Stochastic nucleoid segregation dynamics as a source of the phenotypic variability in E. coli

Area of Science:

• Microbiology
• Cell Biology
• Genetics

Background:

• Bacterial chromosome segregation is crucial for cell division.
• Cell-to-cell variability in bacterial populations arises from factors like gene expression noise and component partitioning.
• The role of internal stochasticity in segregation dynamics remains less understood.

Purpose of the Study:

• To investigate the sources of cell-to-cell variability in bacterial nucleoid segregation dynamics.
• To compare segregation variability in dividing versus filamentous *E. coli* cells.
• To determine if internal stochasticity of the segregation process contributes to phenotypic variability.

Main Methods:

• Utilized time-lapse microscopy to monitor nucleoid segregation in live *E. coli* cells.
• Grew cells in linear grooves to create dividing and filamentous lineages under identical conditions.
• Quantified segregation characteristics including synchrony, separation rates, and final positions.

Main Results:

• Gene expression noise was homogenized in filamentous cells compared to dividing cells.
• Nucleoid partitioning synchrony decreased over cell cycles, but less so in filamentous cells.
• Nucleoid segregation rates were similar between dividing and filamentous cells, with substantial variability in both.
• Variability in segregation distances increased over cell cycles, particularly in dividing cells.

Conclusions:

• Removing cellular boundaries between nucleoids reduces segregation dynamics variability.
• The inherent stochasticity within the nucleoid itself is a primary driver of segregation variability.
• Internal nucleoid dynamics contribute significantly to cell-to-cell phenotypic variation in bacteria.