Real-time RNA in a single cell

http://www.pnas.org/cgi/reprint/102/26/9160

Characterizing the dynamics of specific RNA levels requires realtime

RNA profiling in a single cell. We show that the combination

of a synthetic modular genetic system with fluorescence correlation

spectroscopy allows us to directly measure in real time the

activity of any specific promoter in prokaryotes. Using a simple

inducible gene expression system, we found that induced RNA

levels within a single bacterium of Escherichia coli exhibited a

pulsating profile in response to a steady input of inducer. The

genetic deletion of an efflux pump system, a key determinant of

antibiotic resistance, altered the pulsating transcriptional dynamics

and caused overexpression of induced RNA. In contrast with

population measurements, real-time RNA profiling permits identifying

relationships between genotypes and transcriptional dynamics

that are accessible only at the level of the single cell.