[Quorum sensing involved in the regulation of secondary metabolism in streptomycetes--a review].

Quorum sensing as an extracellular signal transduction system is distributed widely among many bacteria to coordinate their behaviors or actions by mediating gene expression, and plays key roles in many physiological processes and pathogenicity. Quorum sensing was also observed among many streptomycetes, as an important regulatory mechanism of secondary metabolite biosynthesis and/or cell differentiation, and displayed certain diversity of the autoinducer structures and action mechanisms. The participation of A-factor-driven quorum sensing systems in the secondary metabolism has been extensively studied, and triggered the identification of a major signal class featured with gamma-butyrolactone core. Additionally, PI-factor, M-factor and certain small antibiotic molecules recently found in streptomycetes clearly could play important roles in the biosynthetic pathways of some antibiotics, and might represent extracellular autoinducer classes with novel structures. Meanwhile, some specific products of streptomycetes including cholesterol oxidase and glycerol have been identified to function as cell-signaling molecules which modulate the secondary metabolic activities in streptomycetes, probably by the mode of quorum sensing. Here, we reviewed research advances on quorum sensing systems involved in the accumulation of secondary metabolites in streptomycetes, mainly focusing on the clarification of their action modes and structural diversity of autoinducers. We also prospected the research trends in this field and application of autoinducers through quorum-sensing in metabolic engineering of natural products.