title: Isolation and characterization of nocardia-like variants of Mycobacterium smegmatis.
abstract: Orange-red-pigmented (OR) colonies were isolated from cream-yellow-pigmented Mycobacterium smegmatis after exposure to either mycobacteriophage MC4 or ultraviolet light; these variant strains were designated OR4 and ORuv, respectively. Early subculture of OR-colonies did not show any segregation of parental-type cells. However, colonies resembling the parental strains, possibly representing a back mutant (REV-OR4), were occasionally found during subculture of established OR-colonies or upon treatment with N-nitrose-N'-nitro-N-methylguanidine. The OR-variants were characterized by their lytic response to nocardiophage, but not to mycobacteriophages, presence of alpha-branched, beta-hydroxylated fatty acids of the Nocardia-type, and a guanine plus cytosine value of deoxyribonucleic acid (DNA) between 62 and 64 mol%. They were more resistant to the lethal action of both ultraviolet light and mitomycin C treatment than the parental and back mutant strains. Although the OR-variants in this study possess characteristics common to the genus Nocardia or some of the 'rhodochrous' mycobacteria, evidence is presented that they form a new class of mycobacterial variants.
mesh_terms: D005227:Fatty Acids / Q000096:biosynthesis; D014644:Genetic Variation; D008937:Mitomycins / Q000494:pharmacology; D009160:Mycobacteriophages / Q000254:growth & development; D009161:Mycobacterium / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D010860:Pigments, Biological / Q000096:biosynthesis; D014170:Transformation, Genetic; D014466:Ultraviolet Rays
chemical_list: D005227:Fatty Acids; D008937:Mitomycins; D010860:Pigments, Biological