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Abstract

THE reproduction of RNA-containing bacteriophages is independent of host DNA and DNA-synthesis1–4. An understanding of the underlying processes thus should lead either to the detection of a double-stranded form of RNA, which would be an analogue to the replicative form of single-stranded DNA5, or to a novel mode of single-strand replication. To check for an RNA-intermediate of phage-RNA replication, extracts were prepared from E. coli cells infected with the RNA-containing phage ƒr (refs. 6–8), On stepwise elution9 from a methylated albumin (MAK) column10, two RNA-fractions separated which were not detected in extracts from non-infected bacteria: one fraction, eluting at 0.70 M sodium chloride, resembled the RNA extracted from purified ƒr-particles. The other fraction, eluting at 0.60 M sodium chloride, will be designated at 0.6–RNA and was prominent by its resistance towards digestion with RNase.