What Is Bacillus Velezensis and Its Role in Agriculture?

Bacillus velezensis is a species of bacteria found in soil and on plant surfaces across the globe. It belongs to a group of microorganisms recognized for beneficial relationships with plants. This bacterium is a Gram-positive, endospore-forming microbe, allowing it to survive harsh environmental conditions. Its widespread presence and non-pathogenic nature have made it a subject of interest in agricultural science.

Natural Habitat and Ecological Role

Bacillus velezensis thrives in natural settings like soil, water, and compost, but it is most frequently isolated from the area immediately surrounding plant roots. This zone, known as the rhizosphere, is a nutrient-rich environment where plants secrete sugars, amino acids, and other compounds. These secretions create a favorable habitat for microbes like B. velezensis.

In the rhizosphere, B. velezensis functions as a rhizobacterium, establishing a symbiotic relationship with plants. The bacterium colonizes root surfaces, forming a protective biofilm and feeding on nutrients from the plant’s root exudates. In return, the bacterium contributes to the health of the local soil environment, which indirectly benefits the host plant.

The ability to form endospores allows B. velezensis to persist in soil for long periods, enduring fluctuations in temperature, moisture, and nutrient availability. This resilience ensures its presence in diverse ecological niches, from agricultural fields to forests. Its adaptability and beneficial interactions with plants make it an important member of the soil microbiome.

Agricultural Applications

Bacillus velezensis is used in modern agriculture and horticulture, primarily as a biocontrol agent. As a biofungicide, it protects crops from a wide range of plant diseases. Farmers apply products containing B. velezensis to seeds, soil, or foliage to suppress pathogens. It is effective against diseases like Fusarium wilt, powdery mildew, and various root rots affecting vegetables, fruits, and ornamental plants.

Another application is its use as a plant growth-promoting rhizobacterium (PGPR), marketed as a biofertilizer. When colonizing plant roots, B. velezensis enhances nutrient uptake from the soil. It produces compounds that solubilize nutrients like phosphorus and potassium, making them more available for the plant to absorb. This process leads to improved plant vigor, better growth, and higher crop yields.

Its dual ability to protect plants and stimulate growth makes B. velezensis useful for integrated pest management (IPM) programs, reducing the need for synthetic chemicals. Strains like FZB42 are widely used in agricultural formulations for their proven efficacy. The use of B. velezensis is compatible with many conventional farming practices and is approved for organic agriculture.

Mechanisms of Plant Protection

Bacillus velezensis protects plants from pathogens through several mechanisms. One is the production of antimicrobial compounds. The bacterium synthesizes potent lipopeptides with strong antifungal and antibacterial properties. These include three major families—surfactins, iturins, and fengycins—which inhibit or kill pathogens by disrupting their cell membranes.

B. velezensis also engages in competition. By rapidly colonizing the surface of plant roots, a thriving population of the bacterium occupies space and consumes available nutrients. This process, known as competitive exclusion, creates a barrier that makes it difficult for harmful pathogens to establish themselves and infect the plant.

Another mechanism is its ability to trigger Induced Systemic Resistance (ISR) in the host plant. The presence of B. velezensis on the roots signals the plant to activate its own defense systems. This process “primes” the plant’s immune system, allowing it to respond more quickly to future attacks from pathogens or other stressors. This heightened state of alert is systemic, meaning the entire plant becomes more resistant to infection.

The activation of ISR involves signaling pathways within the plant, regulated by hormones like jasmonic acid and ethylene. Flagellin, a protein from the bacterium’s flagella, is one molecule the plant can recognize to initiate this defensive response.

Safety and Environmental Profile

Products containing Bacillus velezensis have a strong safety profile for humans, animals, and the environment. Regulatory agencies like the U.S. Environmental Protection Agency (EPA) have found strains of B. velezensis to be non-pathogenic and non-toxic to mammals. Acute toxicity studies in laboratory animals show no adverse effects from oral or inhalation exposure, allowing it to be applied without significant safety concerns for workers or consumers.

Environmentally, B. velezensis is a sustainable alternative to chemical fungicides and fertilizers. Unlike synthetic chemicals that can persist, harm beneficial insects, and contaminate soil and water, B. velezensis is a naturally occurring soil microorganism. Its application improves soil health and microbial diversity, and as a biological agent, it biodegrades without leaving harmful residues.

Due to its safety and environmental benefits, B. velezensis is widely approved for use in organic farming systems. Its adoption supports a food production system that is less reliant on synthetic inputs and has a smaller ecological footprint.