THE BIOLOGICAL STATUS OF LAMBDA AND RELATED PARTICLES IN PARAMECIUM AURELIA

Abstract
Lambda particles, obtained from axenically grown P. aurelia, stock 299 (killers), can be cultivated in vitro in a medium containing 17 amino acids, 8 vitamins, guanosine-mono-phosphate, uridine-mono-phosphate, stigmasterol, a fraction obtained from yeast, edamine S, glycerol, and maltose. Folic acid is not required. The in vitro grown particles have retained their killing ability and can, under appropriate conditions, infect sensitive P. aurelia of stock 299. It is concluded that these particles are bacterial endosymbiotes of P. aurelia, stock 299.