Related Experiment Video
Updated: Jun 5, 2026
07:59
Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors
Published on: December 6, 2018
Counteractive action of nitric oxide on the decrease of nitrogenase activity induced by enhanced ultraviolet-B
Lingui Xue1, Shiweng Li, Baoqin Zhang
1School of Chemistry and Bioengineering, Lanzhou Jiaotong University, Lanzhou 730070, People's Republic of China. xuelg@mail.lzjtu.cn
Current Microbiology
|December 29, 2010
Summary
Enhanced UV-B radiation damages Spirulina platensis 794 chlorophyll-a and nitrogenase. Nitric oxide (NO) and free radical scavengers like NAC counteract UV-B effects, protecting these vital cellular components.
Area of Science:
- Environmental Science
- Biotechnology
- Cyanobacteria Research
Background:
- Enhanced UV-B radiation poses a threat to aquatic ecosystems and photosynthetic organisms.
- Spirulina platensis 794, an N(2)-fixing cyanobacterium, is susceptible to UV-B induced damage.
- Understanding protective mechanisms against UV-B stress is crucial for algal biotechnology and environmental monitoring.
Purpose of the Study:
- To investigate the protective effects of nitric oxide (NO) and free radical scavengers against UV-B radiation damage in Spirulina platensis 794.
- To elucidate the impact of UV-B on key enzymes like nitrogenase and nitratase in cyanobacteria.
- To determine the role of reductant and ATP availability in UV-B inhibited nitrogenase activity.
Main Methods:
- Exposure of Spirulina platensis 794 cultures to enhanced UV-B radiation.
- Application of chemical treatments including sodium nitroprusside (SNP) as an NO donor and N-acetylcysteine (NAC) as a free radical scavenger.
- Measurement of chlorophyll-a integrity, nitrogenase activity, and nitratase activity under various treatment conditions.
Main Results:
- Enhanced UV-B radiation caused significant damage to chlorophyll-a and inhibited nitrogenase activity in a dose-dependent manner.
- Sodium nitroprusside (SNP) and NAC treatments markedly alleviated UV-B induced damage to chlorophyll-a and nitrogenase.
- UV-B stress led to specific inactivation of nitrogenase, which was not reversible by light, indicating a dependence on reductant and ATP supply.
Conclusions:
- Nitric oxide (NO) and free radical scavengers play a significant protective role against UV-B radiation damage in Spirulina platensis 794.
- Nitrogenase activity in cyanobacteria is critically dependent on a continuous supply of reductant and ATP.
- Enhanced UV-B radiation can increase nitratase activity, with synergistic effects observed when combined with SNP and NAC treatments.
Related Concept Videos
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...
01:28Nitric Oxide Signaling Pathway
Nitric oxide (NO), an inorganic gas, acts as a potent second messenger in most animal and plant tissues. NO diffuses out of the cells that produce it and enters the neighboring cells to generate a downstream response. NO synthase (NOS) catalyzes NO production by the deamination of the amino acid arginine. There are three isoforms of NOS. Endothelial cells have endothelial NOS (eNOS), nerve and muscle cells have neuronal NOS (nNOS), and macrophages produce inducible NOS (iNOS) upon exposure to...
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...
01:22Inorganic 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...
01:202° Amines to N-Nitrosamines: Reaction with NaNO2
Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
01:13meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...