Quorum sensing in plant growth- promoting rhizobacteria and its impact on plant-microbe interaction

Abstract

Quorum sensing is a widespread mechanism in enormous number of bacteria for regulating various gene expression in a cell density-dependent manner through production and recognition of small molecules known as autoinducer. Diverse kinds of quorum-sensing networks are found in different bacterial species. Among various signal molecules, acyl homoserine lactone (AHL) signal molecules are the most and widely studied in bacteria. A number of simple to advanced techniques are being used to identify and characterize signal molecules. Production of signal molecules in a number of rhizospheric bacteria is documented. Rhizosphere is an active atmosphere where microbe-microbe and microbe-plant interaction is highest due to rich availability of nutrients provided in the form of root exudates. Several ecological and interdependent key characters of bacteria, like antibiotic, siderophore, or enzyme secretion, virulence factors of phytopathogens, as well as plant-microbe communications, are coordinated through quorum sensing (QS). In this chapter, we have provided brief fundamental aspects of quorum sensing and then addressed the recent trends on the significance of quorum sensing and signal molecules in microbe-microbe and microbe-plant interactions in the rhizosphere with special reference to plant growth-promoting rhizobacteria and plant health.