Buoyant density variation during the cell cycle in microorganisms

Area of Science:

• Cell Biology
• Biophysics
• Evolutionary Biology

Background:

• Cell buoyant density is a biophysical property that can change during the cell cycle.
• Understanding cell density regulation provides insights into cellular homeostasis and evolution.

Purpose of the Study:

• To investigate the behavior of cell buoyant density across the cell cycle in diverse cell types.
• To determine if cell density regulation is conserved across different species and cell types.

Main Methods:

• Measurement of cell buoyant density using techniques like density gradient centrifugation.
• Analysis of cell density variation during the cell cycle in bacteria, yeast, and mammalian cells.
• Correlation of density changes with cell wall properties and growth conditions.

Main Results:

• Mean cell buoyant density was constant and independent of cell age in Escherichia coli, Schizosaccharomyces cerevisiae, Amoebae proteus, mouse lymphoma/myeloma cells, and Chinese hamster ovary cells.
• Cells with thick cell walls (e.g., budding yeast, Streptococcus faecium) exhibited variable buoyant density during the cell cycle.
• Cell buoyant density in E. coli is controlled by the osmoregulatory system, independent of growth rate.

Conclusions:

• Cell buoyant density is remarkably stable during the cell cycle in cells lacking heavy cell walls, indicating conserved regulatory mechanisms.
• Osmoregulatory systems likely control cell buoyant density, suggesting evolutionary conservation or convergent evolution of these mechanisms.
• The findings highlight the fundamental role of osmoregulation in maintaining cellular biophysical properties across diverse life forms.