One Face of Chlamydia trachomatis: The Infectious Elementary Body
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The lifestyle of Chlamydiae is unique: the bacteria alternate between two morphologically distinct forms, an infectious non-replicative elementary body (EB), and a replicative, non-infectious reticulate body (RB). This review focuses on recent advances in understanding the structure and function of the infectious form of the best-studied member of the phylum, the human pathogen Chlamydia trachomatis. Once considered as an inert particle of little functional capacity, the EB is now perceived as a sophisticated entity that encounters at least three different environments during each infectious cycle. We review current knowledge on its composition and morphology, and emerging metabolic activities. These features confer resistance to the extracellular environment, the ability to penetrate a host cell and ultimately enable the EB to establish a niche enabling bacterial survival and growth. The bacterial and host molecules involved in these processes are beginning to emerge.
We thank Dr. Andrea Nans for providing the EM image shown in Fig. 1. This work was supported by the European Research Council (NUChLEAR grant number 282046), the Agence Nationale pour la Recherche (Expendo ANR-14-CE11-0024-02), the Institut Pasteur and the Centre National de la Recherche Scientifique. Research on EB structure and inclusion biogenesis is supported by projects grants MR/N000846/1 and MR/I008696/1 from the Medical Research Council to R.D.H.
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