Although transcription is known to shape bacterial chromosome organization, it is unclear how small perturbations in transcriptional activity affect nucleoid structure and dynamics. We exposed Escherichia coli to sub-inhibitory concentrations of the antibiotic rifampicin and quantified the nucleoid organization from live-cell fluorescence imaging using structure factors and autocorrelation functions of time-resolved intensity fluctuations. At long timescales (over several generations), even low doses produced significant phenomenological changes in nucleoid organization and segregation, including delayed onset of the minimum in nucleoid density and reduced ribosome accumulation at the cell center. However, the immediate effects were minimal, indicating that RNAP numbers maintain homeostasis during the early stages of the drug treatment.
Amir et al. (2026) studied this question.