Related Experiment Video
Updated: May 30, 2026
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
Phylogenetic perspectives of nitrogen-fixing actinobacteria
Maher Gtari1, Faten Ghodhbane-Gtari, Imen Nouioui
1Laboratoire Microorganismes and Biomolécules Actives, Université de Tunis El Manar (FST) et Université de Carthage (ISSTE), 2092, Tunis, Tunisia. maher.gtari@fst.rnu.tn
Archives of Microbiology
|July 23, 2011
Summary
Diazotrophy, the ability to fix atmospheric nitrogen, is increasingly found in actinobacteria beyond the Frankia genus. Phylogenetic analysis of nitrogen fixation (nifH) genes is crucial for understanding the evolution of this trait in actinobacteria.
Area of Science:
- Microbiology
- Evolutionary Biology
- Genetics
Background:
- Diazotrophy was historically confined to the Frankia genus within actinobacteria.
- Recent discoveries show nitrogen fixation (nifH) genes in diverse non-Frankia actinobacteria, challenging this view.
- Reports of nitrogenase activity and nifH genes in genera like Mycobacterium, Corynebacterium, Arthrobacter, Agromyces, and Micromonospora are expanding.
Purpose of the Study:
- To investigate the evolutionary history and emergence of diazotrophy among actinobacteria.
- To conduct a phylogenetic comparison of nitrogen fixation (nifH) genes within actinobacteria.
- To explore the distribution and potential functional significance of nifH genes in non-Frankia actinobacteria.
Main Methods:
- Phylogenetic analysis of nitrogen fixation (nifH) genes.
- Review of existing literature on nitrogenase activity and nifH gene identification in actinobacteria.
- Analysis of draft genome sequences for nifH-like sequences.
Main Results:
- Numerous nifH genes have been identified in various actinobacteria genera outside of Frankia.
- Nitrogen fixation has been demonstrated through multiple methods including growth on nitrogen-free media and acetylene reduction assays.
- Genome sequencing revealed nifH-like sequences in species like Slackia exigua, Rothia mucilaginosa, and Gordonibacter pamelaeae.
Conclusions:
- The ability for diazotrophy appears more widespread in actinobacteria than previously thought.
- The presence of nifH sequences does not guarantee functional nitrogen fixation; further research is needed.
- Investigating the evolutionary origins (vertical vs. horizontal gene transfer) of nifH genes is essential.
Related Concept Videos
01:22Inorganic 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...
01:30Bacterial Phylum Actinobacteria
Coryneform bacteria are gram-positive, aerobic, nonmotile rods that exhibit irregular, club-shaped, or V-shaped arrangements. Their V-shape results from snapping division, where the inner cell wall layer forms the cross-wall, while the outer layer remains intact until it ruptures on one side, causing the daughter cells to bend away.The primary genera are Corynebacterium and Arthrobacter. Corynebacterium includes diverse species, ranging from saprophytes to pathogens like Corynebacterium...
01:26Microbes 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...
02:11The Roles of Bacteria and Fungi in Plant Nutrition
Plants have the impressive ability to create their own food through photosynthesis. However, plants often require assistance from organisms in the soil to acquire the nutrients they need to function correctly. Both bacteria and fungi have evolved symbiotic relationships with plants that help the species to thrive in a wide variety of environments.
01:20Overview 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 largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this nitrogen...
01:24Diversity of Archaea II
Archaea, one of the three domains of life, exhibit remarkable diversity and adaptability, thriving in both extreme and moderate environments. Historically, most identified archaea have been classified into two major phyla: Euryarchaeota and Crenarchaeota. However, recent molecular studies have expanded this classification to include three additional phyla: Thaumarchaeota, Nanoarchaeota, and Korarchaeota, each exhibiting unique characteristics and ecological roles.Thaumarchaeota: Mesophiles...