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Buoyant density, growth rate, and the cell cycle in Streptococcus faecium
1Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Journal of Bacteriology
|February 1, 1989
Summary
Buoyant density in Streptococcus faecium cells changes during the cell cycle, unlike in Escherichia coli. Increased cell density correlates with cell growth and new cell wall site initiation.
Area of Science:
- Microbiology
- Cell Biology
- Biophysics
Background:
- Buoyant density in rapidly growing Streptococcus faecium cells exhibits cell cycle-dependent variations.
- This behavior contrasts with that observed in Escherichia coli, suggesting unique regulatory mechanisms in S. faecium.
Purpose of the Study:
- To investigate the cell cycle-dependent changes in buoyant density of Streptococcus faecium.
- To correlate buoyant density variations with cell volume, cell wall growth sites, and growth rate.
Main Methods:
- Buoyant density was measured using Percoll density gradients.
- Cell volume was determined electronically.
- Cell wall growth site distribution was analyzed via electron microscopy.
Main Results:
- Mean population density and its variation increased with growth rate.
- Within populations, cell volume increased with density.
- Density changes correlated with cell cycle stage, cell size, and initiation of new cell wall growth sites, especially at faster growth rates.
Conclusions:
- The rate of buoyant density increase during the cell cycle in S. faecium correlates with the initiation of new cell wall growth sites.
- These findings highlight a potential regulatory link between cell density and cell wall synthesis in bacterial growth.