Saccamoeba sp. harbouring both Mimivirus-like polyhedral virions and cuboidal intravacuolar bacteria

strain at‐tracted our attention because some of the trophozoites ap‐peared to harbour an unusual endocytobiont. Both the obvi‐ously infected and the uninfected trophozoites were isolated separately on fresh agar plates. Cultures of the infected saccamoebae which appeared to be prone to death and de‐cay were suspended in amoeba saline according to Page (1988) and the suspension passed through a Millipore filter with a pore size of 5.0 µm. 100 µl of this suspension was co‐cultivated with uninfected trophozoites to obtain sufficient material for electron microscopical investigation. The cul‐tures were studied by phase‐contrast light microscopy using a Leica Laborlux device. On the 5th day after reinfection the parasitized saccamoebae were harvested from several NN‐agar plates and then concentrated to a pellet by centrifugation at 1800 rpm for 15 min. The pellet was immediately fixed with 3% ice‐cold glutaraldehyde in 0.1 M cacodylate buffer (pH 7.2). After pre‐fixation the specimens were fixed in 1% osmium tetroxide and then in 2% uranyl acetate in aqueous solution. Subsequently, specimens were dehydrated in alcohol and embedded in Spurr's epoxy resin. Thin sections were stained with 1% lead citrate and examined using a Zeiss EM 910 electron microscope.