Kingdoms of bacteria and cell organelles collide as bacteria and cells form captivating connections inside cells

Amazing stuff!

"... New research ... has shown that Rickettsia parkeri, a bacterial pathogen that lives freely in the cytosol, can interact in an extensive and stable way with the rough endoplasmic reticulum, forming previously unseen contacts with the organelle.

It’s the first known example of a direct interkingdom contact site between an intracellular bacterial pathogen and a eukaryotic membrane. ...

Rickettsia is difficult to study because it is an obligate pathogen, meaning it can only live and reproduce inside living cells, much like a virus. Researchers must get creative to parse out fundamental questions and molecular players in the R. parkeri life cycle, and much remains unclear about how R. parkeri spreads. ...

an unexpectedly high percentage of R. parkeri surrounded and enveloped by the ER, at a distance of about 55 nanometers. This distance is significant because membrane contacts for interorganelle communication in eukaryotic cells form connections from 10-80 nanometers wide. The researchers ruled out that what they saw was not an immune response, and the sections of the ER interacting with the R. parkeri were still connected to the wider network of the ER. ..."

From the abstract:

"Upon invasion into the host cell, a subset of bacterial pathogens resides exclusively in the cytosol. While previous research revealed how they reshape the plasma membrane during invasion, subvert the immune response, and hijack cytoskeletal dynamics to promote their motility, it was unclear if these pathogens also interacted with the organelles in this crowded intracellular space.

Here, we examined if the obligate intracellular pathogen Rickettsia parkeri interacts with the endoplasmic reticulum (ER), a large and dynamic organelle spread throughout the cell.

Using live-cell microscopy and transmission and focused-ion-beam scanning electron microscopy, we show that R. parkeri forms extensive contacts with the rough ER that are ∼55 nm apart and cover more than half the bacterial surface. Depletion of the ER-specific tethers VAPA and VAPB reduced rickettsia–ER contacts, and VAPA and VAPB were localized around intracellular rickettsiae. Overall, our findings illuminate an interkingdom ER contact uniquely mediated by rickettsiae that mimics some characteristics of traditional host membrane contact sites."

Kingdoms collide as bacteria and cells form captivating connections | MIT News | Massachusetts Institute of Technology "Studying the pathogen R. parkeri, researchers discovered the first evidence of extensive and stable interkingdom contacts between a pathogen and a eukaryotic organelle."

Rickettsia parkeri forms extensive, stable contacts with the rough endoplasmic reticulum (no public access)

The bacterium R. parkeri (magenta) can be seen here forming direct interkingdom contacts with the rough endoplasmic reticulum (cyan), the first known example of an intracellular pathogen interacting with a eukaryotic membrane in this way.