Abstract
Chlamydiae, such as Chlamydia trachomatis and Chlamydia pneumoniae, can cause chronic infections. It is believed that persistent forms called aberrant bodies (ABs) might be involved in this process. AB formation seems to be a common trait of all members of the Chlamydiales order and is caused by distinct stress stimuli, such as β-lactam antibiotics or nutrient starvation. While the diverse stimuli inducing ABs are well described, no comprehensive morphological characterization has been performed in Chlamydiales up to now. We thus infected mammalian cells with the Chlamydia-related bacterium Waddlia chondrophila and induced AB formation using different stimuli. Their morphology, differences in DNA content and in gene expression were assessed by immunofluorescence, quantitative PCR, and reverse transcription PCR, respectively. All stimuli induced AB formation. Interestingly, we show here for the first time that the DNA gyrase inhibitor novobiocin also caused appearance of ABs. Two distinct patterns of ABs could be defined, according to their morphology and number: (i) small and multiple ABs versus (ii) large and rare ABs. DNA replication of W. chondrophila was generally not affected by the different treatments. Finally, no correlation could be observed between specific types of ABs and expression patterns of mreB and rodZ genes.
Highlights
The Chlamydiales order is composed of obligate intracellular Gram-negative bacteria, which are classified either in the Chlamydiaceae family or in several other family-level lineages commonly referred to as “Chlamydia-related bacteria”
elementary bodies (EBs) reside in a vacuole referred to as an inclusion and are converted into noninfectious dividing reticulate bodies (RBs) [14], which replicate by binary fission
Vero cells were selected as host cells, since they are better suited for drug susceptibility tests than amoebae, which harbor efflux machineries that protect them from chemical compounds [36]
Summary
The Chlamydiales order is composed of obligate intracellular Gram-negative bacteria, which are classified either in the Chlamydiaceae family or in several other family-level lineages commonly referred to as “Chlamydia-related bacteria”. Belonging to the Waddliaceae family, Waddlia chondrophila, a Chlamydia-related bacterium, is considered as a potential agent of abortion in ruminants [2,3,4] and of adverse pregnancy outcomes in humans [5,6,7,8]. W. chondrophila DNA was detected in nasopharyngeal aspirates from children with bronchiolitis [10] and in respiratory samples from patients with pneumonia [11], suggesting a potential role of this bacterium in respiratory diseases. EBs reside in a vacuole referred to as an inclusion and are converted into noninfectious dividing reticulate bodies (RBs) [14], which replicate by binary fission. RBs redifferentiate into EBs, which are released by exocytosis or by cell lysis, allowing the initiation of a new life cycle [13,15]
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