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Related Concept Videos

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...
Microbes and the Nitrogen Cycle01:26

Microbes and the Nitrogen Cycle

The nitrogen cycle is a complex biogeochemical process critical to maintaining the balance of nitrogenous compounds in ecosystems. This cycle involves multiple microbial-mediated transformations through which nitrogen changes oxidation states, supporting essential ecological functions and contributing to plant and microbial growth.Nitrogen Fixation and AmmonificationNitrogen fixation initiates the cycle by converting inert atmospheric nitrogen (N₂) into bioavailable ammonia (NH₃), a process...
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...
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...
Microbial Mats01:25

Microbial Mats

Microbial communities forming biofilms and mats represent complex, spatially structured ecosystems where metabolic processes are stratified according to light, oxygen, and nutrient gradients. Biofilms are initial colonization stages, only a few millimeters thick, while mature microbial mats can reach centimeter-scale thickness and display intricate vertical organization. Their structural and functional heterogeneity allows microorganisms to occupy distinct ecological niches within a few...

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Related Experiment Video

Updated: Jul 14, 2026

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

Nitrifiers Drive Different N2O Production Patterns in Tropical River Sediments.

Dongdan Yuan1, Xiaoyu Cui2, Sibo Zhang3

  • 1School of Ecology, Hainan University, Haikou 570228, China.

Environmental Science & Technology
|July 13, 2026
PubMed
Summary

Tropical rivers are significant sources of nitrous oxide (N2O) emissions, with estuaries showing higher rates. Nitrifier denitrification, driven by specific bacteria, is the primary N2O production pathway, influenced by factors like salinity and nutrients.

Keywords:
15N−18O double tracerN2Oammonia-oxidizing bacteriacomplete ammonia-oxidizing bacteriametagenomic sequencingnitrifier denitrificationtropical rivers sediments

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Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems
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Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

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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

Related Experiment Videos

Last Updated: Jul 14, 2026

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

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems
09:38

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

Published on: October 29, 2016

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:

  • Environmental Science
  • Biogeochemistry
  • Climate Change Research

Background:

  • Global riverine nitrous oxide (N2O) emissions have quadrupled since the 20th century.
  • N2O emissions from tropical rivers remain poorly understood, despite their potential significance.

Purpose of the Study:

  • To investigate N2O flux, production rates, and mechanisms in China's tropical rivers.
  • To identify key microbial pathways and environmental factors controlling N2O production in these ecosystems.

Main Methods:

  • In situ N2O flux measurements using closed chambers.
  • Potential N2O production rates assessed with biological inhibitors and 15N-18O double tracer techniques.
  • Microbial community analysis via metagenomic sequencing and reverse transcription qPCR.

Main Results:

  • Hainan rivers exhibit high N2O flux and production rates, indicating they are significant emission hotspots.
  • Estuary samples showed significantly higher N2O flux and production rates compared to nonestuary samples.
  • Nitrifier denitrification (ND) was the dominant N2O production pathway, particularly in estuaries, involving specific ammonia-oxidizing bacteria and comammox.

Conclusions:

  • Tropical rivers, especially estuaries, are critical sources of N2O emissions.
  • Nitrifier denitrification is a key microbial process driving N2O production in these systems.
  • Management strategies focusing on ammonium fertilizer and estuary restoration are crucial for mitigating tropical river N2O emissions and global climate change.