Current Perspectives on Rhizobacterial-EPS interactions in Alleviation of Stress Responses: Novel Strategies for Sustainable Agricultural Productivity

Rhizobacterial exopolysaccharides (EPSs) are the active constituents of soil organic matter which possess numerous biological functions, viz., biofilm development and survival, host colonization, and bacterial autoaggregation, including host specificity, quorum sensing, participation in early stages of host plant infection, signaling molecule during plant development, and most importantly protection from environmental stresses. These adverse conditions lead to negative environmental impacts and socioeconomic consequences such as reduction of crop productivity and soil fertility. However, environmental concerns related to these stresses motivate the scientists to find out environment-friendly approaches for sustainable agriculture. Interestingly the plant growth-promoting rhizobacteria (PGPR) have evolved with several biochemical mechanisms to cope with the environmental biotic and abiotic stressors, viz., plant pathogen defenses, metal, salt, and drought. This review presents the recent advances and applications made hitherto in understanding the biochemical mechanisms of rhizobacterial-EPS interactions alleviate stress responses and their role in major processes involved in phytoremediation, such as heavy metal detoxification, biocomplexation, bioaggregation, biosorption, and biosequestration. Interestingly these EPSs have rapidly emerged as a new and industrially important source of polymeric materials, which are gradually becoming economically competitive for crop productivity. Nevertheless future progress in understanding of PGPR, mechanisms of plant-microbe-EPS interactions, could facilitate their development as the reliable components in management of sustainable agricultural systems.