title: N-acyl-homoserine lactone-mediated quorum-sensing in Azospirillum: an exception rather than a rule.
abstract: Forty Azospirillum strains were tested for their ability to synthesize N-acyl-homoserine lactones (AHLs). AHL production was detected for four strains belonging to the lipoferum species and isolated from a rice rhizosphere. AHL molecules were structurally identified for two strains: Azospirillum lipoferum TVV3 produces 3O,C(8)-HSL (N-3-oxo-octanoyl-homoserine-lactone), C(8)-HSL (N-3-octanoyl-homoserine-lactone), 3O,C(10)-HSL (N-3-oxo-decanoyl-homoserine-lactone), 3OH,C(10)-HSL (N-3-hydroxy-decanoyl-homoserine-lactone) and C(10)-HSL (N-3-decanoyl-homoserine-lactone), whereas A. lipoferum B518 produced 3O,C(6)-HSL (N-3-oxo-hexanoyl-homoserine-lactone), C(6)-HSL (N-3-hexanoyl-homoserine-lactone), 3O,C(8)-HSL, 3OH,C(8)-HSL and C(8)-HSL. Genes involved in AHL production were characterized for A. lipoferum TVV3 by generating a genomic library and complementing an AHL-deficient strain with sensor capabilities. Those genes, designated alpI and alpR, were found to belong to the luxI and luxR families, respectively. When cloned in a suitable heterologous host, alpI and alpR could direct the synthesis of the five cognate AHLs present in A. lipoferum TVV3. These two adjacent genes were found to be located on a 85 kb plasmid. Southern hybridization experiments with probes alpI/R indicated that genes involved in AHL production in the three other AHL-producing strains were not closely related to alpI and alpR. This study demonstrates that AHL-based quorum-sensing is not widespread among the genus Azospirillum and could be found only in some A. lipoferum strains.
authors.affiliation: UMR-CNRS 5557 Ecologie Microbienne, Université Claude Bernard Lyon 1, Villeurbanne, France.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Vial
authors.forename: Caroline
authors.initials: C
authors.lastname: Cuny
authors.forename: Katia
authors.initials: K
authors.lastname: Gluchoff-Fiasson
authors.forename: Gilles
authors.initials: G
authors.lastname: Comte
authors.forename: Phil M
authors.initials: PM
authors.lastname: Oger
authors.forename: Denis
authors.initials: D
authors.lastname: Faure
authors.forename: Yves
authors.initials: Y
authors.lastname: Dessaux
authors.forename: René
authors.initials: R
authors.lastname: Bally
authors.forename: Florence
authors.initials: F
authors.lastname: Wisniewski-Dyé
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology; D016949:Azospirillum / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D026501:Blotting, Southwestern; D004269:DNA, Bacterial / Q000235:genetics; D017353:Gene Deletion; D015723:Gene Library; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D013058:Mass Spectrometry; D010944:Plants / Q000382:microbiology; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D053038:Quorum Sensing / Q000235:genetics / Q000502:physiology*; D012329:RNA, Bacterial / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D012329:RNA, Bacterial; C088386:homoserine lactone; D015107:4-Butyrolactone