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Related Concept Videos

Inorganic Nitrogen Assimilation01:22

Inorganic Nitrogen Assimilation

Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme nitrate reductase...
Overview of Nitrogen Metabolism01:20

Overview of Nitrogen Metabolism

Nitrogen is a very important element for life because it is a major constituent of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds and stored in the form of  ammonia, ammonium ions, nitrate, nitrite, or  nitrogen gas by many metabolic processes. Many of these metabolic processes are carried out only by prokaryotes.
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
Metabolism of Chemolithotrophs01:15

Metabolism of Chemolithotrophs

Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation. However, because inorganic electron donors...
The Nitrogen Cycle01:49

The Nitrogen Cycle

Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of nitrogen on Earth is nitrogen gas, which cannot be used by most animals and plants. Thus, nitrogen gas must first be converted into a usable form by nitrogen-fixing bacteria before it can be cycled through other living organisms. The use of nitrogen-containing fertilizers and animal waste products in human agriculture has greatly influenced the...
Microbes and Methanogenesis01:26

Microbes and Methanogenesis

Methanogenesis is a critical microbial process in anaerobic ecosystems responsible for the biological production of methane, a potent greenhouse gas and valuable biofuel. This metabolic pathway is primarily facilitated by methanogenic archaea, which thrive in anoxic environments such as wetlands, sediments, and animal gastrointestinal tracts. The absence of oxygen in these habitats prevents aerobic respiration, thereby favoring alternative biochemical pathways for organic matter degradation.In...
Microbial Interactions: Mutualism01:25

Microbial Interactions: Mutualism

Mutualism is a symbiotic interaction in which all participating organisms benefit. These relationships can be obligate or facultative and are fundamental to ecosystem functions across diverse biological systems.Plant–Fungi MutualismOne well-known example is the association between plant roots and mycorrhizal fungi, such as Rhizophagus species. The fungal hyphae penetrate the root hairs and the epidermis, forming an extensive hyphal network that establishes a symbiotic association. Through this...

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Related Experiment Video

Updated: May 27, 2026

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti
20:01

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti

Published on: October 1, 2013

Denitrification in Sinorhizobium meliloti.

María J Torres1, María I Rubia, Eulogio J Bedmar

  • 1Estación Experimental del Zaidín, CSIC, PO Box 419, 18080-Granada, Spain.

Biochemical Society Transactions
|November 23, 2011
PubMed
Summary

Sinorhizobium meliloti can grow using nitrate or nitrite as respiratory substrates under micro-oxic conditions, indicating oxygen is necessary for its denitrification process. This contrasts with typical anaerobic denitrifiers.

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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

Published on: October 7, 2020

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors
07:59

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors

Published on: December 6, 2018

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Last Updated: May 27, 2026

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti
20:01

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti

Published on: October 1, 2013

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
08:05

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

Published on: October 7, 2020

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors
07:59

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors

Published on: December 6, 2018

Area of Science:

  • Microbiology
  • Environmental Science
  • Biochemistry

Background:

  • Denitrification is the microbial reduction of nitrate to nitrogen gas (N2).
  • Bradyrhizobium japonicum utilizes napEDABC, nirK, norCBQD, and nosRZDFYLX genes for denitrification.
  • Sinorhizobium meliloti possesses homologous genes for denitrification on its symbiotic plasmid pSymA.

Purpose of the Study:

  • To investigate the denitrification capabilities of Sinorhizobium meliloti under varying oxygen conditions.
  • To clarify the role of oxygen in S. meliloti's denitrification process.
  • To provide insights into the regulation of S. meliloti denitrification genes.

Main Methods:

  • Whole-genome transcriptomic analyses to study gene expression under micro-oxic conditions.
  • Assessing S. meliloti's growth and denitrifying activity in free-living and symbiotic forms.
  • Experimental validation of respiratory substrate utilization under micro-oxic conditions.

Main Results:

  • S. meliloti denitrification genes are induced under micro-oxic conditions.
  • S. meliloti exhibits denitrifying activities in both free-living and symbiotic states.
  • S. meliloti grows using nitrate or nitrite as respiratory substrates specifically under micro-oxic conditions, requiring oxygen.

Conclusions:

  • Sinorhizobium meliloti is an oxygen-dependent denitrifier, unlike anaerobic denitrifiers.
  • Oxygen is essential for S. meliloti's denitrification, despite possessing a complete denitrification gene set.
  • Further understanding of S. meliloti denitrification gene regulation is warranted.