A 3D Soft X-Ray Structural Atlas of Multicellular Cable Bacteria

SUMMARY The multicellular filamentous cable bacteria perform centimeter-scale electron transport via a continuous periplasmic conductive network. Resolving how this electrical architecture is coordinated with intracellular organization requires an integrated approach coupling 3D ultrastructure with in situ biochemical composition. Here, we integrate soft X-ray tomography (SXT) with cryo-electron tomography, elemental mapping, and fluorescence microscopy to generate a volumetric 3D atlas of intact cable bacteria filaments. Whole-cell reconstructions reveal physiological heterogeneity and cell-cycle-dependent reorganization of intracellular vesicles and granules. X-ray absorption measurements resolve biochemical differences within the physically continuous conductive apparatus, where periplasmic conductive fibers possess higher biomolecular density than junction lamellae at cell junctions. Furthermore, cell elongation preceding division is associated with two high-density, ring-like nucleoid-associated domains, accompanied by asymmetric membrane constriction and localized FtsZ assemblies. These findings establish SXT as a powerful approach for studying multicellular bacterial organization and provide a multi-scale framework for understanding the conductive machinery of cable bacteria.