the morning meal.Escherichia colicells were inoculated for sheep to provide an initialE. colicell density of optical density at 660nm of 2, which corresponded to 2×1010cells/ml. The six treatments consisted of saline,E. coliW3110,E. colinir-Ptac, NO3, NO3plusE. coliW3110, and NO3plusE. colinir-Ptac. CH4emission from sheep was reduced by the inoculation ofE. coliW3110 orE. colinir-Ptac by 6% and 12%, respectively. NO3markedly inhibited CH4emission from sheep. Compared with sheep given NO3alone, the inoculation ofE. coliW3110 to NO3-infused sheep lessened ruminal and plasma toxic NO2accumulation and blood methaemoglobin production, while keeping ruminal methanogenesis low. Ruminal and plasma toxic NO2accumulation and blood methaemoglobin production in sheep were unaffected by the inoculation ofE. colinir-Ptac. These results suggest that ruminal methanogenesis may be reduced by the inoculation ofE. coliW3110 orE. colinir-Ptac. The inoculation ofE. coliW3110 may abate NO3toxicity when NO3is used to inhibit CH4emission from ruminants.

ucFabV Requires Functional Reductase Activity to Confer Reduced Triclosan Susceptibility in Escherichia coli

2015 ◽  
Vol 25 (6) ◽  
pp. 394-402 ◽  
Author(s):  
Taylor L. Fischer ◽  
Robert J. White ◽  
Katherine F.K. Mares ◽  
Devin E. Molnau ◽  
Justin J. Donato
Keyword(s):  
Escherichia Coli ◽  
Reductase Activity ◽  
Acid Synthesis ◽  
Temperature Sensitive ◽  
Wild Type ◽  
E Coli ◽  
Enoyl Acp Reductase ◽  
Selection For

<b><i>Background/Aims:</i></b> We previously identified the Triclo1 fosmid in a functional metagenomic selection for clones that increased triclosan tolerance in <i>Escherichia coli</i>. The active enzyme encoded by Triclo1 is ucFabV. Although ucFabV is homologous to FabV from other organisms, ucFabV contains substitutions at key positions that would predict differences in substrate binding. Therefore, a detailed characterization of ucFabV was conducted to link its biochemical activity to its ability to confer reduced triclosan sensitivity. <b><i>Methods:</i></b> ucFabV and a catalytic mutant were purified and used to reduce crotonoyl-CoA in vitro. The mutant and wild-type enzymes were introduced into <i>E. coli</i>, and their ability to confer triclosan tolerance as well as suppress a temperature-sensitive mutant of FabI were measured. <b><i>Results:</i></b> Purified ucFabV, but not the mutant, reduced crotonoyl-CoA in vitro. The wild-type enzyme confers increased triclosan tolerance when introduced into <i>E. coli</i>, whereas the mutant remained susceptible to triclosan<i>. </i>Additionally, wild-type ucFabV, but not the mutant, functionally replaced FabI within living cells. <b><i>Conclusion:</i></b> ucFabV confers increased tolerance through its function as an enoyl-ACP reductase. Furthermore, ucFabV is capable of restoring viability in the presence of compromised FabI, suggesting ucFabV is likely facilitating an alternate step within fatty acid synthesis, bypassing FabI inhibition.

scholarly journals Involvement of the PrrB/PrrA Two-Component System in Nitrite Respiration in Rhodobacter sphaeroides 2.4.3: Evidence for Transcriptional Regulation

2002 ◽  
Vol 184 (13) ◽  
pp. 3521-3529 ◽  
Author(s):  
William P. Laratta ◽  
Peter S. Choi ◽  
Ivan E. Tosques ◽  
James P. Shapleigh
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Nitrite Reductase ◽  
Response Regulator ◽  
Reductase Activity ◽  
Wild Type ◽  
Gene Encoding ◽  
Wild Type Phenotype ◽  
Two Component ◽  
Nitrite Reductase Activity ◽  
Nitrite Respiration

ABSTRACT Rhodobacter sphaeroides strain 2.4.3 is capable of diverse metabolic lifestyles, including denitrification. The regulation of many Rhodobacter genes involved in redox processes is controlled, in part, by the PrrBA two-component sensor-regulator system, where PrrB serves as the sensor kinase and PrrA is the response regulator. Four strains of 2.4.3 carrying mutations within the prrB gene were isolated in a screen for mutants unable to grow anaerobically on medium containing nitrite. Studies revealed that the expression of nirK, the structural gene encoding nitrite reductase, in these strains was significantly decreased compared to its expression in 2.4.3. Disruption of prrA also eliminated the ability to grow both photosynthetically and anaerobically in the dark on nitrite-amended medium. Complementation with prrA restored the wild-type phenotype. The PrrA strain exhibited a severe decrease in both nitrite reductase activity and expression of a nirK-lacZ fusion. Nitrite reductase activity in the PrrA strain could be restored to wild-type levels by using nirK expressed from a heterologous promoter, suggesting that the loss of nitrite reductase activity in the PrrA and PrrB mutants was not due to problems with enzyme assembly or the supply of reductant. Inactivation of prrA had no effect on the expression of the gene encoding NnrR, a transcriptional activator required for the expression of nirK. Inactivation of ccoN, part of the cbb 3-type cytochrome oxidase shown to regulate the kinase activity of PrrB, also caused a significant decrease in both nirK expression and Nir activity. This was unexpected, since PrrA-P accumulates in the ccoN strain. Together, these results demonstrate that PrrBA plays an essential role in the regulation of nirK.

A mutation leading to the total lack of nitrite reductase activity in Escherichia coli K 12

1978 ◽  
Vol 160 (2) ◽  
pp. 225-229 ◽  
Author(s):  
M. Chippaux ◽  
D. Giudici ◽  
A. Abou-Jaoudé ◽  
F. Casse ◽  
M. C. Pascal
Keyword(s):  
Escherichia Coli ◽  
Nitrite Reductase ◽  
Reductase Activity ◽  
Nitrite Reductase Activity ◽  
Total Lack ◽  
K 12

scholarly journals Sites and specificity of the reaction of bipyridylium compounds with anaerobic respiratory enzymes of Escherichia coli. Effects of permeability barriers imposed by the cytoplasmic membrane

1977 ◽  
Vol 164 (1) ◽  
pp. 199-211 ◽  
Author(s):  
Robert W. Jones ◽  
Peter B. Garland
Keyword(s):  
Escherichia Coli ◽  
Nitrate Reductase ◽  
Cytoplasmic Membrane ◽  
Reductase Activity ◽  
Membrane Vesicles ◽  
Respiratory Enzymes ◽  
Radical Species ◽  
Benzyl Viologen ◽  
E Coli ◽  
Nitrite Reductase Activity

The ability of the oxidized and singly reduced species of several bipyridylium cations to cross the cytoplasmic membrane of Escherichia coli was studied to locate the sites of reaction of the dyes with anaerobic respiratory enzymes. Benzyl Viologen radical crossed the membrane rapidly, whereas the oxidized species did not. The oxidized or radical species of Methyl Viologen, Morfamquat or Diquat did not rapidly cross the membrane. It was also shown that the dithionite anion does not cross the cytoplasmic membrane of E. coli. Diquat radical donates electrons to the nitrate reductase pathway at the periplasmic aspect of the membrane, whereas Benzyl Viologen radical reacted directly with nitrate reductase itself (EC 1.7.99.4) at the cytoplasmic aspect of the membrane. Thus the pathway of electron transfer in the nitrate reductase pathway is transmembranous. Formate hydrogenlyase (EC 1.2.1.2) and an uncharacterized nitrite reductase activity react with bipyridylium dyes at the periplasmic aspect of the membrane. Fumarate reductase (succinate dehydrogenase; EC 1.3.99.1) reacts with bipyridylium radicals, and formate dehydrogenase (cytochrome) (EC 1.2.2.1) with ferricyanide, at the cytoplasmic aspect of the membrane. The differing charge and membrane permeation of oxidized and radical species of bipyridylium dyes greatly complicate their use as potentiometric mediators in suspensions of cells or membrane vesicles.

scholarly journals In Escherichia coli Ammonia Inhibits Cytochrome bo3 But Activates Cytochrome bd-I

Antioxidants ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 13
Author(s):  
Elena Forte ◽  
Sergey A. Siletsky ◽  
Vitaliy B. Borisov
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Dissociation Constants ◽  
Reductase Activity ◽  
Ammonia Concentration ◽  
High Concentration ◽  
E Coli ◽  
Cytochrome Bd ◽  
Cytochrome Bo3 ◽  
Oxygen Reductase

Interaction of two redox enzymes of Escherichia coli, cytochrome bo3 and cytochrome bd-I, with ammonium sulfate/ammonia at pH 7.0 and 8.3 was studied using high-resolution respirometry and absorption spectroscopy. At pH 7.0, the oxygen reductase activity of none of the enzymes is affected by the ligand. At pH 8.3, cytochrome bo3 is inhibited by the ligand, with 40% maximum inhibition at 100 mM (NH4)2SO4. In contrast, the activity of cytochrome bd-I at pH 8.3 increases with increasing the ligand concentration, the largest increase (140%) is observed at 100 mM (NH4)2SO4. In both cases, the effector molecule is apparently not NH4+ but NH3. The ligand induces changes in absorption spectra of both oxidized cytochromes at pH 8.3. The magnitude of these changes increases as ammonia concentration is increased, yielding apparent dissociation constants Kdapp of 24.3 ± 2.7 mM (NH4)2SO4 (4.9 ± 0.5 mM NH3) for the Soret region in cytochrome bo3, and 35.9 ± 7.1 and 24.6 ± 12.4 mM (NH4)2SO4 (7.2 ± 1.4 and 4.9 ± 2.5 mM NH3) for the Soret and visible regions, respectively, in cytochrome bd-I. Consistently, addition of (NH4)2SO4 to cells of the E. coli mutant containing cytochrome bd-I as the only terminal oxidase at pH 8.3 accelerates the O2 consumption rate, the highest one (140%) being at 27 mM (NH4)2SO4. We discuss possible molecular mechanisms and physiological significance of modulation of the enzymatic activities by ammonia present at high concentration in the intestines, a niche occupied by E. coli.

Inhibition of Escherichia coli Trimethylamine-N-oxide Reductase by Food Preservatives1

1982 ◽  
Vol 45 (3) ◽  
pp. 241-243 ◽  
Author(s):  
M. KRUK ◽  
J. S. LEE
Keyword(s):  
Escherichia Coli ◽  
Benzoic Acid ◽  
Sorbic Acid ◽  
Reductase Activity ◽  
Resting Cells ◽  
E Coli

Trimethylamine-N-oxide (TMA-O) reductase activity of resting cells of Escherichia coli was inhibited by tetrasodium ethylenediaminetetraacetate (Na4EDTA), benzoic acid (BA and methylparaben (MP). The 50% inhibitory concentrations of Na4EDTA, BA and MP were 20.2, 1.2 and 32.4 mM, respectively. BA at pH 6.5 or below most effectively inhibited the TMA-O reductase. Sorbic acid (SA), up to 0.70 mM, had no effect on TMA-O reductase activity, but SA inhibited the growth and subsequent TMA production in E. coli at or above 0.3S mM.

scholarly journals 0099. Nitrite reductase activity during sepsis

2014 ◽  
Vol 2 (S1) ◽  
Author(s):  
V Simon ◽  
A Dyson ◽  
M Minnion ◽  
M Feelisch ◽  
M Singer
Keyword(s):  
Nitrite Reductase ◽  
Reductase Activity ◽  
Nitrite Reductase Activity
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