Indole-3-acetic acid (IAA), the major natural auxin, is produced not only by plants but also by many rhizosphere and endophytic bacteria. A 2024 Microbiological Research review summarizes bacterial IAA biosynthesis and its roles in plant–microbe interactions.
Multiple bacterial IAA pathways
Bacteria can synthesize IAA through indole-3-pyruvic acid (IPyA), indole-3-acetamide (IAM) and other pathways whose activity depends on strain and environment.
IAA is not simply a plant-growth drug
Bacterial IAA can alter root elongation, lateral roots and root hairs, affecting nutrient uptake and stress responses. Effects are strongly concentration-dependent, and excessive auxin signaling can inhibit growth. Pathogens can also manipulate host IAA dynamics.
Agricultural use requires more than high IAA production
An IAA-producing strain must colonize the target crop, persist under field conditions and interact safely with the resident microbiome. Persistence across seasons cannot be assumed.
The practical opportunity is therefore microbial management of hormone signaling, not simply adding “natural auxin” to soil.
For related context, see How Many Plant Hormones Are in Compost? LC–MS Found Up to 35 Compounds Across Six Materials.
For related context, see Crop Diversification Reshapes Peanut Root Exudates and Soil Microbes to Increase Nitrogen Fixation.
For related context, see Turmeric-Leaf Seed Priming Raised Chickpea Germination to 94.5% and Field Yield by Up to 16%.
Reference
- Etesami H, Glick BR. Bacterial indole-3-acetic acid: A key regulator for plant growth, plant-microbe interactions, and agricultural adaptive resilience. Microbiological Research. 2024;281:127602. https://doi.org/10.1016/j.micres.2024.127602
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