Soil Bacterial Consortia in Rhizobium–Legume Interactions

Since the existence of plant growth-promoting rhizobacteria (PGPR), the usage of consortia of several strains is being utilized for the development of bioinoculants. The existence of true commensal microorganisms in the complex ecosystem is hard to predict, even to isolate, where these are in the complex interactions. It is obvious to assume transitions of functions from synergistic to commensal one microorganism for other during interaction with their partner. These microorganisms may be considered helper bacteria, to establish or influence a successful interaction between two entities. In a more precise way, the helper bacteria can be called ‘tritagonists’, for example—as helper bacteria, free-living rhizobacteria support heroic rhizobia, which establish a symbiotic relationship with the legume. Where rhizobia fix atmospheric nitrogen during symbiotic interactions, the ‘tritagonist’ helps rhizobia in several ways, during plant interactions, niche stabilization, and environmental management. This chapter deals an exclusive story on the beneficial aspects of free-living rhizobia in the complex interactions between rhizobia and legumes. Understanding the hidden science of all natural phenomena via scientific study will certainly prove a contribution to agrobiology for the sustainable development and agriculture.