Case 125. 

Electron micrograph of cultured Acanthamoeba castellanii
　 　 　 　
　 Ultrastructurally, targeted round nucleus with central karyosome and vacuolated cytoplasm are noted. The ameba contains electron-dense mitochondria. 　
　 　 　 　

　

 　 Acanthamoeba sp. and Naegleria sp. belong to free-living ameba seen widespread in the environmental warm water, so that they are aerobic, contain mitochondria, and lack glycogen particles. In contrast, Entamoeba sp. is oblilgately anerobic, lack mitochondria, and are rich in glycogen.