FURTHER INVESTIGATIONS ON PRE-LETHAL EFFECTS OF KILLING ACTION OF KAPPA CONTAINING KILLER STOCKS OF PARAMECIUM-AURELIA

Kappa symbionts of two stocks of Paramecium aurelia were isolated and their killing activity tested on sensitive paramecia. The symbionts from stock 51, which is a hump killer, induce sensitive animals to cease the formation of food vacuoles due to changes at the bottom of the buccal cavity in the food vacuole forming area (the naked ribbed wall). Instead of normal food vacuoles only narrow elongated outpocketings are formed. Food vacuoles which have been formed during treatment contain kappa symbionts. After disintegration due to digestion of the symbiont cells the R bodies unwind and penetrate the food vacuole membranes. Food vacuoles disintegrate so that their contents (food bacteria) are found surrounded by the cytoplasm. Later there are present uncoiled R bodies in the cytoplasm and cytoplasmic blebs on the surface of the pellicle. At the same time affected paramecia become less motile, most probably due to the occlusion of cilia by the folds formed by the blebs round them and eventually by penetration of the cytoplasm into the cilia themselves. After prolonged treatment there are great accumulations of lipid droplets in the cytoplasm of sensitive animals. Kappa symbionts from the vacuolizing stock 562 cause rather similar prelethal symptoms. In addition, these kappa symbionts induce the macronuclei in sensitive paramecia to become spherical instead of elongated, their contents somewhat optically denser and the macronuclear envelope less discernible. Secondly, mitochondria undergo very noticeable necrotic changes in the case of treatment with stock 562 kappa symbionts and also to a lesser extent in stock 51. Furthermore, kappa toxin of stock 562 causes deciliation of affected sensitive paramecia and in later stages lipid droplets accumulate in the cytoplasm. It is suggested that the primary target of kappa toxins of both stocks are the biological membranes in various subcellular structures of sensitive paramecia. Copyright © 1978 Wiley‐Liss, Inc., A Wiley Company