Bacillus subtilis

Introduction

Bacillus subtilis is a widely used bacterium in agriculture known for promoting plant growth and protecting crops against fungal and bacterial diseases. As a resilient, spore-forming organism, it survives harsh soil conditions and establishes itself effectively in the rhizosphere. Its ability to produce antibiotics, enzymes, and growth regulators makes it a key microbe in both chemical-free and integrated farming systems.

Scientific Description

Bacillus subtilis is a gram-positive, rod-shaped, aerobic bacterium capable of forming endospores that enable it to survive in extreme conditions. It colonizes root surfaces and produces a wide spectrum of beneficial metabolites.

Key traits:

• Antibiosis: Produces lipopeptides (iturin, fengycin, surfactin) that inhibit fungal and bacterial pathogens.
• ISR Activation: Induces systemic resistance in plants against both root and foliar diseases.
• Phytohormone Production: Secretes auxins (e.g., IAA), cytokinins, and gibberellins that stimulate plant growth.
• Phosphate Solubilization & Enzyme Production: Helps mobilize nutrients and degrade organic matter in the rhizosphere.
• Spore-Forming: Long shelf life and high environmental stability — suitable for commercial formulations.

Benefits

• Suppresses Soil and Foliar Pathogens: Effective against Fusarium, Alternaria, Sclerotinia, Rhizoctonia, and more.
• Stimulates Root and Shoot Growth: Through auxin and cytokinin-like activity.
• Improves Nutrient Use Efficiency: Enhances phosphorus and micronutrient uptake.
• Compatible with Other Bioinputs: Can be used in combination with fungi, nitrogen fixers, and mycorrhiza.
• Shelf-Stable and Robust: One of the most resilient and storage-friendly biocontrol bacteria available.

Uses

• Crops Benefited: Rice, wheat, maize, cotton, tomato, brinjal, chili, groundnut, banana, sugarcane, pulses, and more.
• Application Methods:
  • Seed treatment: 4–10 g/kg seed
  • Soil application: 2–5 kg/acre with FYM or compost
  • Foliar spray: 0.5–1% solution for disease prevention
  • Drip irrigation: Suitable as a liquid formulation
• Best Timing: At sowing/transplant and before known disease windows (e.g., rainy season, flowering stage)
• Co-usage: Works synergistically with Trichoderma, Pseudomonas fluorescens, and phosphate solubilizers

Trivia

• Bacillus subtilis is considered a model organism in microbiology and biotechnology.
• Some formulations of B. subtilis are OMRI-listed (certified for organic use).
• Its spores can survive boiling and desiccation, making it ideal for industrial bioformulations.
• Also used in probiotics for animals and humans due to its safety and enzyme secretion profile.