title: The symbiotic biofilm of Sinorhizobium fredii SMH12, necessary for successful colonization and symbiosis of Glycine max cv Osumi, is regulated by Quorum Sensing systems and inducing flavonoids via NodD1.
abstract: Bacterial surface components, especially exopolysaccharides, in combination with bacterial Quorum Sensing signals are crucial for the formation of biofilms in most species studied so far. Biofilm formation allows soil bacteria to colonize their surrounding habitat and survive common environmental stresses such as desiccation and nutrient limitation. This mode of life is often essential for survival in bacteria of the genera Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Rhizobium. The role of biofilm formation in symbiosis has been investigated in detail for Sinorhizobium meliloti and Bradyrhizobium japonicum. However, for S. fredii this process has not been studied. In this work we have demonstrated that biofilm formation is crucial for an optimal root colonization and symbiosis between S. fredii SMH12 and Glycine max cv Osumi. In this bacterium, nod-gene inducing flavonoids and the NodD1 protein are required for the transition of the biofilm structure from monolayer to microcolony. Quorum Sensing systems are also required for the full development of both types of biofilms. In fact, both the nodD1 mutant and the lactonase strain (the lactonase enzyme prevents AHL accumulation) are defective in soybean root colonization. The impairment of the lactonase strain in its colonization ability leads to a decrease in the symbiotic parameters. Interestingly, NodD1 together with flavonoids activates certain quorum sensing systems implicit in the development of the symbiotic biofilm. Thus, S. fredii SMH12 by means of a unique key molecule, the flavonoid, efficiently forms biofilm, colonizes the legume roots and activates the synthesis of Nod factors, required for successfully symbiosis.
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Pérez-Montaño
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Jiménez-Guerrero
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Del Cerro
authors.affiliation: Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Baena-Ropero
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: López-Baena
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Ollero
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Bellogín
authors.affiliation: Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Lloret
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Espuny
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms; D005419:Flavonoids / Q000096:biosynthesis*; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D053038:Quorum Sensing; D042181:Sinorhizobium fredii / Q000502:physiology*; D013025:Glycine max / Q000382:microbiology*; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D005419:Flavonoids