Plant Growth-Promoting Bacteria: Mechanisms and Applications

Plant Growth-Promoting Bacteria

With increasing human population, global food production at the current rate would be insufficient to meet the dietary needs of all the people in the near future. It is, therefore, important to boost agricultural productivity in the next few decades. Also, a sustainable and environment-friendly approach is necessary to prevent the exploitation of natural resources. Plant Growth Promoting Bacteria or PGPB can help in achieving the dual goal of crop productivity and sustainable agriculture.

Plant Growth Promoting Bacteria

It is well known today that soil is replete with different forms of microorganisms. Of these, bacteria is the most common. According to the scientific data, soil host millions of bacteria. It is influenced by soil conditions such as temperature, moisture, salt and types of plants found in the soil.

It is important to note that bacteria is highly-concentrated around the roots of the plant. This narrow region in the soil is known as the rhizosphere. The plant growth-promoting bacteria belong to the beneficial and heterogeneous group of microorganisms in the rhizosphere that is capable of stimulating plant growth. Moreover, it protects against diseases and abiotic stresses by controlling or inhibiting the activity of pathogens. Furthermore, it improves soil structure as well.

Depending on the plant species and strains, the influence of bacteria on plant growth and its mechanism differs. The mechanisms are broadly classified as Direct and Indirect.  The indirect mechanism involves activation of defence mechanism against diseases, also known as induced systematic resistance – ISR.

Direct Mechanism

A direct mechanism includes plant growth by increasing the nutrient supply and hormones to the plant.


Bio-fertilizer consists of microorganisms which are applied to seeds, plant surfaces and soil to increase the supply of nutrients and help in plant growth. Different microorganism present in bio-fertilizer boosts soil fertility, natural soil nutrient cycle and soil organic matter availability. PGPB are one of the most widely-used beneficial bacteria today.

Nitrogen fixation – Nitrogen fixation is the process in which atmospheric nitrogen is converted into a usable form that changes into ammonia. It is the basic building block of plants. Biological nitrogen fixation is carried out by microorganisms in nature. A wide variety of plant growth-promoting bacterial species helps in plant growth and better yield by boosting nitrogen intake by plants.

Phosphate Solubilization – Phosphorus is an essential nutrient for optimal plant growth. But phosphorus is available mostly in insoluble forms. The PGPB helps in solubilization of inorganic phosphorus and mineralization of organic phosphorus. As phosphate fertilizer is too expensive for farmers, using plant growth-promoting bacteria as inoculum for phosphate intake is advantageous.

Iron is another nutrient which is scarce in soil. PGPB can produce compounds known as siderophores which contain ferric iron. Roots can take this and use it for plant growth.

Phytohormones – Phytohormones play a major role in the natural growth of plants. Different processes like leaf formation, flower development and fruit ripening are regulated and determined by it. Due to various environmental factors, plants are subjected to stress. This is where PGPB can alter phytohormone levels and help in its response to stress.

Indirect Mechanism

Induced Systemic Resistance – Induced systemic resistance is a phenomenon or form of defence mechanism in plants that activates when a pathogenic agent infects plants. It helps in controlling diseases. The inducing bacteria triggers a reaction in the roots which acts as a signal that reaches all parts of the plant for induction of systematic resistance.

Today, agricultural depends solely on chemical inputs for boosting plant growth and crop protection. But the overuse of chemicals can cause unanticipated environmental problems. Therefore, there is an urgent need for using plant growth-promoting solutions for sustainable agriculture without any environmental issues.

Organica Biotech is one of the leading companies with a wide range of solutions for sustainable agriculture. It’s Magic Gro range of products include Magic Gro Drip Sol, Magic Gro Nemacare, Magic Gro PSB and other products which boost crop development, improve plant immunity and vigour sustainably.

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