Elimination of kappa particles from 'killer' strains of Paramecium aurelia by treatment with chloromycetin.

Abstract

CERTAIN strains of Paramecium, known as ‘killers’, contain in their cytoplasm particles, called ‘kappa particles’1, which are Feulgen-positive, and stain with Giemsa after acid hydrolysis2. Killers liberate into the culture medium a substance lethal to Paramecium not containing kappa particles, known as ‘sensitives’. Kappa particles have many of the properties of cytoplasmic genes3, but their size (0.2–0.5 µ in length), and their staining reactions, suggest that they may be parasitic micro-organisms3–5 such as the rickettsiae, viruses of the psittacosislymphogranuloma group, or even small bacteria.