Membrane remodelling is fundamental to cellular life, essential for processes ranging from cell division to organelle maintenance. While lipid bilayers are the predominant membrane structure, non-bilayer lipids and phases play crucial roles in cellular function and stress responses. Proteins are key mediators of membrane remodelling, with the dynamin superfamily representing an ancient and conserved class of membrane remodelling GTPases found across all domains of life. Most eukaryotic dynamins and dynamin-related proteins have defined roles in fission or fusion, such as the mitofusins mediating outer mitochondrial membrane fusion. Bacterial dynamins generally have more diverse cellular roles, but often share conserved characteristics with eukaryotic dynamins, including their domain architecture and ability to self-assemble into helical polymers that constrict lipid membranes. Bacterial dynamin-like protein (BDLP) from the cyanobacterium Nostoc punctiforme serves as a valuable model for investigating bacterial dynamin function and the fundamental membrane remodelling principles of the dynamin superfamily, especially given its homology to the mitofusins. This thesis demonstrates BDLP's specific upregulation during development of motile N. punctiforme filaments, and its putative association with thylakoid membranes remodelled into non-bilayer phases. High-resolution cryo-electron microscopy structures of GMPPNP- and GDP-bound BDLP filaments provide a structural basis of GTP coordination and
catalysis, and demonstrate a novel mechanism of membrane constriction. Cryo-electron tomography reveals how BDLP remodels lipids from a bilayer configuration into a non-bilayer arrangement in vitro, providing the first evidence of a dynamin family member mediating stable lipid phase transitions. These findings expand our understanding of bacterial DRP functions while demonstrating conserved DSF membrane remodelling principles. The identification of a conserved membrane displacement domain across mitofusin-like DRPs suggests a shared mechanism for bilayer disruption, potentially elucidating mitofusin-mediated fusion.