EXPERIMENTAL-ANALYSIS OF THE RESISTANCE OF PARAMECIUM-CAUDATUM (CILIOPHORA) AGAINST INFECTION BY BACTERIUM HOLOSPORA-UNDULATA

In some clones of Paramecium caudatum (to be referred to as ''resistan t'') infections forms of Holospora undulata bacteria which are capable of infecting the micronucleus were lysed within 3-4 h after invasion of the micronucleus. After microsurgical transplantation of the micron ucleus of non-resistant into resistant paramecia (without removal of t he recipient cell's micronucleus), bacteria were lysed in both micronu clei of the heterokaryon cell. They were not lysed in either micronucl eus when the micronucleus of a resistant cell was transplanted into a non-resistant one. After UV-microirradiation or microsurgical removal of the macronucleus from a resistant cell, lysis did not occur. The da ta suggest that the micronucleus, as an independent morphological stru cture, cannot by itself initiate bacterial lysis. On the basis of thes e results it is clear that the process of H. undulata lysis in the mic ronucleus of P. caudatum is mediated by the activity of the macronucle us.