Open AccessPathogen–host reorganization during C hlamydia invasion revealed by cryo‐electron tomography
Author(s) -
Nans Andrea,
Saibil Helen R.,
Hayward Richard D.
Publication year - 2014
Publication title -
cellular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.542
H-Index - 138
eISSN - 1462-5822
pISSN - 1462-5814
DOI - 10.1111/cmi.12310
Subject(s) - chlamydiae , biology , microbiology and biotechnology , obligate , chlamydia trachomatis , endosome , ornithosis , pathogen , intracellular , virology , ecology
Summary Invasion of host cells is a key early event during bacterial infection, but the underlying pathogen–host interactions are yet to be fully visualized in three‐dimensional detail. We have captured snapshots of the early stages of bacterial‐mediated endocytosis in situ by exploiting the small size of chlamydial elementary bodies ( EBs ) for whole‐cell cryo‐electron tomography. C hlamydiae are obligate intracellular bacteria that infect eukaryotic cells and cause sexually transmitted infections and trachoma, the leading cause of preventable blindness. We demonstrate that C hlamydia trachomatis LGV 2 EBs are intrinsically polarized. One pole is characterized by a tubular inner membrane invagination, while the other exhibits asymmetric periplasmic expansion to accommodate an array of type III secretion systems ( T 3 SSs ). Strikingly, EBs orient with their T 3 SS ‐containing pole facing target cells, enabling the T 3 SSs to directly contact the cellular plasma membrane. This contact induces enveloping macropinosomes, actin‐rich filopodia and phagocytic cups to zipper tightly around the internalizing bacteria. Once encapsulated into tight early vacuoles, EB polarity and the T 3 SSs are lost. Our findings reveal previously undescribed structural transitions in both pathogen and host during the initial steps of chlamydial invasion.