Infections of Paramecium bursaria with bacteria and yeasts are reported. Bacteria and yeasts multiply in the algae-free ciliate and are transmitted at various conditions as are symbiotic chlorellae. Like chlorellae, the bacteria and the yeast cells are situated in perisymbiont vacuoles. Both bacteria and yeasts maintain their capability for independent existence and can be grown on standard nut...

a large input of energy and can occur either biologically, within the cells of various bacteria, or chemically, in fertilizer factories or during lightning storms. Among all living organisms, only bacteria have evolved the complex biochemical mechanisms required for nitrogen fixation. All "higher" plants and animals that are said to fix nitrogen are really only the symbiotic partners of the bac...