Reconcile rrn operon colocalization with Hi-C contact patterns in E. coli

Determine how the spatial colocalization of rrn operons observed by fluorescence-based imaging in Escherichia coli can be reconciled with the absence of stable or long-lived contacts between distant genomic segments reported by Hi-C contact maps of the E. coli chromosome.

Background

In Escherichia coli, rrn operons are among the most transcriptionally active loci and have been reported to colocalize spatially in fluorescence-based imaging experiments, indicating that distant genomic regions tend to be closer together than expected based on contour distance alone.

However, ensemble Hi-C measurements in E. coli do not show stable or long-lived contacts between distant genomic segments, creating an apparent inconsistency between single-cell imaging observations and population-averaged contact maps. The paper frames this discrepancy as an explicit open question and develops a physical model to address it.

References

Reconciling these two experimental observations: the colocalization of {\em rrn operons} in imaging experiments and the absence of persistent contacts in Hi-C maps, remains an open question.

— Mechanistic insights into the spatial organization of RNA polymerase proteins and the chromosome in E. coli cells  (2604.02838 - Mitra et al., 3 Apr 2026) in Introduction, paragraph discussing rrn operon colocalization and Hi-C contacts (following the discussion of experimental techniques).