Saccamoeba sp. isolated from the bark of a sycamore tree harboured polyhedral particles of 430 - 450 nm in diameter. These particles consisted of capsids surrounded by a ring of 140 nm-long fibrils - all features resembling Mimivirus. In addition, a large virus factory was found. The presence of early, intermediate, and final morphogenesis stages allows the study of various stages of virion development. Application of filtered suspensions from decaying saccamoebae resulted in infection of healthy saccamoebae. Another endocytobiont of bacterial nature was observed within a few Saccamoeba trophozoites as well. These bacteria were 400-500 nm long and had a cuboidal shape.