ジャーナル: PLoS Biol / 年: 2025 タイトル: Mapping the ultrastructural topology of the corynebacterial cell surface. 著者: Buse Isbilir / Anna Yeates / Vikram Alva / Tanmay A M Bharat / 要旨: Corynebacterium glutamicum is a diderm bacterium extensively used in the industrial-scale production of amino acids. Corynebacteria belong to the bacterial family Mycobacteriaceae, which is ...Corynebacterium glutamicum is a diderm bacterium extensively used in the industrial-scale production of amino acids. Corynebacteria belong to the bacterial family Mycobacteriaceae, which is characterized by a highly unusual cell envelope with an outer membrane consisting of mycolic acids, called mycomembrane. The mycomembrane is further coated by a surface (S-)layer array in C. glutamicum, making this cell envelope highly distinctive. Despite the biotechnological significance of C. glutamicum and biomedical significance of mycomembrane-containing pathogens, ultrastructural and molecular details of its distinctive cell envelope remain poorly characterized. To address this, we investigated the cell envelope of C. glutamicum using electron cryotomography and cryomicroscopy of focused ion beam-milled single and dividing cells. Our cellular imaging allowed us to map the different components of the cell envelope onto the tomographic density. Our data reveal that C. glutamicum has a variable cell envelope, with the S-layer decorating the mycomembrane in a patchy manner. We further isolated and resolved the structure of the S-layer at 3.1 Å-resolution using single particle electron cryomicroscopy. Our structure shows that the S-layer of C. glutamicum is composed of a hexagonal array of the PS2 protein, which interacts directly with the mycomembrane via an anchoring segment containing a coiled-coil motif. Bioinformatic analyses revealed that the PS2 S-layer is sparsely yet exclusively present within the Corynebacterium genus and absent in other genera of the Mycobacteriaceae family, suggesting distinct evolutionary pathways in the development of their cell envelopes. Our structural and cellular data collectively provide a topography of the unusual C. glutamicum cell surface, features of which are shared by many pathogenic and microbiome-associated bacteria, as well as by several industrially significant bacterial species.
凍結剤: ETHANE / チャンバー内湿度: 95 % / チャンバー内温度: 283 K / 装置: FEI VITROBOT MARK IV 詳細: 3.5 microlitre of cell suspension was apllied to Quantifoil R1 4 SiO2 Au 200 mesh grids and plunge frozen into liquid ethane using a Vitrobot Mark IV after wait time of 3 minutes with -7 blot ...詳細: 3.5 microlitre of cell suspension was apllied to Quantifoil R1 4 SiO2 Au 200 mesh grids and plunge frozen into liquid ethane using a Vitrobot Mark IV after wait time of 3 minutes with -7 blot force and 13 seconds of blot time..
Cryo protectant
2.5% glycerol
切片作成
集束イオンビーム - 装置: OTHER / 集束イオンビーム - イオン: OTHER / 集束イオンビーム - 電圧: 30 / 集束イオンビーム - 電流: 0.1 / 集束イオンビーム - 時間: 1800 / 集束イオンビーム - 温度: 93 K / 集束イオンビーム - Initial thickness: 700 / 集束イオンビーム - 最終 厚さ: 150 集束イオンビーム - 詳細: After loading the frozen specimen into the microscope, the grids were sputter coated with metallic platinum (0.1 mbar; 30 mA, 1V, 30 seconds), then mapped using the ...集束イオンビーム - 詳細: After loading the frozen specimen into the microscope, the grids were sputter coated with metallic platinum (0.1 mbar; 30 mA, 1V, 30 seconds), then mapped using the MAPs software (v. 3.27; ThermoFisher Inc). A coating of organic platinum was then applied via gas injection system following previous reports (Lam & Villa, 2021) for 20 seconds, followed by a final sputter-coat, using the same settings as previously. AutoTEM (v. 2.4.3; ThermoFisher Inc) was set to rough mill the lamellae in three steps with currents of 0.5 nA, 0.3 nA and 0.1 nA and with milling angle of 10 degree. Lamellae polishing was performed at 50 pA and then finally at 30 pA current with a 0.5 degree overtilt to produce lamellae with a final 100-200 nm thickness.. The value given for _em_focused_ion_beam.instrument is TFS Aquilos 2 DualBeam FIB-SEM. This is not in a list of allowed values {'OTHER', 'DB235'} so OTHER is written into the XML file.