[Experimental infection of an invertebrate cell line with a mollicute-like procaryote inducing the "lethargy of coleoptera" (author's transl)].

In vitro multiplication of a pathogenic intravacuolar mollicute-like procaryote from Melolontha melolontha L. was experimentally obtained in an insect cell line. The elongated and pleomorphic forms observed in the insect-host are reproduced in cell cultures. A third peculiar giant form is missing, showing that it does not play any role in the multiplication of the germ. The intrinsic potentialities of the germ are maintained during the successive passages, as proved by reinfection of the insect and by immunology. The original syndrome including the giant form is reproduced in the insect. The immunserum prepared from the wild germ isolated by density gradient is positive with the in vitro mollicute. The germs are intravacuolar, both in the cultured cells and in the insect host. Clearly the microorganism multiplies within the vacuoles. A cytopathogenic effect is noticed in the cultured cells overcrowed with germs. The germs become extracellular when they are released in the culture medium by disaggregation of the cell membranes. It seems that this work shows the first model of an intravacuolar mollicute-like procaryote experimentally multiplied in cultivated cells.