Pulsatile basal gene expression as a fitness determinant in bacteria

K. Jain (Corresponding author), R. Hauschild, O. O. Bochkareva, R. Roemhild, G. Tkačik, C. C. Guet (Corresponding author)

Publications: Contribution to journalArticlePeer Reviewed

Abstract

Active regulation of gene expression, orchestrated by complex interactions of activators and repressors at promoters, controls the fate of organisms. In contrast, basal expression at uninduced promoters is considered to be a dynamically inert mode of nonfunctional “promoter leakiness,” merely a byproduct of transcriptional regulation. Here, we investigate the basal expression mode of the mar operon, the main regulator of intrinsic multiple antibiotic resistance in Escherichia coli, and link its dynamic properties to the noncanonical, yet highly conserved start codon of marR across Enterobacteriaceae. Real-time, single-cell measurements across tens of generations reveal that basal expression consists of rare stochastic gene expression pulses, which maximize variability in wildtype and, surprisingly, transiently accelerate cellular elongation rates. Competition experiments show that basal expression confers fitness advantages to wildtype across several transitions between exponential and stationary growth by shortening lag times. The dynamically rich basal expression of the mar operon has likely been evolutionarily maintained for its role in growth homeostasis of Enterobacteria within the gut environment, thereby allowing other ancillary gene regulatory roles to evolve, e.g., control of costly-to-induce multidrug efflux pumps. Understanding the complex selection forces governing genetic systems involved in intrinsic multidrug resistance is crucial for effective public health measures.

Original languageEnglish
Article numbere2413709122
JournalProceedings of the National Academy of Sciences of the United States of America
Volume122
Issue number15
DOIs
Publication statusPublished - 7 Apr 2025

Austrian Fields of Science 2012

  • 106022 Microbiology

Keywords

  • basal expression
  • gene regulation
  • mar operon

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