M. D. Huda Najeh Hassan
College of Applied Medical Sciences / Department of Medical Chemistry
Goal 15: Life on Land – Protect, restore, and promote the sustainable use of terrestrial ecosystems
https://sdgs.un.org/goals/goal15
Introduction
Nitrogen is an essential element for plant growth, as it is a fundamental component of amino acids, proteins, nucleic acids, and chlorophyll. Despite the abundance of atmospheric nitrogen gas (N₂), plants are unable to utilize it directly, which has led to extensive reliance on synthetic nitrogen fertilizers. However, excessive use of these fertilizers causes soil degradation, contamination of groundwater with nitrates, and increased emissions of nitrous oxide, one of the major greenhouse gases.
In this context, nitrogen-fixing bacteria have emerged as a sustainable biological alternative aligned with sustainable development, particularly in relation to food security and environmental protection.
Scientific Basis of Biological Nitrogen Fixation
Biological nitrogen fixation is defined as the conversion of atmospheric nitrogen gas (N₂) into ammonia (NH₃) by the enzyme nitrogenase. This process is carried out by specialized bacterial groups, either in symbiotic relationships with plants or as free-living organisms in the soil.
Major Nitrogen-Fixing Bacterial Genera
- Rhizobium: Lives symbiotically in the root nodules of leguminous plants.
- Azotobacter: A free-living bacterium capable of fixing nitrogen in aerobic soils.
- Azospirillum: Associates with cereal roots and enhances plant growth.
- Clostridium: Fixes nitrogen under anaerobic conditions.
These bacteria are characterized by the presence of nif genes responsible for the synthesis of the nitrogenase enzyme.
Importance of Isolating Local Strains
The efficiency of nitrogen-fixing bacteria depends on their adaptation to environmental conditions such as salinity, temperature, pH, and soil texture. Therefore, isolating local strains from agricultural soils offers several advantages:
- Tolerance to local environmental stresses (e.g., salinity or drought)
- Higher efficiency in symbiosis with local crops
- Reduced dependence on imported fertilizers
- Lower agricultural costs and improved long-term soil fertility
In semi-arid environments, such as many regions of Iraq, stress-tolerant strains—particularly those resistant to salinity—represent a strategic option for enhancing agricultural productivity.
Environmental and Economic Benefits
Environmentally: Reduction of nitrate pollution in water resources, decreased greenhouse gas emissions, and improvement of soil microbial structure.
Economically: Lower fertilizer costs, sustainably increased crop productivity, and support for organic agriculture.
Challenges and Future Perspectives
Key future challenges include the long-term stability of bacterial strains in soil, competition with native microbiota, the need for effective bioformulation techniques, and thorough biosafety evaluation before large-scale application.
Isolating nitrogen-fixing bacterial strains from local soils represents a strategic step toward reducing reliance on chemical fertilizers and achieving sustainable agriculture based on biological resources. Investment in environmental microbiological research not only enhances food security but also restores soil biological balance and reduces the environmental impact of agricultural activities.
The future of agriculture is moving toward intelligent systems that rely on beneficial microorganisms as a fundamental pillar of sustainable green production.
