FIG. 6.

Primer extension assay of DsrA stability in an hfq-1 strain. Cells were grown at 30°C in LB broth to an OD₆₀₀ of 0.5 and treated with rifampin to block new transcription. Samples were taken at the indicated times, and RNA was extracted. DsrA was detected using a primer extension assay and DsrA-specific primers. Lanes marked with a minus sign contain RNA isolated from a dsrA deletion mutant. (A) DsrA expressed from a plasmid and the chromosome. (B) DsrA expressed only from the chromosome. Note that the chromosome- and plasmid-expressed dsrA genes have the same transcription start site. Only the chromosome-expressed DsrA has a decreased half-life in the Hfq⁻ host.