An obligate intracellular bacterial pathogen forms a direct, interkingdom membrane contact site

June 06, 2023

Yamilex Acevedo-Sánchez (1), Patrick J. Woida (1), Stephan Kraemer (2), Rebecca L. Lamason (1)
bioRxiv. (6 June 2023). DOI:


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 Rickettsia parkeri 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 frequency of rickettsia-ER contacts, suggesting these interactions mimic organelle-ER contacts. Overall, our findings illuminate a direct, interkingdom membrane contact site uniquely mediated by rickettsia that seems to mimic traditional host MCSs.

How Our Software Was Used

Deep learning data segmentation was performed using Dragonfly to extract the organelles of interest. A U-Net model with five depth levels, a starting number of 64 convolutional kernels and a patch size of 64 pixels was then applied to the FIB-SEM image stack. 3D models were generated using the inferred data.

Author Affiliation

(1) Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
(2) Center for Nanoscale Systems, Harvard University, Cambridge, MA, USA