Nitrogen Fixation and Nitrate Respiration by A zospirillum brasilense

1983 ◽  
Vol 38 (7-8) ◽  
pp. 571-577 ◽  
Author(s):  
Hermann Bothe ◽  
Gislene Barbosa ◽  
Johanna Dobereiner
Keyword(s):  
Nitrogen Fixation ◽  
Nitrate Reduction ◽  
Azospirillum Brasilense ◽  
Nitrate Respiration ◽  
Present Communication ◽  
Reaction Proceeding ◽  
Physiological Properties ◽  
Assimilatory Nitrate Reduction

The O2- sensitivitiy of N2-fixation by the carotenoid forming strain Azospirillum brasilense Cd and the colourless strain Sp 7 is compared in the present communication. As no difference in the reaction is observed with both strains, it is concluded that carotenoids do not protect nitrogenase from damage by O2. Azospirillum spp. have also been shown to perform NO3-- dependent N2-fixation. The physiological properties of this reaction are described in more detail in the present communication. Evidence is presented that NO3-- dependent N2-fixation is a transitory reaction, proceeding only as long as the enzymes of assimilatory nitrate reduction are synthesized by the cells.

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 Genome Analysis of a Marine Bacterium Halomonas sp. and Its Role in Nitrate Reduction under the Influence of Photoelectrons

2020 ◽  
Vol 8 (10) ◽  
pp. 1529
Author(s):  
Ying Liu ◽  
Hongrui Ding ◽  
Yuan Sun ◽  
Yan Li ◽  
Anhuai Lu
Keyword(s):  
Genome Analysis ◽  
Nitrate Reduction ◽  
Nitrogen Loss ◽  
Light Response ◽  
Open Circuit ◽  
The Yellow Sea ◽  
Photic Zone ◽  
Whole Genome Analysis ◽  
Genes Encoding ◽  
Assimilatory Nitrate Reduction

The solar light response and photoelectrons produced by widespread semiconducting mineral play important roles in biogeochemical cycles on Earth’s surface. To explore the potential influence of photoelectrons generated by semiconducting mineral particles on nitrate-reducing microorganisms in the photic zone, a marine heterotrophic denitrifier Halomonas sp. strain 3727 was isolated from seawater in the photic zone of the Yellow Sea, China. This strain was classified as a Halomonadaceae. Whole-genome analysis indicated that this strain possessed genes encoding the nitrogen metabolism, i.e., narG, nasA, nirBD, norZ, nosB, and nxr, which sustained dissimilatory nitrate reduction, assimilatory nitrate reduction, and nitrite oxidation. This strain also possessed genes related to carbon, sulfur, and other metabolisms, hinting at its substantial metabolic flexibility. A series of microcosm experiments in a simulative photoelectron system was conducted, and the results suggested that this bacterial strain could use simulated photoelectrons with different energy for nitrate reduction. Nitrite, as an intermediate product, was accumulated during the nitrate reduction with limited ammonia residue. The nitrite and ammonia productions differed with or without different energy electron supplies. Nitrite was the main product accounting for 30.03% to 68.40% of the total nitrogen in photoelectron supplement systems, and ammonia accounted for 3.77% to 8.52%. However, in open-circuit systems, nitrite and ammonia proportions were 26.77% and 11.17%, respectively, and nitrogen loss in the liquid was not observed. This study reveals that photoelectrons can serve as electron donors for nitrogen transformation mediated by Halomonas sp. strain 3727, which reveals an underlying impact on the nitrogen biogeochemical cycle in the marine photic zone.

scholarly journals Activity of Spore-Specific Respiratory Nitrate Reductase 1 ofStreptomyces coelicolorA3(2) Requires a Functional Cytochromebcc-aa3Oxidase Supercomplex

2019 ◽  
Vol 201 (11) ◽  
Author(s):  
Dörte Falke ◽  
Bianca Biefel ◽  
Alexander Haase ◽  
Stefan Franke ◽  
Marco Fischer ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Nitrate Reductase ◽  
Nitrate Reduction ◽  
Streptomyces Coelicolor ◽  
Nitrate Respiration ◽  
Nitrate Transport ◽  
Developmental Cycle ◽  
Content Type ◽  
Resting Spores ◽  
Respiratory Nitrate Reductase

ABSTRACTSpores have strongly reduced metabolic activity and are produced during the complex developmental cycle of the actinobacteriumStreptomyces coelicolor. Resting spores can remain viable for decades, yet little is known about how they conserve energy. It is known, however, that they can reduce either oxygen or nitrate using endogenous electron sources.S. coelicoloruses either a cytochromebdoxidase or a cytochromebcc-aa3oxidase supercomplex to reduce oxygen, while nitrate is reduced by Nar-type nitrate reductases, which typically oxidize quinol directly. Here, we show that in resting spores the Nar1 nitrate reductase requires a functionalbcc-aa3supercomplex to reduce nitrate. Mutants lacking the completeqcr-ctagenetic locus encoding thebcc-aa3supercomplex showed no Nar1-dependent nitrate reduction. Recovery of Nar1 activity was achieved by genetic complementation but only when the completeqcr-ctalocus was reintroduced to the mutant strain. We could exclude that the dependence on the supercomplex for nitrate reduction was via regulation of nitrate transport. Moreover, the catalytic subunit, NarG1, of Nar1 was synthesized in theqcr-ctamutant, ruling out transcriptional control. Constitutive synthesis of Nar1 in mycelium revealed that the enzyme was poorly active in this compartment, suggesting that the Nar1 enzyme cannot act as a typical quinol oxidase. Notably, nitrate reduction by the Nar2 enzyme, which is active in growing mycelium, was not wholly dependent on thebcc-aa3supercomplex for activity. Together, our data suggest that Nar1 functions together with the proton-translocatingbcc-aa3supercomplex to increase the efficiency of energy conservation in resting spores.IMPORTANCEStreptomyces coelicolorforms spores that respire with either oxygen or nitrate, using only endogenous electron donors. This helps maintain a membrane potential and, thus, viability. Respiratory nitrate reductase (Nar) usually receives electrons directly from reduced quinone species; however, we show that nitrate respiration in spores requires a respiratory supercomplex comprising cytochromebccoxidoreductase andaa3oxidase. Our findings suggest that the Nar1 enzyme in theS. coelicolorspore functions together with the proton-translocatingbcc-aa3supercomplex to help maintain the membrane potential more efficiently. Dissecting the mechanisms underlying this survival strategy is important for our general understanding of bacterial persistence during infection processes and of how bacteria might deal with nutrient limitation in the natural environment.

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