Presence of polyriboadenylate sequences in pulse-labeled RNA of Escherichia coli.

Pulse-labeled RNA isolated from E. coli cells grown on limiting phosphate medium and phosphate-containing medium was analyzed by oligo(dT)-cellulose chromatography and by Millipore binding assay for polyriboadenylate-containing RNA. Whereas poly(A)-containing RNA amounted to as much as 15% of the total pulse-labeled RNA from cells grown on limiting phosphate medium, pulse-labeled RNA from cells grown on phosphate medium gave values around 1.5%. Steady-state labeled RNA from cells grown on limiting phosphate medium contained 1.2% poly(A) RNA. The addition of poly(A) sequences appears to be post-transcriptional. These results strongly favor the view that bacterial mRNAs may contain poly(A) stretches.