Bacterial nucleoid structure probed by active drag and resistive pulse sensing.

Area of Science:

• Biophysics
• Molecular Biology
• Genomics

Background:

• The bacterial nucleoid, the region containing the genome, is highly organized through complex biophysical forces.
• The DNA-binding protein H-NS (histone-like nucleoid structuring protein) is a key regulator of bacterial genome organization.

Purpose of the Study:

• To investigate the physical properties and size of purified bacterial nucleoids using advanced biophysical techniques.
• To elucidate the role of the H-NS protein in nucleoid compaction and bacterial adaptation to stationary phase.

Main Methods:

• Utilized a combination of a steerable optical trap and a high-throughput microcapillary Coulter counter for non-invasive, label-free analysis.
• Probed individual nucleoid physical properties and size with high throughput.
• Assessed nucleoid permeability to ion flow.

Main Results:

• Demonstrated the Coulter counter's capability to analyze individual nucleoid physical properties and size.
• Nucleoids from the Δhns mutant strain expanded approximately five-fold compared to wild-type (WT) bacteria in the stationary phase.
• Nucleoids exhibited behavior consistent with solid colloids regarding ion flow permeability.

Conclusions:

• H-NS protein is essential for maintaining nucleoid compaction, especially during the stationary phase.
• The findings highlight significant organizational changes in the bacterial genome as cells adapt to environmental conditions.
• The study provides new insights into the biophysical forces governing bacterial genome structure.