Entamoeba histolytica: DNA carrier vesicles in nuclei and kinetoplast-like organelles (EhkOs)

Abstract.

Entamoeba histolytica, the protozoan responsible for human amoebiasis, has a complex genome, whose linear chromosomes and DNA circles have so far eluded detailed analysis. We report the detection by transmission electron microscopy of nuclear vesicles (0.05–0.3 µm in diameter) carrying DNA in E. histolytica trophozoites. In late anaphase many of these nuclear vesicles were found to be organized in structures of ∼2.5×1 µm, in association with chromosomes and microtubules. In glutaraldehyde-fixed and detergent-treated trophozoites, nuclear vesicles displayed a non-membranous envelope. Binding of phosphotungstate stain and recognition by serum from patients with systemic lupus erythematosus indicated that these vesicles contain DNA. Similar DNA carrier vesicles were found in the cytoplasm and in the E. histolytica kinetoplast-like organelle (EhkO). By Feulgen staining, we detected DNA carrier vesicles entering or leaving the nuclei, suggesting a structural relationship between the nuclear vesicles and the vesicles present in the EhkOs.