Average rate of transcription elongation in E. coli is about
Quantitative in vitro transcription and live-cell imaging using fluorescent reporter systems measure bacterial RNA polymerase elongation speed. Under physiological ionic strength, temperature 37°C, and saturating rNTP concentrations, average velocity approximately 40 nucleotides per second, though variable due to ubiquitous pausing induced by DNA sequences, regulatory proteins NusA, and nascent RNA secondary structures. This rate accommodates coupling with translation elongation ~15 amino acids per second maintaining ribosome behind polymerase. Compared to DNA polymerase 800 nt/s, slower speed allows proofreading and regulation. Value widely accepted in molecular microbiology textbooks describing E. coli transcription kinetics.
Ref: Watson Chapter 13: Average transcription elongation rate E coli 40 nt/s; Alberts Chapter 6: Transcription kinetics measurements; Berg Chapter 28