Background: Bacterium-based fertilizers are functional bio-inoculants comprised different types of soil bacteria widely used for enhancing the growth of plants. The bacterial strains used for crafting biofertilizers mainly isolated from agricultural soils showed potential plant-growth-promoting traits and could enhance the quality of plant root system development and differentiation.
Methods: Up to date, various types of Gram-positive and negative bacterial isolates were characterized that showed differential plant-growth-promoting properties. The only challenge with these strains is that most of PGPRs might lose their functionality after isolation from soil layers, therefore leading to a significant decrease in their biological activity. The application of biotechnological methods for enhancing the gene expression profile of such bacteria can regenerate their potential for regaining their acknowledged properties to affect plant growth. In the case of medicinal plants, lower production of vegetative sections might affect the total synthesis of useful secondary metabolites used for different proposes. Therefore, enriching the soil rhizosphere around root system of medicinal plants using exotic bacteria may change the rate of their growth and metabolite production.
Results: The current literature suggested that various types of PGPRs could produce phytohormones like auxin to enhance the growth of plants. Indeed, these strains are also able to provide extra level of natural nutrient in the nearby of medicinal plant roots and therefore have the potential to guarantee their sustainable growth within harsh environment. In this respect, understanding the interaction between medicinal plants root system and soil rhizobacteria can open a new window for engineering different types of PGPRs for medicinal production.
Conclusion: In this review, the current trends on the biotechnological advancements for improving plant-growth-promoting traits of soil bacteria will be discussed and possible routes for re-introduce effective isolates into soil were reviewed.