Project description:Genome-wide transcription profiling of B. diazoefficiens (formerly B. japonicum) wild type and nnrR mutant strain which were grown in free-living anoxic denitrifying conditions (using nitrate as final electron aceptor). This study includes also the expression data of the wild type strain grown oxically (samples GSM210269 to GSM210283 in GEO record number GSE8478). Keywords: CRP/FNR proteins, in vitro transcription, microoxia, nitrogen oxides, Rhizobia, transcriptomics
Project description: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.
