Abstract
Intracytoplasmic presence of bacterial endosymbionts within an isolate of Acanthamoeba from cooling tower water (KA/W4), was confirmed by transmission electron microscopy. The isolate was closely related with the L3a strain of A. lugduensis based on ribosomal RNA gene 9rDNA) PCR-restriction fragment length polymorphism (RFLP), mitochondrial (mt) DNA REFL and multilocus enzyme electrophoresis (MLEE) analyses. The endosymbionts were randomly distributed in both trophozites and cysts, and were gram negative, rod-shaped bacteria measuring approximately 1.3 x 0.39 micro-m. They were neither included in lacunae-like structure nor surrounded by phagosomal or phagolysosomal membranes.