Cell wall damage increases macromolecular crowding effects in the Escherichia coli cytoplasm

Area of Science:

• Cell Biology
• Biophysics
• Microbiology

Background:

• The intracellular environment is densely packed with biomacromolecules, influencing their behavior.
• Macromolecular crowding affects biomolecule interactions, diffusion, and conformations.
• Intracellular crowding changes are typically attributed to biomacromolecule concentration variations.

Purpose of the Study:

• To investigate the role of spatial organization in macromolecular crowding effects.
• To determine if cell wall damage in Escherichia coli impacts cytoplasmic crowding.
• To elucidate the mechanisms behind altered crowding effects upon cell wall damage.

Main Methods:

• Utilized a genetically encoded macromolecular crowding sensor in Escherichia coli.
• Compared crowding effects in spheroplasts and penicillin-treated cells with hyperosmotic stress.
• Employed genetically encoded nucleic acid and DNA stains to assess cytoplasmic organization.
• Monitored conformational changes in a probe protein.

Main Results:

• Cell wall damage significantly increased cytoplasmic crowding effects in Escherichia coli, exceeding those from hyperosmotic stress.
• The observed crowding increase was independent of osmotic pressure, cell shape, or volume changes.
• Cytoplasmic mixing and nucleoid expansion were identified as potential causes for heightened crowding.
• Significant conformational changes were induced in a probe protein due to altered cytoplasmic organization.

Conclusions:

• Cell wall damage disrupts the normal biochemical organization of the Escherichia coli cytoplasm.
• Spatial reorganization, including cytoplasmic mixing and nucleoid expansion, plays a critical role in macromolecular crowding.
• These findings highlight a novel mechanism linking cell wall integrity to intracellular biophysical properties.