As in several fields of molecular biology studies of E. coli have gives the model for subsequent investigations of transcription in eukaryotic cells. The basic mechanisms by that transcription is regulated were likewise elucidated by pioneering experiments in E. coli, in that regulated gene expression permits the cell to respond to variations in the environment, like as modifications in the availability of nutrients. The sympathetic of transcription in E. coli has thus gives the foundation for studies of the far more complex mechanisms which regulate gene expression in eukaryotic cells.