The expression of redox proteins of denitrification inThiosphaera pantotropha grown with oxygen, nitrate, and nitrous oxide as electron acceptors

1995 ◽  
Vol 164 (1) ◽  
pp. 43-49 ◽  
Author(s):  
James W. B. Moir ◽  
David J. Richardson ◽  
Stuart J. Ferguson
Keyword(s):  
Nitrous Oxide ◽  
Electron Acceptors ◽  
Redox Proteins

Denitrification by Cytophaga johnsonae strains and by a gliding bacterium able to reduce nitrous oxide in the presence of acetylene and sulfide

1986 ◽  
Vol 32 (5) ◽  
pp. 421-424 ◽  
Author(s):  
Anne M. Adkins ◽  
Roger Knowles
Keyword(s):  
Nitrous Oxide ◽  
Nitrogen Oxide ◽  
Electron Acceptors ◽  
Gliding Bacteria ◽  
Gliding Bacterium

A gliding bacterium (Is-11), isolated for its ability to reduce nitrous oxide (N2O) in the presence of acetylene (C2H2) and sulfide, was able to use nitrate (NO3−), nitrite (NO2−), and N2O as terminal electron acceptors for growth. Similarly, of five strains of Cytophaga johnsonae examined, two were capable of complete denitrification. Two strains were unable to reduce nitrate and N2O, respectively, and the remaining strain lacked both nitrate and N2O reductases. However, in this strain the N2O reductase was induced by the presence of nitrite, but not nitrate. Acetylene inhibited N2O reduction but did not affect the reduction of nitrite or nitrate in all of the gliding bacteria tested. Sulfide temporarily inhibited all of the nitrogen oxide reductases. It did not relieve the C2H2 inhibition of N2O reduction in the C. johnsonae strains when tested under the same conditions under which C2H2 inhibition is relieved in Is-11.

scholarly journals Denitrification kinetics indicates nitrous oxide uptake is unaffected by electron competition in Accumulibacter

2020 ◽  
Author(s):  
Roy Samarpita ◽  
Pradhan Nirakar ◽  
NG How Yong ◽  
Wuertz Stefan
Keyword(s):  
Nitrous Oxide ◽  
Electron Acceptor ◽  
Phosphorus Removal ◽  
Metabolic Model ◽  
Electron Acceptors ◽  
Treatment Technology ◽  
Denitrifying Phosphorus Removal ◽  
Terminal Electron Acceptor ◽  
Efficient Treatment ◽  
Denitrification Kinetics

ABSTRACTDenitrifying phosphorus removal is a cost and energy efficient treatment technology that relies on polyphosphate accumulating organisms (DPAOs) utilizing nitrate or nitrite as terminal electron acceptor. Denitrification is a multistep process and many organisms do not possess the complete pathway, leading to the accumulation of intermediates such as nitrous oxide (N2O), a potent greenhouse gas and ozone depleting substance. Candidatus Accumulibacter organisms are prevalent in denitrifying phosphorus removal processes and, according to genomic analyses, appear to vary in their denitrification abilities based on their lineage. Yet, denitrification kinetics and nitrous oxide accumulation by Accumulibacter after long-term exposure to either nitrate or nitrite as electron acceptor have never been compared. We investigated the preferential use of the nitrogen oxides involved in denitrification and nitrous oxide accumulation in two enrichments of Accumulibacter and a competitor – the glycogen accumulating organism Candidatus Competibacter. A metabolic model was modified to predict phosphorus removal and denitrification rates when nitrate, nitrite or N2O were added as electron acceptors in different combinations. Unlike previous studies, no N2O accumulation was observed for Accumulibacter in the presence of multiple electron acceptors. Electron competition did not affect denitrification kinetics or N2O accumulation in Accumulibacter or Competibacter. Despite the presence of sufficient internal storage polymers (polyhydroxyalkanoates, or PHA) as energy source for each denitrification step, the extent of denitrification observed was dependent on the dominant organism in the enrichment. Accumulibacter showed complete denitrification and N2O utilization, whereas for Competibacter denitrification was limited to reduction of nitrate to nitrite. These findings indicate that DPAOs can contribute to lowering N2O emissions in the presence of multiple electron acceptors under partial nitritation conditions.

Denitrifïcation in Flexibacter canadensis

1990 ◽  
Vol 36 (6) ◽  
pp. 430-434 ◽  
Author(s):  
Alison M. Jones ◽  
Roger Knowles
Keyword(s):  
Nitrous Oxide ◽  
Sodium Sulfide ◽  
Electron Acceptors ◽  
Inhibition Assay ◽  
Oxide Reduction ◽  
Acetylene Inhibition ◽  
Gram Negative ◽  
Nitrous Oxide Reduction ◽  
Pure Cultures ◽  
Gliding Bacterium

Denitrifïcation was studied in pure cultures of Flexibacter canadensis (ATCC 29591), a Gram-negative gliding bacterium found in soil. Flexibacter canadensis was capable of using nitrate, nitrite, and nitrous oxide as terminal electron acceptors for growth. Sodium sulfide (200 μM) inhibited all of the nitrogen oxide reductases, but only temporarily. Acetylene (4 kPa) inhibited nitrous oxide reduction but did not affect the reduction of either nitrate or nitrite. However, sulfide (100 and 200 μM) alleviated the acetylene block and permitted reduction of nitrous oxide in the presence of 4 kPa acetylene. These data may have important implications regarding the use of the acetylene inhibition assay for measuring denitrifïcation rates in highly anaerobic, sulfidic environments. Key words: Flexibacter canadensis, denitrification, N2O reductase, sulfide, acetylene.

Electronic structure studies of conducting polymers by electron energy-loss spectroscopy

1996 ◽  
Vol 54 ◽  
pp. 160-161
Author(s):  
J. Fink
Keyword(s):  
Electronic Structure ◽  
Conducting Polymers ◽  
Conjugated Polymers ◽  
Electron Acceptors ◽  
Electron Donors ◽  
Light Emitting ◽  
One Dimensional ◽  
New Class ◽  
Electrical Conductivities ◽  
Electron Energy Loss

Conducting polymers comprises a new class of materials achieving electrical conductivities which rival those of the best metals. The parent compounds (conjugated polymers) are quasi-one-dimensional semiconductors. These polymers can be doped by electron acceptors or electron donors. The prototype of these materials is polyacetylene (PA). There are various other conjugated polymers such as polyparaphenylene, polyphenylenevinylene, polypoyrrole or polythiophene. The doped systems, i.e. the conducting polymers, have intersting potential technological applications such as replacement of conventional metals in electronic shielding and antistatic equipment, rechargable batteries, and flexible light emitting diodes.Although these systems have been investigated almost 20 years, the electronic structure of the doped metallic systems is not clear and even the reason for the gap in undoped semiconducting systems is under discussion.

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