Abstract
The division of mitochnodrial nuclei in Amoeba proteus, Paramecium caudatum, Nitella flexilis and Allium cepa was investigated using 4'-6-diamidino-2-phenylindole (DAPI) epifluorescent microscopy. The mitochondria each contained one mt-nucleus in Amoeba proteus and Paramecium caudatum and one or two mt-nuclei in Nitella flexilis and Allium cepa. The ratio of fluorescent intensity (grain density of negative film) among one DNA molecule of a T4 phage particle and mt-nuclei of spherical mitochondria in Physarum polycepaalum, Amoeba proteus, Paramecium caudatum, Nitella flexilis and Allium cepa was about 1:16:22:5:0.4:0.4. That is, the mitochondrial DNA content in Nitella flexilis and Allium cepa was much smaller than those in Amoeba proteus and Paramecium caudatum. The mitochondria and their nuclei in Amoeba proteus and Paramecium caudatum as well as Physarum polycephalum divided simultaneously by constriction, while segregation of mitochondria) nuclei occurred before the mitochondrial division in Nitella flexilis and Allium cepa. The fluorescent intensity of mt-nuclei in dumbbell-shaped mitochondria of Paramecium caudatum and Allium cepa was about twice that in spherical mitochondria. Therefore, mitochondrial DNA probably duplicated and divided equally into daughter mitochondria.
