Related Experiment Video
Updated: May 15, 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
Characterization of nitrate and nitrite utilization system in Rhodococcus jostii RHA1
Toju Iino1, Keisuke Miyauchi, Daisuke Kasai
1Department of Bioengineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188, Japan.
Journal of Bioscience and Bioengineering
|January 9, 2013
Summary
Rhodococcus jostii RHA1 utilizes nitrate and nitrite via nirB1, nirB2, and narK genes for soil remediation. Ammonium represses these genes, indicating a unique nitrogen metabolism crucial for soil growth.
Area of Science:
- Environmental microbiology
- Bioremediation
- Bacterial nitrogen metabolism
Background:
- Rhodococcus jostii RHA1 is a polychlorinated-biphenyl degrader with potential for soil remediation.
- Genes narK (nitrate/nitrite transporter) and ro06366 (nitrite reductase) are upregulated in RHA1 during growth in sterile soil.
Purpose of the Study:
- Characterize narK, ro06366 (nirB1), and its paralog ro00862 (nirB2) to understand nitrate and nitrite utilization in RHA1.
- Investigate the role of these genes in RHA1's nitrogen metabolism and soil growth.
Main Methods:
- Quantitative reverse transcription PCR (qRT-PCR) to assess gene transcriptional induction.
- Construction and analysis of gene deletion mutants (single and double) to evaluate growth on nitrate/nitrite.
- Growth assays using various nitrogen sources.
Main Results:
- nirB1 and nirB2 expression is induced by nitrate or nitrite.
- Deletion mutants DnirB1 and DnirB2 show impaired growth on nitrate/nitrite; the double mutant Dnit cannot utilize either.
- DnarK mutant shows no growth on nitrate and reduced growth on nitrite, indicating narK's role in nitrate and nitrite uptake.
- Ammonium (≥3 mM) represses nirB1, nirB2, and narK transcription.
Conclusions:
- nirB1 and nirB2 are essential for nitrate and nitrite utilization in RHA1.
- narK is crucial for nitrate uptake and partially involved in nitrite uptake.
- RHA1 possesses a unique nitrogen metabolism system regulated by ammonium, vital for its soil growth and potential bioremediation applications.
More Related Videos
12:47Workflow Based on the Combination of Isotopic Tracer Experiments to Investigate Microbial Metabolism of Multiple Nutrient Sources
Published on: January 22, 2018
08:03A Tandem Liquid Chromatography–Mass Spectrometry-based Approach for Metabolite Analysis of Staphylococcus aureus
Published on: March 28, 2017
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...
01:28Anoxygenic Phototrophic Bacteria
Anoxygenic phototrophic bacteria are a diverse group of microorganisms that perform photosynthesis without producing oxygen. They primarily include purple sulfur bacteria, purple nonsulfur bacteria, green sulfur bacteria, and green nonsulfur bacteria. These bacteria are classified into the Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Chlorobi, and Chloroflexi lineages, each with distinct physiological and ecological adaptations.Purple sulfur bacteria belong to the...
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...
01:28Microbial Nutrition
Organisms exhibit remarkable metabolic diversity, categorized based on how they acquire energy and carbon. These strategies enable survival in various ecological niches and are essential for maintaining energy flow and nutrient cycling within ecosystems.Energy and Carbon SourcesOrganisms are classified as phototrophs or chemotrophs based on energy acquisition. Phototrophs use light as their energy source, while chemotrophs rely on oxidizing chemical compounds. Further differentiation arises...
01:15Metabolism 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...
01:28Carbon-dioxide Fixation
Carbon dioxide fixation in prokaryotes enables the assimilation of inorganic carbon into organic molecules, supporting biosynthetic pathways, sustaining ecosystems, and contributing to the global carbon cycle. It also has industrial applications in carbon capture and bioproduct synthesis. Autotrophic organisms rely on this process to utilize CO₂ as a carbon source in diverse environments.The Calvin CycleThe Calvin cycle is the most widespread carbon fixation mechanism, primarily used by...