Abstract
Chlamydiales order members are obligate intracellular bacteria, dividing by binary fission. However, Chlamydiales lack the otherwise conserved homologue of the bacterial division organizer FtsZ and certain division protein homologues. FtsZ might be functionally replaced in Chlamydiales by the actin homologue MreB. RodZ, the membrane anchor of MreB, localizes early at the division septum. In order to better characterize the organization of the chlamydial divisome, we performed co-immunoprecipitations and yeast-two hybrid assays to study the interactome of RodZ, using Waddlia chondrophila, a potentially pathogenic Chlamydia-related bacterium, as a model organism. Three potential interactors were further investigated: SecA, FtsH, and SufD. The gene and protein expression profiles of these three genes were measured and are comparable with recently described division proteins. Moreover, SecA, FtsH, and SufD all showed a peripheral localization, consistent with putative inner membrane localization and interaction with RodZ. Notably, heterologous overexpression of the abovementioned proteins could not complement E. coli mutants, indicating that these proteins might play different functions in these two bacteria or that important regulators are not conserved. Altogether, this study brings new insights to the composition of the chlamydial divisome and points to links between protein secretion, degradation, iron homeostasis, and chlamydial division.
Highlights
Chlamydiales are Gram-negative, obligate intracellular bacteria sharing a unique biphasic developmental cycle
Chlamydial division has been a mystery for a long time due to its minimal division machinery, which lacks several division proteins that are essential in other bacteria
In order to investigate the composition of the chlamydial divisome more in depth, we took advantage of a recent characterization of proteins binding to W. chondrophila PG performed in our laboratory [37]
Summary
Chlamydiales are Gram-negative, obligate intracellular bacteria sharing a unique biphasic developmental cycle. Chlamydial division has been a mystery for a long time due to its minimal division machinery, which lacks several division proteins that are essential in other bacteria. This reduced division machinery is conserved among members of the Chlamydiales order, both in the well-described Chlamydiaceae family and as in Chlamydia-related bacteria [1]. The Chlamydiaceae family includes several well-known human pathogens, such as Chlamydia trachomatis, Chlamydia pneumoniae, and Chlamydia psittaci. C. pneumoniae and C. psittaci infections can lead to respiratory tract infections in humans, such as pneumonia [4], bronchitis [5], and psittacosis, respectively [6]. W. chondrophila DNA was detected in nasopharyngeal samples from children with bronchitis [12] and in respiratory samples from patients with pneumonia [13]
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