Feb 2, 2026

Basal Gene Expression Dynamics in Bacteria

Date: February 2, 2026 | 11:00 am – 12:30 pm
Speaker: Kirti Jain, ISTA
Location: Raiffeisen Lecture Hall
Language: English

The multiple antibiotic resistance (mar) operon is one of the largest regulons in Escherichia coli. The mar locus encodes an autorepressor, MarR; an autoactivator, MarA; and MarB, a protein of unknown function and via MarA regulates a wide variety of downstream targets involved in cellular processes such as efflux, pH response, porin regulation, etc. Although this system has been extensively studied for its role in antibiotic resistance, the role of basal expression has largely been overlooked and dismissed as promoter leakiness.

Our work explores the basal expression mode of the mar operon and shows that it is dynamic, consisting of rare stochastic gene expression pulses. These pulses maximize phenotypic variability in wild-type populations and, unexpectedly, transiently accelerate cellular elongation rates. At the molecular level, this behavior is linked to an unusual yet evolutionarily conserved GTG start codon in marR, suggesting that natural selection has preserved this dynamic expression pattern across many related gut bacteria. Together, these findings demonstrate that even so-called “leaky” uninduced gene expression can be a selected feature with meaningful ecological and physiological consequences, reshaping our understanding of gene regulation in microbes.