Biofertilizer Bacteria: How Do Different Strains Boost Plant Growth?

Biofertilizers are substances that contain live microbial strains that colonize the rhizosphere and boost plant growth naturally by making a variety of nutrients available to it. They are cost-effective and environment-friendly alternatives to harmful chemical fertilizers for enhancing soil fertility.

Biofertilizer bacteria perform a variety of activities like nitrogen fixation, phosphorus solubilization, mobilization of micronutrients, helping the plant sustain and thrive against abiotic stresses, helping the root system absorb more plant nutrients and water, etc.

Let us take a look at some ways in which commonly used bacterial genera help the growth of plants.

Nutrient Uptake

When a plant is treated with biofertilizers, the microorganisms in it will form a close synergistic relationship with the root system, in what is called a “rhizosphere.” The rhizosphere is a specialized ecosystem that is formed around the plant roots. The microorganisms present in the rhizosphere help the plant through a variety of ways and in turn get rewarded by certain products (especially carbon sources) of the plant’s metabolism.

The most important activity of biofertilizer bacteria is making nutrients available to the plant. A variety of nutrients are required for the robust growth of the plant. Rhizosphere bacteria help in the following –

  • Nitrogen Fixation

Nitrogen is a vital nutrient. It is part of proteins (and enzymes) and the genetic material (DNA and RNA) of living organisms. While the atmosphere contains over 70% nitrogen, it is present in a form that is unavailable to the plants. Nitrogen fixing bacteria take up atmospheric nitrogen and convert it into nitrates, a form that is easily utilizable by plants.

Nitrogen fixers are of two types – symbiotic and free-living. Symbiotic nitrogen fixers live inside the roots of the leguminous plants in specialized structures called nodules. Free-living nitrogen-fixing bacteria, like Azotobacter, remain in the soil although they are in close contact with the root system, within the rhizosphere.

Many microbes of the Bacillus species like Bacillus subtilis, Bacillus licheniformis, Bacillus amyloliquifaciens, and Bacillus megaterium are known to be free-living nitrogen fixers that bring about plant growth promotion.

  • Phosphate Solubilization

Phosphorus is another vital nutrient required for the growth of the plant, especially in the bloom phase (flowering phase). Phosphorus is present in plentiful amounts in the soul, but again, most of it is present in a “bound” form, meaning it is unavailable to the plant. Phosphorus solubilizing bacteria free the bound phosphorus and make it readily available to the plants.

Phosphorus is the least available nutrient for plants as the majority of it is present in the form of insoluble and immovable inorganic phosphate. Phosphate solubilizing bacteria (PSB)produce organic acids like formic, lactic, etc., that solubilizes inorganic phosphate into a utilizable form. Some bacteria also produce enzymes called phosphatases that act on inorganic phosphates to break it down into a utilizable form.

Common phosphate solubilizing bacteria include Bacillus megaterium, Pseudomonas fluorescens, Paenibacillus polymyxa and Paenibacillus durum, among others.

  • Enhancing Iron Availability

Iron (ferrous compounds) is an important nutrient for the plant, the deficiency of which may result in abnormal metabolism and photosynthesis. The iron present in soils is usually found in a state that does not allow it to be easily taken up by plants.

Certain bacterial strains, like Pseudomonas and Bacillus, among others, produce compounds called siderophores that bind to unavailable ferrous compounds to create siderophore-iron compounds that can be easily taken up by the plants, thus making iron compounds readily available for plants.

Many other rhizosphere bacteria help in making potassium, sulfur and zinc available to the plants by secreting different metabolites.

Help Tolerate Abiotic Stress

Many plant growth-promoting rhizobacteria produce a wide variety of enzymes to help plants tolerate abiotic stresses. For example, certain rhizosphere bacteria are known to alleviate salinity stress in host plants by producing a variety of enzymes.

Organisms like Bacillus megaterium and Pseudomonas species are known to produce enzymes that help the plant tolerate different kinds of abiotic stresses.

King Crab – A Thoughtfully Developed Bioinoculant Supplement

So far, we have talked about the various ways in which many biofertilizer bacteria support plant growth, directly and indirectly. Biofertilizer bacteria are important constituents of the rhizosphere ecosystem that helps plants to thrive and enhance productivity.  

King Grab, from Plant Revolution, is a potent biofertilizer formulation that contains 11 strains of genera of beneficial bacteria like Bacillus, Pseudomonas and Paenibacillus. These include –

  • Bacillus subtilis  
  • Bacillus licheniformis
  • Bacillus amyloliquefaciens
  • Bacillus megaterium
  • Bacillus pumilus
  • Bacillus coagulans  
  • Bacillus azotoformans
  • Paenibacillus polymyxa
  • Paenibacillus durum  
  • Pseudomonas fluorescens
  • Pseudomonas aureofaciens
  • These are carefully selected strains of naturally occurring soil microorganisms that help the plant through different mechanisms. Soil inoculation with the King Crab supplement, as part of an organic fertilization program, will not only help the growth of the plant through easy nutrient availability from organic matter, but also protect the plants from abiotic stresses.

    Parting Thoughts

    A growing plant is a dynamic interplay of biological and chemical processes driven by not only the plant’s own metabolism but the combined metabolism of millions of microorganisms in the rhizosphere ecosystem. These symbionts play a vital role not only in ensuring the robust growth of the plant, but also in the conditioning of the soil and keeping it fertile, rich in biomass, and in good health for the future growth of plants.

    A shift towards using biofertilizers to support agriculture is in everyone’s favor – we are using an eco-friendly and sustainable support system for growing our plants for better crop yield and we are protecting ourselves and future generations from the harmful effects of synthetic agrochemicals through sustainable agriculture.