Studies On Chlamydia Trachomatis And Its T3SS Structures By Electron Microscopy

Chlamydia is a type of gram-negative bacteria lived strictly in cells and widely infects birds,humans and other mammals.Among them,Chlamydia trachomatis can cause trachoma that can result in infectious blindness,and genitourinary tract infections that can lead to great harm to human health.The Type III secretion system(T3SS)plays important roles in the process of pathogenic bacteria infecting host cells.In this paper,the oviduct of patients infected with Chlamydia trachomatis,the in vitro cultured Chlamydia trachomatis and its invading host cells were observed through transmission electron microscope(TEM),after preparation by conventional EM sample preparation methods and high pressure rapid freezing-freeze substitution(HPF/FS),respectively.In order to further understand the mechanism of Chlamydia trachomatis invasion of host cells,Cryo-Electron Tomography(Cryo-ET)and ET-average were applied to the Chlamydia trachomatis and its invading cells.The results are listed as follows:1.The oviduct secretory cells of patients infected with Chlamydia trachomatis were vacuolated.Even more,the structure of some tissues was seriously destroyed.Chlamydia-like structures were observed in the clinical samples.2.Better structures of cultured Chlamydia trachomatis and host cell,were observed by applying high-pressure rapid freezing together with the freezesubstitution,and T3 SSs were observed on Chlamydia trachomatis inside the host cells.3.The in situ three-dimensional structures of Chlamydia trachomatis in different status were unveiled,and the process of Chlamydia invasion of host cells was captured in situ,.4.The in situ three-dimensional structures of the T3 SSs of Chlamydia trachomatis in free and in contact with host cells were obtained.