Rhizobial Extracellular Signaling Molecules and Their Functions in Symbiotic Interactions with Legumes
Rhizobia (symbiotic nitrogen-fixing soil bacteria) and their legume host plants communicate with each other via signaling molecules such as flavonoids and Nod factors. In addition, rhizobia use separate “quorum sensing” (QS) systems to communicate among themselves. QS systems in rhizobia have been implicated as regulators of plasmid transfer, nodulation efficiency, nitrogen fixation, polysaccharide production and degradation, swarming motility, stress adaptation, and biofilm formation. Most rhizobial species studied to date appear to utilize one or more acyl homoserine lactone (AHL)-based QS systems. This chapter summarizes our current knowledge of QS signaling molecules and their functions in rhizobia, particularly the widespread genera Sinorhizobium, Mesorhizobium, Rhizobium, and Bradyrhizobium.
KeywordsQuorum Sense Quorum Sense System Plasmid Transfer Acyl Homoserine Lactone Quorum Sense Signal
This review and studies by the author’s group described herein were supported by grants from the Secretaría de Ciencia y Técnica (UNRC), Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT), and Consejo Nacional de Investigaciones Científicas y Técnicas of the República Argentina (CONICET). WG is a Career Member of CONICET. Thanks to Dr. S. Anderson for English editing of the manuscript.
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