title: [The discovery of naked cluster particles of Parachlamydia and its developmental mechanism].
abstract: OBJECTIVE
  To study the survival and developmental morphology of Parachlamydia (BN9) within Acanthamoeba.
  
  
  METHODS
  The morphology of BN9 within Acanthamoeba was studied by inverted phase contrast microscope, electron microscope, Gimenez and AO-staining with amoebal co-culture.
  
  
  RESULTS
  The endosomal maturation-blocked were formed after the egress of BN9. Two developmental stages-elementary and reticulate bodies, were both observed within the vacuoles. The reticulate bodies, multiplicated by binary fission, were located mainly within the vacuoles, while the elementary bodies can also be located in the plasma individually. The naked cluster particles were observed after the trophozoites cytolysis with Gimenez-staining. The light infectious trophozoites could encyst, and elementary bodies could survive within the mature cysts.
  
  
  CONCLUSIONS
  The egress of BN9 could form the endosomal maturation-blocked, which was presented in two developmental stages-elementary and reticulate bodies. It exhibited the cytolysin activity that could lyse the infectious trophozoites and were expelled in the vesicles. A few light infected amoeba could encyst with survival elementary bodies in the plasma.
authors.affiliation: School of Public Health, Fudan University, Shanghai 200032, China.
authors.forename: Qin-xue
authors.initials: QX
authors.lastname: Li
authors.forename: Qing-wu
authors.initials: QW
authors.lastname: Jiang
authors.forename: Jie
authors.initials: J
authors.lastname: Shen
authors.forename: Zi-hua
authors.initials: ZH
authors.lastname: Li
mesh_terms: D000048:Acanthamoeba / Q000382:microbiology* / Q000648:ultrastructure; D000818:Animals; D002695:Chlamydiales / Q000502:physiology / Q000648:ultrastructure*; D018920:Coculture Techniques; D006801:Humans; D002479:Inclusion Bodies / Q000648:ultrastructure*; D008018:Life Cycle Stages; D008854:Microscopy, Electron