Characterization of chloramphenicol- and 8-azaguanine-resistant mutants isolated from a continuous rat-liver epithelial cell line.

2 non-tumorigenic, chloramphenicol- and 8-azaguanine-resistant strains have been isolated from the rat-liver cell line K-22, by a 2-step mutagenesis procedure. Their chromosome composition and growth properties have been characterized. Failure of chloramphenicol to inhibit mitochondrial protein synthesis in one of the clones, F1, strongly suggests that resistance to the antibiotic in this strain is due to a mutation in mitochondrial DNA.