Azospirillum lipoferum
In agriculture Azospirillum lipoferum is used to promote root development and nitrogen fixation in various crops, leading to enhanced growth and higher agricultural productivity.
Strength
1 x 10⁸ CFU per gram / 1 x 10⁹ CFU per gram
Benefits
Disease Suppression
Suppresses soil-borne pathogens through competition for nutrients and production of antimicrobial compounds, enhancing plant health and reducing disease incidence.
Plant Growth Promotion
Produces plant growth-promoting substances like auxins and cytokinins, stimulating root growth and overall plant development.
Phosphate Solubilization
Releases phosphate bound in the soil, making it available for plant uptake, thereby improving phosphorus nutrition.
Nitrogen Fixation
Converts atmospheric nitrogen into ammonia, enhancing soil fertility and reducing the need for nitrogen fertilizers.
FAQ
1. What physiological mechanisms underlie the benefits of Azospirillum lipoferum in crops?
Azospirillum lipoferum is a diazotrophic bacterium that colonizes the rhizosphere and endorhizally associates with plant roots. Through biological nitrogen fixation via the nitrogenase enzyme complex, it converts atmospheric N₂ into bioavailable ammonia, enhancing plant nitrogen nutrition. Additionally, it synthesizes phytohormones (indole-3-acetic acid, gibberellins) that modulate root architecture—promoting lateral root proliferation and root hair elongation—thereby increasing absorptive surface area and nutrient uptake efficiency.
2. How is Azospirillum lipoferum formulated and applied in agronomic practice?
– Seed Inoculation: Prepare a peat-based carrier formulation containing ≥10⁸ CFU/g. Coat seeds at 10 g inoculant per kg seed, ensuring uniform adhesion with an adhesive such as sterile sucrose solution. Air-dry for 30–60 minutes prior to sowing. – Seedling Root Dip: Suspend 100 g of inoculum in 10 L of sterile water and dip root systems of nursery seedlings for 15 minutes before transplanting. – Soil Amendment: Incorporate 3–5 kg inoculant per hectare into the top 10 cm of soil, preferably mixed with well-decomposed organic manure. – Liquid Delivery: Dissolve 3 kg inoculant in 1,000 L of irrigation water and apply via drip or furrow irrigation systems to distribute cells throughout the rhizosphere.
3. Which agronomic crops demonstrate optimal responsiveness to Azospirillum lipoferum inoculation?
Field and greenhouse trials indicate significant yield and biomass improvements in Poaceae (wheat, maize, rice, sorghum), Fabaceae (pulses), Brassicaceae (oilseeds), Solanaceae (tomato, pepper), and Cucurbitaceae (cucumber, melon). Enhanced root development and N-use efficiency have been documented across cereals, legumes, oilseeds, horticultural, and fiber crops.
4. What compatibility and biosafety considerations apply to Azospirillum lipoferum applications?
Azospirillum lipoferum formulations are biosafe, exhibiting no pathogenicity to plants, humans, or animals. The bacterium is compatible with organic amendments, biofertilizers, and select biopesticides. Physical or chemical incompatibilities may arise when co-applied with high concentrations of synthetic fertilizers or broad-spectrum biocides; sequential rather than simultaneous application is recommended to maintain cell viability.
5. What are the recommended storage conditions and shelf life parameters for Azospirillum lipoferum inoculants?
Maintain formulations at 4–10 °C in moisture-proof, opaque packaging. Under these conditions, viable cell counts remain ≥10⁷ CFU/g for 9–12 months post-manufacture. Prolonged exposure to temperatures above 25 °C or high relative humidity reduces survival rates and inoculum efficacy.
Scientific References
1. Azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects
URL: https://academic.oup.com/femsre/article/24/4/487/510690
Journal: FEMS Microbiology Reviews (2000)
2. Azospirillum: benefits that go far beyond biological nitrogen fixation
URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC5935603/
Journal: PMC - PubMed Central (2018)
3. Field-based assessment of the mechanism of maize yield enhancement by Azospirillum lipoferum CRT1
URL: https://www.nature.com/articles/s41598-017-07929-8
Journal: Scientific Reports - Nature (2017)
4. Posttranslational regulation of nitrogenase activity in Azospirillum brasilense
URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC196782/
Journal: Journal of Bacteriology
5. Molecular Mechanisms Determining the Role of Bacteria from the Genus Azospirillum in Plant Growth Promotion
URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC10252715/Journal: International Journal of Molecular Sciences (2023)
Mode of Action
Biological Nitrogen Fixation Mechanism
Azospirillum lipoferum converts atmospheric nitrogen (N₂) into ammonium (NH₄⁺) under microaerobic conditions through the nitrogenase enzyme complex. This complex consists of two essential components: the dinitrogenase protein (MoFe protein, NifDK) containing a molybdenum-iron cofactor where N₂ reduction occurs, and the dinitrogenase reductase protein (Fe protein, NifH) that transfers electrons to the nitrogenase protein.
The efficiency of nitrogen fixation in A. lipoferum reaches 48 mg total nitrogen per gram glucose consumed at late log phase, with approximately 25% of fixed nitrogen recovered in culture supernatants. This bacterium demonstrates a unique hydrogenase system - an active uptake hydrogenase that increases during glucose limitation and serves as an oxygen protection mechanism for the oxygen-sensitive nitrogenase.
Molecular Regulation Systems
Transcriptional Control
The nitrogen fixation process is regulated by multiple nif genes including the nifHDK operon encoding nitrogenase components and nifA as the transcriptional activator. Expression is controlled by the general nitrogen regulatory system involving NtrBC proteins and the alternative sigma factor σ⁵⁴ (RpoN).
Post-translational Regulation
A. lipoferum employs reversible ADP-ribosylation of the nitrogenase iron protein mediated by DraT (ADP-ribosyltransferase) and DraG (activating glycohydrolase) enzymes. This mechanism provides rapid response to environmental changes - nitrogenase becomes inactive when ADP-ribosylated in the presence of ammonium or anaerobic conditions, and reactivated when ADP-ribosyl groups are removed.
Plant Growth Promotion Mechanisms
Phytohormone Production
A. lipoferum synthesizes multiple plant hormones through distinct biosynthetic pathways. The bacterium produces indole-3-acetic acid (IAA) via the indole-3-pyruvate (IPyA) pathway using the key enzyme indole-3-pyruvate decarboxylase encoded by ipdC. It also demonstrates capacity for gibberellin metabolism, effectively hydrolyzing GA₂₀-glucosyl conjugates and performing 3β-hydroxylation to convert GA₂₀ to the bioactive GA₁.
The bacterium expresses ACC deaminase which hydrolyzes the ethylene precursor 1-aminocyclopropane-1-carboxylate, reducing plant ethylene levels and promoting growth. Additional hormones include cytokinins through octaprenyl diphosphate synthase activity.
Root System Architecture Modification
Inoculation with A. lipoferum results in altered root morphology characterized by increased lateral root formation and enhanced root hair development. This root system expansion allows plants to explore larger soil volumes for nutrient and water acquisition. Field studies demonstrate that these morphological changes occur early in plant development and correlate with improved photosynthetic potential and reduced glucose content in ascending sap.
Root Colonization and Plant Interaction
Attachment Mechanisms
A. lipoferum employs a two-step colonization process. Initial adsorption is mediated by the polar flagellum, whose flagellin protein is a glycoprotein essential for motility-dependent attachment. The subsequent anchoring phase involves unidentified surface polysaccharides that facilitate stable root surface colonization.
Energy taxis plays a crucial role in root colonization, with bacteria navigating toward metabolizable compounds in root exudates. This chemotactic response contributes to the broad host range observed in Azospirillum-plant associations.
Mineral Nutrition Enhancement
A. lipoferum demonstrates phosphate solubilization ability, though weaker than specialized phosphate-solubilizing bacteria. The mechanism involves organic acid production (primarily acetic acid) that reduces medium pH and releases soluble phosphate from calcium phosphate complexes. Coimmobilization with other phosphate-solubilizing bacteria like Bacillus megaterium significantly enhances phosphate availability.
The bacterium also participates in iron nutrition through potential siderophore production and iron chelation mechanisms , though specific iron acquisition systems require further characterization.
Agricultural Applications and Field Performance
Commercial Inoculant Effectiveness
Field studies with commercial strain A. lipoferum CRT1 demonstrate variable but significant yield enhancement across different agricultural sites. The bacterium's effectiveness depends on soil characteristics and environmental conditions, with survival on maize roots limited to approximately 57 days post-inoculation.
Research indicates that A. lipoferum inoculation can substitute for 50% of nitrogen fertilizer applications without yield reduction , demonstrating potential for sustainable agriculture practices. The bacterium shows particular efficacy when applied as seed coating formulations.
Stress Tolerance Mechanisms
A. lipoferum confers drought tolerance through multiple mechanisms including abscisic acid synthesis, osmotic adjustment, and antioxidant enzyme activation. The bacterium induces expression of stress-related genes and enhances water use efficiency in treated plants.
Additional Info
Recommended Crops: Cereals, Millets, Pulses, Oilseeds, Fibre Crops, Sugar Crops, Forage Crops, Plantation crops, Vegetables, Fruits, Spices, Flowers, Medicinal crops, Aromatic Crops, Orchards, and Ornamentals.
Compatibility: Compatible with Bio Pesticides, Bio Fertilizers, and Plant growth hormones but not with chemical fertilizers and chemical pesticides.
Shelf Life: Stable within 1 year from the date of manufacturing.
Packing: We offer tailor-made packaging as per customers' requirements.
Dosage & Application
Seed Coating/Seed Treatment: Coat 1 kg of seeds with a slurry mixture of 10 g of Azospirillum Lipoferum and 10 g of crude sugar in sufficient water. Dry the coated seeds in shade before sowing or broadcasting in the field.
Seedling Treatment: Dip seedlings into a mixture of 100 grams of Azospirillum Lipoferum with sufficient water.
Soil Treatment: Mix 3-5 kg per acre of Azospirillum Lipoferum with organic manure or fertilizers. Incorporate into the soil during planting or sowing.
Irrigation: Mix 3 kg per acre of Azospirillum Lipoferum in water and apply through drip lines.
