E. coli is widely used for systems biology research; there exists a need, however, for tools that can be used to accurately and comprehensively measure expression dynamics in individual living cells. To address this we present a library of transcriptional fusions of gfp to each of about 2,000 different promoters in E. coli K12, covering the great majority of the promoters in the organism. Each promoter fusion is expressed from a low-copy plasmid. We demonstrate that this library can be used to obtain highly accurate dynamic measurements of promoter activity on a genomic scale, in a glucose-lactose diauxic shift experiment. The library allowed detection of about 80 previously uncharacterized transcription units in E. coli, including putative internal promoters within previously known operons, such as the lac operon. This library can serve as a tool for accurate, high-resolution analysis of transcription networks in living E. coli cells.
Bibliographical noteFunding Information:
We thank R. Rosenberg, H. Sberro, I. Alaluf, P. Bashkin, K. Pabbaraju and J. McClure for assistance, M.B. Elowitz, S. Falkow, S. Leibler, B. Wanner and all members of our laboratories for discussions. We thank the US National Institutes of Health, the Israel Science Foundation, Minerva, the Human Frontier Science Program and the Kahn Family Foundation for support.