The cellular ceramide transport protein CERT promotes Chlamydia psittaci infection and controls bacterial sphingolipid uptake.

Chlamydiaceae are bacterial pathogens that cause diverse diseases in humans and animals. Despite their broad host and tissue tropism, all Chlamydia species share an obligate intracellular cycle of development and have evolved sophisticated mechanisms to interact with their eukaryotic host cells. Here, we have analysed interactions of the zoonotic pathogen Chlamydia psittaci with a human epithelial cell line. We found that C. psittaci recruits the ceramide transport protein (CERT) to its inclusion. Chemical inhibition and CRISPR/Cas9-mediated knockout of CERT showed that CERT is a crucial factor for C. psittaci infections thereby affecting different stages of the infection including inclusion growth and infectious progeny formation. Interestingly, the uptake of fluorescently labelled sphingolipids in bacteria inside the inclusion was accelerated in CERT-knockout cells indicating that C. psittaci can exploit CERT-independent sphingolipid uptake pathways. Moreover, the CERT-specific inhibitor HPA-12 strongly diminished sphingolipid transport to inclusions of infected CERT-knockout cells, suggesting that other HPA-12-sensitive factors are involved in sphingolipid trafficking to C. psittaci. Further analysis is required to decipher these interactions and to understand their contributions to bacterial development, host range, tissue tropism, and disease outcome.