title: Structural properties of the tubular appendage spinae from marine bacterium Roseobacter sp. strain YSCB.
abstract: Spinae are tubular surface appendages broadly found in Gram-negative bacteria. Little is known about their architecture, function or origin. Here, we report structural characterization of the spinae from marine bacteria Roseobacter sp. YSCB. Electron cryo-tomography revealed that a single filament winds into a hollow flared base with progressive change to a cylinder. Proteinase K unwound the spinae into proteolysis-resistant filaments. Thermal treatment ripped the spinae into ribbons that were melted with prolonged heating. Circular dichroism spectroscopy revealed a dominant beta-structure of the spinae. Differential scanning calorimetry analyses showed three endothermic transformations at 50-85°C, 98°C and 123°C, respectively. The heating almost completely disintegrated the spinae, abolished the 98°C transition and destroyed the beta-structure. Infrared spectroscopy identified the amide I spectrum maximum at a position similar to that of amyloid fibrils. Therefore, the spinae distinguish from other bacterial appendages, e.g. flagella and stalks, in both the structure and mechanism of assembly.
authors.affiliation: Service de Microscopie Electronique, Institut de Microbiologie de la Méditerranée, Aix-Marseille University , CNRS, 31 chemin Joseph Aiguier, 13402 Marseille cedex 20, France.
authors.forename: A
authors.initials: A
authors.lastname: Bernadac
authors.forename: L-F
authors.initials: LF
authors.lastname: Wu
authors.forename: C-L
authors.initials: CL
authors.lastname: Santini
authors.forename: C
authors.initials: C
authors.lastname: Vidaud
authors.forename: J N
authors.initials: JN
authors.lastname: Sturgis
authors.forename: N
authors.initials: N
authors.lastname: Menguy
authors.forename: P
authors.initials: P
authors.lastname: Bergam
authors.forename: C
authors.initials: C
authors.lastname: Nicoletti
authors.forename: T
authors.initials: T
authors.lastname: Xiao
mesh_terms: D002152:Calorimetry, Differential Scanning; D022081:Cell Surface Extensions / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D002942:Circular Dichroism; D020285:Cryoelectron Microscopy; D041904:Roseobacter / Q000378:metabolism*; D013696:Temperature