A Ubiquitous Platform for Bacterial Nanotube Biogenesis

Abstract

Summary: We have previously described the existence of membranous nanotubes, bridging adjacent bacteria, facilitating intercellular trafficking of nutrients, cytoplasmic proteins, and even plasmids, yet components enabling their biogenesis remain elusive. Here we reveal the identity of a molecular apparatus providing a platform for nanotube biogenesis. Using Bacillus subtilis (Bs), we demonstrate that conserved components of the flagellar export apparatus (FliO, FliP, FliQ, FliR, FlhB, and FlhA), designated CORE, dually serve for flagellum and nanotube assembly. Mutants lacking CORE genes, but not other flagellar components, are deficient in both nanotube production and the associated intercellular molecular trafficking. In accord, CORE components are located at sites of nanotube emergence. Deleting COREs of distinct species established that CORE-mediated nanotube formation is widespread. Furthermore, exogenous COREs from diverse species could restore nanotube generation and functionality in Bs lacking endogenous CORE. Our results demonstrate that the CORE-derived nanotube is a ubiquitous organelle that facilitates intercellular molecular trade across the bacterial kingdom. : Bhattacharya et al. show that bacterial intercellular nanotubes, facilitating cytoplasmic molecular exchange among cells, emerge from conserved CORE components of the flagellar export apparatus. CORE-mediated nanotube formation is widespread among bacterial species. The results establish the CORE-derived nanotube as a ubiquitous organelle, facilitating intercellular molecular trafficking across the bacterial kingdom. Keywords: Bacillus subtilis, nanotubes, flagellar export apparatus, flagella type III secretion system, bacterial communication, contact-dependent molecular exchange, bacterial community