CYANOBACTERIAL BIOFERTILIZER-Nostoc, Anabaena, Hapalosiphon

Cyanobacterial biofertilizers are eco-friendly microbial fertilizers derived from photosynthetic microorganisms known as cyanobacteria (blue-green algae). Common genera include Anabaena, Nostoc, Tolypothrix, and Hapalosiphon. These microorganisms are capable of fixing atmospheric nitrogen (N₂) into ammonia (NH₃), a form readily available to plants, through specialized cells called heterocysts.

Cyanobacteria grow abundantly in moist, sunlit environments, especially in paddy fields, forming a symbiotic association with aquatic ferns like Azolla. The Azolla–Anabaena complex is one of the most effective natural nitrogen-fixing systems used in rice cultivation.
Cyanobacterial biofertilizers are often sold in powder, granule, or liquid form under trade names like Blue Green Algae Biofertilizer or Azolla–Anabaena Biofertilizer. They are packed in airtight pouches or boxes to maintain viability and are recommended by agricultural departments for paddy, wheat, and sugarcane cultivation.

Cyanobacterial biofertilizers play a crucial role in sustainable and organic agriculture by providing a natural nitrogen source, enhancing soil health, and supporting environmental conservation. Their regular use not only improves crop productivity but also helps in maintaining ecological balance.

1. CYANOBACTERIAL BIOFERTILIZER SUBMITTED BY:
T.K.Vijithra, II. M.Sc Microbiology, Sri parmakalyani College, Alwarkurichi. SUBMITTED TO:
Dr. S. VISWANATHAN, ASSOCIATE PROFESSOR, Sri Parmakalyani College Alwarkurichi

2. INTRODUCTION Cyanobacteria are a group of Gram-negative, oxygenic photosynthetic prokaryotes that contain chlorophyll a, phycocyanin, and phycoerythrin pigments. They perform oxygenic photosynthesis similar to plants and are capable of nitrogen fixation in specialized cells called heterocysts. Cyanobacterial biofertilizers are a sustainable agricultural tool that uses nitrogen-fixing blue-green algae to enhance soil fertility and plant growth These microorganisms convert atmospheric nitrogen into a form plants can use, improve soil structure, help retain moisture, and reduce erosion.

3. They are an environmentally friendly alternative or supplement to chemical fertilizers, primarily valued for their ability to fix atmospheric nitrogen and produce plant growth-promoting substances. Examples of Cyanobacteria Used as Biofertilizers: Commonly used nitrogen-fixing genera include: Anabaena Nostoc Aulosira Tolypothrix Cylindrospermum Calothrix nostoc Anabaena azollae Hapalosiphon

4. 🌿 TYPES OF CYANOBACTERIAL BIOFERTILIZERS Cyanobacterial biofertilizers are mainly classified based on how the cyanobacteria live and interact with plants or the environment. Free-Living Cyanobacteria These are independent organisms that live freely in soil or water without forming any symbiotic association. ✳ Examples : Anabaena ,Nostoc,Tolypothrix,Calothrix,Cylindrospermum, Hapalosiphon

5. Symbiotic Cyanobacteria Example: Anabaena azollae (symbiont in Azolla fern).
Azolla hosts Anabaena in its leaf cavities, forming a mutually beneficial relationship.
Used extensively in paddy cultivation as a green manure biofertilizer.

6. Nostoc Structure & Features : Filamentous, blue-green colonies enclosed in a gelatinous sheath. Contains vegetative cells and specialized nitrogen-fixing cells called heterocysts.Found in moist soils, rocks, rice fields, and symbiotically in plants like Anthoceros (a bryophyte). Habitat : Moist soils, symbiotic with plants like liverworts and lichens. Nitrogen Fixation : Nostoc fixes atmospheric nitrogen inside heterocysts under aerobic condition. The enzyme nitrogenase converts N₂ → NH₃ (ammonia), which is later transformed into amino acids and proteins.

7. Functions & Role : Fixes atmospheric nitrogen and releases it as ammonia, improving soil fertility. Adds organic carbon to the soil through photosynthesis. Improves soil texture, water retention, and microbial balance. Agricultural Importance : Used as a biofertilizer in rice paddies and dryland soils. Helps reclaim barren or saline soils. Prevents soil erosion by forming crusts on soil surfaces. Special Features Tolerates extreme conditions (dry, high salinity).Some species produce bioactive compounds useful in medicine and bioremediation.

8. Anabaena General Characteristics Filamentous cyanobacterium with intercalary heterocysts (present in between cells).Capable of oxygenic photosynthesis and biological nitrogen fixation. Can exist freely or in symbiotic associations (notably with Azolla and Cycas). Habitat Commonly found in freshwater ponds, moist soils, and paddy fields. Thrives in waterlogged rice fields where it forms a green mat on the water surface.

9. Functions Converts atmospheric nitrogen into ammonia (NH₃) via the nitrogenase enzyme in heterocysts. Releases nitrogenous compounds into the surrounding soil or plant roots. Produces plant growth hormones such as IAA (Indole Acetic Acid), gibberellins, and vitamins.Improves plant root and shoot development. Applications Used as a biofertilizer in rice cultivation (as pure culture or in Azolla–Anabaena combination).Reduces the need for synthetic nitrogen fertilizers by up to 25–50%.Enhances crop yield and soil health over long-term use. Special Features plays a key role in Azolla–Anabaena symbiosis, providing continuous nitrogen supply to rice fields.Some species are used in biohydrogen production and biotechnological research.

10. Hapalosiphon General Characteristics Branched, filamentous cyanobacterium with heterocysts. Exhibits true branching, unlike many other cyanobacteria. Performs both photosynthesis and nitrogen fixation. Habitat Found in moist soils, rocks, and freshwater ecosystems. Often colonizes nutrient-poor or degraded soils.

11. Functions Fixes atmospheric nitrogen into forms usable by plants.Improves soil fertility and organic matter. Contributes to carbon cycling through photosynthesis. Can survive under harsh conditions like high temperature or low nutrients. Applications Used as a biofertilizer in nutrient-deficient or degraded soils.Helps in reclaiming barren land and enhancing soil microbial activity.Studied for hydrogen gas production, bioremediation, and bioenergy development. Special Features Possesses biotechnological potential for renewable energy (biohydrogen, biofuel).Can be cultured easily and adapted to different environmental conditions.

12. Characteristics and Role: Nitrogen Fixation : This is the most significant benefit. Cyanobacteria, particularly those with specialized cells called heterocysts (e.g., Anabaena, Nostoc), can convert atmospheric nitrogen which plants cannot use, into usable forms like ammonium and nitrates This process is vital for plant nutrition. Plant Growth Promotion : They produce and excrete various secondary metabolites, including phytohormones (like auxins, cytokinins, and gibberellins), vitamins, and amino acids, which directly enhance seed germination, root growth, and overall plant development.

13. • Heterocystous Filamentous Structure Many cyanobacteria are filamentous (thread-like).
Some cells in the filament differentiate into heterocysts for nitrogen fixation (e.g., Anabaena, Nostoc).
• Free-Living or Symbiotic Exist as free-living forms in soil/water (Anabaena, Nostoc), or in symbiotic association with plants like Azolla and Cycas • Adaptability Can grow in diverse environments - fresh water, moist soil, paddy fields, and even in extreme conditions. Tolerant to high temperature and pH fluctuations. Growth-Promoting Substances Produce vitamins, amino acids, auxins, and gibberellins that enhance plant growth. Soil-Building and Organic Matter Formation Contribute to soil aggregation, improve soil structure, and increase organic carbon content. Eco-Friendly and Self-Sustaining Non-polluting and renewable source of nutrients. Reduce dependency on synthetic nitrogen fertilizers.

14. PRODUCTION OF CYANOBACTERIAL BIOFERTILIZER Cyanobacterial biofertilizers are produced using specific strains of nitrogen-fixing cyanobacteria such as Anabaena, Nostoc, Aulosira, and Tolypothrix.
They are mass-cultured under controlled conditions to obtain large quantities for agricultural use — especially in paddy fields. Selection of Strain Select efficient nitrogen-fixing strains of cyanobacteria (e.g., Anabaena, Nostoc, Aulosira).The chosen species should be:Fast-growingResistant to high temperature and sunlight Effective nitrogen fixers Able to multiply under field conditions

15. Preparation of Culture Medium The growth medium usually used is BG-11 medium or nitrogen-free medium (like Allen and Arnon medium).
Components include:
Phosphates Sulphates Trace elements Carbon source (like sodium bicarbonate)
The pH is adjusted to around 7.0–7.5. Inoculation and Laboratory Cultivation The selected strain is inoculated into flasks or bottles containing the culture medium.Maintained under sunlight or fluorescent light for photosynthesis.Temperature: 25–35°CpH: 7.0–8.0Duration: 7–10 days until dense green growth appears.

16. Mass Multiplication (Outdoor Cultivation) Tray Method : Shallow trays/tanks filled with 10–15 cm soil and water.Add nutrients: superphosphate (150 g/10 m²), Na₂CO₃ (50 g/10 m²).Spread inoculum evenly. Sunlight exposure for 10–15 days. Thick bluish-green mat forms on the surface Field/Tank Method Large pits or lined fields filled with soil-water mixture. Inoculum added and grown 10–15 days. Dense mat of cyanobacteria develops. Harvesting

When the cyanobacteria form a thick mat, water is drained off slowly.The mat is collected and dried in the sun for 2–3 days.
Dried flakes are then crushed into powder.

17. Packaging and Storage Packed in polyethylene bags (1–5 kg each). Stored in a cool, dry place away from sunlight. Shelf life: 3–6 months under proper storage. Field Application Applied mainly in rice (paddy) cultivation Recommended dose: 10–12 kg/ha of dry inoculum.Can be applied directly in flooded fields or mixed with water for broadcasting. Provides about 20–30 kg nitrogen per hectare per crop season.

18. Soil Application: Dried algal flakes or powder of cyanobacteria are mixed with water and spread over the field. Azolla–Anabaena Method: Azolla is grown on the water surface in rice fields before or after transplanting.
It multiplies and covers the water surface; when decomposed, it releases nitrogen into the soil Seed Treatment and Nursery Application:
Cyanobacterial inoculum can also be applied to nursery beds to ensure early nitrogen availability. Method of Application

19. Benefits of cyanobacteria using as biofertilizer.

20. Reduction of Chemical Fertilizer Use Chemical fertilizers (like urea and ammonium nitrate) release harmful gases such as nitrous oxide (a greenhouse gas).
Cyanobacteria fix atmospheric nitrogen biologically, thus reducing dependence on synthetic fertilizers.
This helps in preventing soil and water pollution caused by chemical runoff. Prevention of Water Pollution
Chemical fertilizers often leach into water bodies, causing eutrophication (excessive growth of algae and depletion of oxygen).
Cyanobacterial biofertilizers are biodegradable and do not release harmful chemicals, thereby protecting aquatic ecosystems. Environmental Importance of Cyanobacterial Biofertilizer

21. Reduction of Greenhouse Gas Emission

The biological nitrogen fixation by cyanobacteria avoids industrial processes (like the Haber–Bosch process) that emit large amounts of CO₂. Therefore, they help in climate change mitigation. Biodiversity Conservation

Cyanobacterial biofertilizers maintain microbial biodiversity in soil ecosystems.

They provide food and oxygen for other microorganisms, insects, and aquatic species, thus supporting ecological balance. Promotion of Sustainable and Organic Farming

Encourages organic agriculture by providing natural nutrients to plants. Supports sustainable farming practices that maintain long-term productivity without harming the environment. Reduces the carbon footprint of agriculture.

22. Benefits of Cyanobacterial Biofertilizers Eco-friendly – Reduces chemical fertilizer use and prevents soil pollution. Nitrogen Enrichment – Supplies biologically fixed nitrogen to crops. Improves Soil Structure – Enhances water-holding capacity and aeration. Cost-Effective – Low-cost and renewable fertilizer source. Enhances Crop Yield – Stimulates plant growth via hormones and vitamins. Supports Sustainable Agriculture – Long-term improvement in soil fertility. Carbon Sequestration – Absorbs CO₂ and contributes to climate regulation. Bioremediation – Removes heavy metals and pollutants from soil and water. Bioenergy Potential – Some species can produce biofuels and biohydrogen. Restores Degraded Soils – Useful in saline, alkaline, or nutrient-poor soils

23. Applications of Cyanobacterial Biofertilizer Cyanobacterial biofertilizers are widely used in agriculture, especially in rice cultivation, because of their ability to fix atmospheric nitrogen and improve soil fertility naturally. 🌿 In Paddy (Rice) Fields Cyanobacteria such as Anabaena, Nostoc, and Aulosira grow naturally in flooded rice fields. They fix atmospheric nitrogen and release it into the soil in a form available to rice plants. Regular use can reduce chemical nitrogen fertilizer requirements by 25–30%.The Azolla–Anabaena symbiotic system is especially effective in rice fields.

24. Soil Fertility Improvement: Cyanobacteria add organic matter and humus to the soil. They enhance soil texture, water-holding capacity, and microbial activity.Over time, they help maintain sustainable soil productivity. Reclamation of Wastelands and Saline Soil Certain cyanobacteria (like Nostoc and Phormidium) tolerate high salinity and poor soil conditions.Their growth helps in reclaiming barren and saline soils, making them fit for cultivation. Use in Azolla–Anabaena System Anabaena azollae lives symbiotically inside the fern Azolla.This combination is applied in rice fields as a green manure biofertilizer.
When Azolla decomposes, nitrogen fixed by Anabaena is released into the soil.

25. Eco-friendly Agriculture Reduces dependence on synthetic fertilizers and chemical pollution.
Promotes sustainable and organic farming.
Enhances biodiversity and soil microbial balance. Integrated Nutrient Management (INM) Cyanobacterial biofertilizers are often used along with other biofertilizers like Rhizobium or Azospirillum .This integrated approach maximizes nutrient use efficiency and crop yield. Enhances Crop Yield and Quality Provides essential nutrients to plants.
Stimulates growth through natural plant hormones (like auxins, vitamins).
Results in better crop yield and grain quality.

26. 📝 Nostoc , Anabaena , and Hapalosiphon are powerful cyanobacterial biofertilizers that naturally enrich the soil, enhance plant growth, and sustain agricultural productivity. They not only reduce dependency on chemical fertilizers but also maintain soil fertility and promote environmental protection. The integration of cyanobacterial biofertilizers in farming ensures long-term agricultural productivity and ecological balance. 📝CONCLUSION

27. TEACHING AND LEARNING IN ACTION T. K. VIJITHRA I I M.SC MICROBIOLOGY, PG AND RESEARCH DEPARTMENT OF MICROBIOLOGY, SRI PAR A MAKALYANI COLLEGE, ALWARKURICHI -627412

28. The King and the Spider A brave king once lost a battle and hid in a cave. Feeling hopeless, he saw a spider trying to weave its web. The spider fell many times but didn’t give up until it succeeded. The king learned from the spider’s patience and tried again to win his kingdom — this time, he won the battle. Moral : Try and try again until you succeed.