Figure 1. Transmission electron microscopy of Protochlamydia naegleriophila. A) Naegleria lovaniensis trophozoite after transfer of endocytobionts; strain KNic (p) from the original host strain showing 15 coccoid bacteria distributed randomly within the cytoplasm of the host ameba. N, nucleus; en, endosome (karyosome) within the nucleus; v, empty food vacuoles. Magnification ×10,500; bar = 1 μm. B) N. lovaniensis trophozoite jammed with numerous endoparasitic stages of Pr. naegleriophila. Magnification ×16,800; bar = 1 μm. C) Enlarged detail of N. lovaniensis trophozoite with intracytoplasmic stages of Pr. naegleriophila. Some stages show binary fission indicated by the fission furrow (arrows). The endoparasites have a wrinkled gram-negative outer membrane rendering a spiny appearance to the endoparasites. Signs of damage are obvious within the cytoplasm of the host ameba. mi, mitochondria. Magnification ×43,500; bar = 0.5 μm. D) Pr. naegleriophila within vacuoles of Acanthamoebae castellanii ameba 2 days postinfection. Elementary bodies (eb) and reticulate bodies (rb) are visible. Elementary bodies harbor a smooth membrane compared with the reticulate bodies, which have a spiny shape. Magnification ×10,000; bar = 2 μm. E) Enlarged detail of A. castellanii trophozoite with intracytoplasmic stages of Pr. naegleriophila 3 days postinfection. Binary fission is observed (di). Magnification ×20,000; bar = 1 μm. F) Crescent body (arrow) within A. castellanii observed 3 days postinfection. Magnification ×20,000; bar = 1 μm.