Division without Binary Fission: Cell Division in the FtsZ-Less Chlamydia

Abstract

Chlamydia is an obligate intracellular bacterial pathogen that has significantly reduced its genome size in adapting to its intracellular niche. Among the genes that Chlamydia has eliminated is ftsZ, encoding the central organizer of cell division that directs cell wall synthesis in the division septum. These Gram-negative pathogens have cell envelopes that lack peptidoglycan (PG), yet they use PG for cell division purposes. Recent research into chlamydial PG synthesis, components of the chlamydial divisome, and the mechanism of chlamydial division have significantly advanced our understanding of these processes in a unique and important pathogen. For example, it has been definitively confirmed that chlamydiae synthesize a canonical PG structure during cell division. Various studies have suggested and provided evidence that Chlamydia uses MreB to substitute for FtsZ in organizing and coordinating the divisome during division, components of which have been identified and characterized. Finally, as opposed to using an FtsZ-dependent binary fission process, Chlamydia employs an MreB-dependent polarized budding process to divide. A brief historical context for these key advances is presented along with a discussion of the current state of knowledge of chlamydial cell division.

Keywords: Chlamydia; FtsZ; MreB; binary fission; cell division; penicillin; peptidoglycan; polarized budding.

FIG 1

(A) Structured illumination microscopy image of 10.5-h postinfection C. trachomatis expressing MreB-6×H. Major outer membrane protein (MOMP) (red), Hsp60 (purple), and chlamydial MreB (green) are shown. Scale bar = 0.5 μm. The boxed region is illustrated in panel B. (B) Schematic illustrating the known and putative chlamydial inner membrane divisome components. Known interactions are shown with a yellow star, whereas putative interactions based on orthologous systems are shown with a gray star.