ABSTRACT
ABSTRACT Scientists used to think that microorganisms, especially unicellular bacteria, are simple entities that function individually. However, research in the 1970s found that unicellular microorganisms use small signaling molecules, which function analogously to language, to determine their local population densities and to exhibit certain phenotypes. Collectively, the processes involved in the production and recognition of these signals (called autoinducers) are known as quorum sensing (QS). Using this form of cell-cell communication allows unicellular organisms to function as multicellular systems. Studies of QS systems in bacteria have also revealed that these bacterial languages can be intercepted, modulated, or destroyed by other organisms (quorum quenching [QQ]). The basic chemistry, biosynthesis, and mechanisms of autoinducers and types of QS systems contain an ocean of scientic information about how plants combat microbial infections. The inuence of QS systems in plant pathology, plant microbial interaction, and rhizosphere ecology has been well documented. QQ, also known as anti-QS, is a promising concept for plant disease-management programs. Several benecial microorganisms, such as Rhizobium, have been found to operate QS systems that govern plant-microbe interactions and symbiotic associations. This chapter, which contains a comprehensive overview of QS systems in bacteria, considers their mechanisms, autoinducers, QQ, and mechanisms of QQ, as well as applications of QS in biological control from the perspective of plant pathology.
