Molybdenum incorporation in denitrifying Azospirillum brasilense Sp7

1992 ◽  
Vol 38 (10) ◽  
pp. 1042-1047 ◽  
Author(s):  
Christian Chauret ◽  
Wilfredo L. Barraquio ◽  
Roger Knowles
Keyword(s):  
Nitrate Reductase ◽  
Key Words ◽  
Nitrate Reduction ◽  
Gel Electrophoresis ◽  
Azospirillum Brasilense ◽  
Paracoccus Denitrificans ◽  
Free Medium ◽  
Azospirillum Brasilense Sp7

Nondenaturating disc gel electrophoresis revealed that 99Mo was incorporated into the nitrate reductase of Azospirillum brasilense grown in the absence but not in the presence of tungstate. Under denitrifying conditions, A. brasilense grown in tungsten-free medium steadily accumulated 99Mo for 12 h. In contrast, Paracoccus denitrificans grown under the same conditions ceased uptake after 1 h. However, both bacteria were incapable of accumulating significant amounts of 99Mo in media containing 10 mM tungstate, even though nitrate was reduced by A. brasilense. Aerobically grown A. brasilense cells transported 99Mo more efficiently than anaerobically grown cells. Key words: Azospirillum brasilense, tungsten, molybdenum incorporation, nitrate reduction.

scholarly journals Effect of tungsten on nitrate and nitrite reductases in Azospirillum brasilense Sp7

1991 ◽  
Vol 37 (10) ◽  
pp. 744-750 ◽  
Author(s):  
Christian Chauret ◽  
Roger Knowles
Keyword(s):  
Nitrate Reductase ◽  
Nitrite Reductase ◽  
Azospirillum Brasilense ◽  
Nitrate Reductase Activity ◽  
Paracoccus Denitrificans ◽  
Reductase Activity ◽  
Whole Cells ◽  
Azospirillum Brasilense Sp7 ◽  
Nitrite Reductase Activity ◽  
Nitrate And Nitrite

Tungstate, at concentrations that completely suppressed nitrate reductase activity in Paracoccus denitrificans, caused only partial inhibition of nitrate reductase in Azospirillum brasilense Sp7. Nitrate reductase activity in cell-free extracts was much more sensitive than whole cells to tungstate, suggesting that there may be a barrier to its transport. Nitrite reductase activity was partially inhibited by tungstate in both whole cells and cell-free extracts. Azospirillum brasilense apparently scavenged enough contaminating molybdenum from molybdenum-limited medium to allow maximum nitrate reductase activity, which was not stimulated by added molybdate. Cells grown in molybdenum-depleted medium could not reduce nitrate. Nitrate concentrations less than 0.25 mM inhibited activity, but not synthesis, of nitrite reductase and caused significant accumulation of nitrite during reduction of nitrate. Key words: Azospirillum brasilense, Paracoccus denitrificans, nitrate reductase, nitrite reductase, tungsten, molybdenum, denitrification.

scholarly journals The location of dissimilatory nitrite reductase and the control of dissimilatory nitrate reductase by oxygen in Paracoccus denitrificans

1980 ◽  
Vol 192 (1) ◽  
pp. 231-240 ◽  
Author(s):  
P R Alefounder ◽  
S J Ferguson
Keyword(s):  
Plasma Membrane ◽  
Nitrate Reductase ◽  
Nitrate Reduction ◽  
Paracoccus Denitrificans ◽  
Osmotic Shock ◽  
Inhibitory Effect ◽  
Nitrate Respiration ◽  
Permeability Barrier ◽  
Intact Cells ◽  
Close Relationship

1. A method is described for preparing spheroplasts from Paracoccus denitrificans that are substantially depleted of dissimilatory nitrate reductase (cytochrome cd) activity. Treatment of cells with lysozyme + EDTA together with a mild osmotic shock, followed by centrifugation, yielded a pellet of spheroplasts and a supernatant that contained d-type cytochrome. The spheroplasts were judged to have retained an intact plasma membrane on the basis that less than 1% of the activity of a cytoplasmic marker protein, malate dehydrogenase, was released from the spheroplasts. In addition to a low activity towards added nitrite, the suspension of spheroplasts accumulated the nitrite that was produced by respiratory chain-linked reduction of nitrate. It is concluded that nitrate reduction occurs at the periplasmic side of the plasma membrane irrespective of whether nitrite is generated by nitrate reduction or is added exogenously. 2. Further evidence for the integrity of the spheroplasts was that nitrate reduction was inhibited by O2, and that chlorate was reduced at a markedly lower rate than nitrate. These data are taken as evidence for an intact plasma membrane because it was shown that cells acquire the capability to reduce nitrate under aerobic conditions after addition of low amounts of Triton X-100 which, with the same titre, also overcame the permeability barrier to chlorate reduction by intact cells. The close relationship between the appearance of chlorate reduction and the loss of the inhibitory effect of O2 on nitrate reduction also suggests that the later feature of nitrate respiration is due to a control on the accessibility of nitrate to its reductase rather than on the flow of electrons to nitrate reductase.

scholarly journals Interference of chlorate and chlorite with nitrate reduction in resting cells of Paracoccus denitrificans

Microbiology ◽  
2006 ◽  
Vol 152 (12) ◽  
pp. 3529-3534 ◽  
Author(s):  
Igor Kučera
Keyword(s):  
Cell Membrane ◽  
Nitrate Reductase ◽  
Nitrate Reduction ◽  
Paracoccus Denitrificans ◽  
Metabolic Activation ◽  
Partial Purification ◽  
Resting Cells ◽  
Aerobic Growth ◽  
Membrane Bound ◽  
Periplasmic Enzyme

When grown anaerobically on a succinate+nitrate (SN) medium, Paracoccus denitrificans forms the membrane-bound, cytoplasmically oriented, chlorate-reducing nitrate reductase Nar, while the periplasmic enzyme Nap is expressed during aerobic growth on butyrate+oxygen (BO) medium. Preincubation of SN cells with chlorate produced a concentration-dependent decrease in nitrate utilization, which could be ascribed to Nar inactivation. Toluenization rendered Nar less sensitive to chlorate, but more sensitive to chlorite, suggesting that the latter compound may be the true inactivator. The Nap enzyme of BO cells was inactivated by both chlorate and chlorite at concentrations that were at least two orders of magnitude lower than those shown to affect Nar. Partial purification of Nap resulted in insensitivity to chlorate and diminished sensitivity to chlorite. Azide was specific for SN cells in protecting nitrate reductase against chlorate attack, the protective effect of nitrate being more pronounced in BO cells. The results are discussed in terms of different metabolic activation of chlorine oxoanions in both types of cells, and limited permeation of chlorite across the cell membrane.

Some metabolic responses of bush bean plants to a subherbicidal concentration of certain s-triazine compounds

1970 ◽  
Vol 48 (12) ◽  
pp. 2213-2217 ◽  
Author(s):  
B. Singh ◽  
D. K. Salunkhe
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reduction ◽  
Adenosine Triphosphatase ◽  
Acid Synthesis ◽  
Controlled Environment ◽  
Transaminase Activity ◽  
Starch Phosphorylase ◽  
Phaseolus Vulgaris L ◽  
Bean Plants ◽  
Bush Bean

A solution containing 0.5 p.p.m. of atrazine, simazine, igran, or GS-14254 with 0.2% triton-B 1956 was applied to the foliage of 11-day-old seedlings of bush beans, Phaseolus vulgaris L. cultivar Tender-green, growing on vermiculite in a controlled environment. The activities of nitrate reductase, glutamic-pyruvic transaminase, α-amylase, starch phosphorylase, and adenosine triphosphatase were determined 5,10, and 20 days after treatment. In general, the activity of each of the five enzymes was stimulated by the treatment. The results suggest that protein increase following the application of.s-triazines to bean plants may stem in part from an enhanced rate of amino acid formation resulting from the induced increment in nitrate reductase and transaminase activity. The application of these chemicals also creates a metabolic condition favorable for greater use of carbohydrates needed for nitrate reduction and protein synthesis, and as a source of organic acid synthesis.

Role of a Fasciclin domain protein in photooxidative stress and flocculation in Azospirillum brasilense Sp7

2021 ◽  
pp. 103875
Author(s):  
Ashutosh Prakash Dubey ◽  
Parul Pandey ◽  
Shivangi Mishra ◽  
Parikshit Gupta ◽  
Anil Kumar Tripathi
Keyword(s):  
Azospirillum Brasilense ◽  
Photooxidative Stress ◽  
Azospirillum Brasilense Sp7 ◽  
Domain Protein

scholarly journals Two different modes of attachment of Azospirillum brasilense Sp7 to wheat roots

1991 ◽  
Vol 137 (9) ◽  
pp. 2241-2246 ◽  
Author(s):  
K. W. Michiels ◽  
C. L. Croes ◽  
J. Vanderleyden
Keyword(s):  
Azospirillum Brasilense ◽  
Wheat Roots ◽  
Azospirillum Brasilense Sp7

Voltammetric characterization of the aerobic energy-dissipating nitrate reductase of Paracoccus pantotrophus: exploring the activity of a redox-balancing enzyme as a function of electrochemical potential

2007 ◽  
Vol 409 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Andrew J. Gates ◽  
David J. Richardson ◽  
Julea N. Butt
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reduction ◽  
Reductase Activity ◽  
Electrochemical Potential ◽  
Intact Cells ◽  
Protein Film ◽  
Protein Film Voltammetry ◽  
Voltammetric Studies ◽  
Paracoccus Pantotrophus

Paracoccus pantotrophus expresses two nitrate reductases associated with respiratory electron transport, termed NapABC and NarGHI. Both enzymes derive electrons from ubiquinol to reduce nitrate to nitrite. However, while NarGHI harnesses the energy of the quinol/nitrate couple to generate a transmembrane proton gradient, NapABC dissipates the energy associated with these reducing equivalents. In the present paper we explore the nitrate reductase activity of purified NapAB as a function of electrochemical potential, substrate concentration and pH using protein film voltammetry. Nitrate reduction by NapAB is shown to occur at potentials below approx. 0.1 V at pH 7. These are lower potentials than required for NarGH nitrate reduction. The potentials required for Nap nitrate reduction are also likely to require ubiquinol/ubiquinone ratios higher than are needed to activate the H+-pumping oxidases expressed during aerobic growth where Nap levels are maximal. Thus the operational potentials of P. pantotrophus NapAB are consistent with a productive role in redox balancing. A Michaelis constant (KM) of approx. 45 μM was determined for NapAB nitrate reduction at pH 7. This is in line with studies on intact cells where nitrate reduction by Nap was described by a Monod constant (KS) of less than 15 μM. The voltammetric studies also disclosed maximal NapAB activity in a narrow window of potential. This behaviour is resistant to change of pH, nitrate concentration and inhibitor concentration and its possible mechanistic origins are discussed.

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