Structure of the Mate-Killer (mu) particles in Paramecium aurelia, stock 540

Abstract

SUMMARYThe mate-killer (mu) particles in the cytoplasm of Paramecium aurelia, stock 540, variety (syngen) 1, were studied by : Feulgen-staining ; phase-contrast microscopy ; fluorescence under ultraviolet irradiation after staining with acridine orange ; electron microscopy (including the ' silver-Feulgen ' technique). The appearance of the particles following treatment with DNAase and RNAase was observed. It was found that the mu particles were capsulated rod-shaped structures, 2-lop long and about 0 . 3 ,~ in diameter (excluding the capsule); they appeared to reproduce by transverse fission without formation of cross-walls. There was an external double membrane and the internal material consisted largely of DNA, which was not limited to particular zones but spread throughout the interior of the particle. RNA was also present, The relationships of the particles to other micro-organisms is discussed, and it is concluded that they do not differ from bacteria in any important respect.

Bacterial Endosymbiosis in Paramecium aurelia: Bacteriophage-like Inclusions in a Kappa Symbiont

“…A number of endosymbionts of Paramecium aiirelia occur in vesicles (Beale et al 1969;Stevenson, 1970)~ but kappa symbionts normally do not. Vesicles of various types, some of which have digestive function, are common in the cytoplasm of P. aurelia (Jurand & Selman, 1969), SO symbionts might be digested in this way.…”

“…Cell numbers were counted by removing cells one by one from a sample of culture; symbiont numbers were counted by taking representative fields of random cells prepared by the Os0,-lactoorcein method (Beale & Jurand, 1966) and counting symbionts with the aid of a squared grid in the ocular. Symbionts bearing R bodies ('large') may be distinguished from those not having R bodies small') by their different size (particularly breadth) and the fact that large forms stain more intensely.…”

Studies on the RNA of the mate-killer particles of paramecium

“…Light microscopy revealed that they had the size and shape of bacteria, and they occurred in numbers from 100 to 1000 per cell, depending on the type of particle. Studies with the electron microscope showed that they consist of a double membrane and granular internal contents (Jurand and Preer, 1968;Beale and Jurand, 1960). These granules were approximately the size of ribosomes (Jurand and Preer, 1968).…”

“…These macromolecules have been reported to be present in situ, using cytochemical techniques (Beale and Jurand, 1960). Also, specific enzymes have been shown to be present in isolated particles, e.g.…”

Ultrastructure of Flagellated Lambda Symbionts in Paramecium aurelia

“…To observe the symbionts in situ two methods were used. In the first, whole paramecia were observed with a dark phase-contrast microscope (Carl Zeiss), using paramecia treated with lactoorcein according to the method of Beale & Jurand (1966). In the second, I p Araldite sections were mounted on slides, stained with toluidine blue and observed with ordinary bright-field microscopy.…”