biostudies-literatureUnknownAcevedo-Sanchez YNIAID NIH HHSNIGMS NIH HHSInterorganelle communication regulates cellular homeostasis through the formation of tightly-associated membrane contact sites ^1-3. Prior work has identified several ways that intracellular pathogens alter contacts between eukaryotic membranes ^4-6, but there is no existing evidence for contact sites spanning eukaryotic and prokaryotic membranes. Here, using a combination of live-cell microscopy and transmission and focused-ion-beam scanning electron microscopy, we demonstrate that the intracellular bacterial pathogen <i>Rickettsia parkeri</i> forms a direct membrane contact site between its bacterial outer membrane and the rough endoplasmic reticulum (ER), with tethers that are approximately 55 nm apart. Depletion of the ER-specific tethers VAPA and VAPB reduced the fbioRxiv : the preprint server for biology2023.06.05.543771https://www.ebi.ac.uk/biostudies/studies/S-EPMC10274737biostudies-literatureAn obligate intracellular bacterial pathogen forms a direct, interkingdom membrane contact site.PMC10274737R01 AI155489R01 GM141025T32 GM007287Acevedo-Sanchez YLamason RLWoida PJKraemer SfalseAn obligate intracellular bacterial pathogen forms a direct, interkingdom membrane contact site.Interorganelle communication regulates cellular homeostasis through the formation of tightly-associated membrane contact sites ^1-3. Prior work has identified several ways that intracellular pathogens alter contacts between eukaryotic membranes ^4-6, but there is no existing evidence for contact sites spanning eukaryotic and prokaryotic membranes. Here, using a combination of live-cell microscopy and transmission and focused-ion-beam scanning electron microscopy, we demonstrate that the intracellular bacterial pathogen <i>Rickettsia parkeri</i> forms a direct membrane contact site between its bacterial outer membrane and the rough endoplasmic reticulum (ER), with tethers that are approximately 55 nm apart. Depletion of the ER-specific tethers VAPA and VAPB reduced the f2023-01-01T00:00:00Z2023 Jun2026-06-22T03:17:31.684Z2025-04-06T12:23:14.3ZS-EPMC102747373733313310.1101/2023.06.05.543771