Caedibacter macronucleorum sp. nov., a Bacterium Inhabiting the Macronucleus of Paramecium duboscqui

The macronucleus of Paramecium duboscqui was observed to contain bacteria. Two morphologically different types of bacteria were found. Type 1 was 1.5-3.0 µm long and 0.5-0.8 µm wide. This type sometimes contained R bodies, which were associated with capsids of bacteriophages. The capability to producing R bodies was, however, lost in some host cell lines in laboratory culture. Type 2 had a length of 0.8 to 2.0 µm and a width of 0.4 µm, but sometimes occurred as much longer rods, which were straight, curved or crescent-shaped. Because of the morphological features of type 1 and of its ability to produce R bodies, the bacterium was named Caedibacter macronucleorum sp.n. Both types of bacteria were maintained by their host cells under all conditions tested. It cannot be decided, whether type 2 of the bacteria, which did not produce R bodies, represents a different stage or morph of the same species or belongs to a different species of bacteria. © 1993, Gustav Fischer Verlag Jena. All rights reserved.