Case 125. 

Electron micrograph of cultured Acanthamoeba castellanii
　 　 　 　
　 At the periphery of the cytoplasm just beneath the plasma membrane, bundles of fine filaments are seen. μm 　
　 　 　 　

　

 　 Acanthamoeba sp. and Naegleria sp. are a reservoir of Legionella pneumophila in water. L. pneumophila belongs to be an obligate intracellular microbe. Both ameba species, particularly Naegleria sp., preferentially grows at 42℃, the temperature of hot springs. Hot spiring bathing is thus a risk factor of legionnaire's disease.