Control of wall band splitting in Streptococcus faecalis

Area of Science:

• Microbiology
• Cell Biology
• Bacterial Growth Dynamics

Background:

• Understanding bacterial cell cycle regulation is crucial for comprehending growth and division.
• Streptococcus faecalis serves as a model organism for studying microbial cell division.

Purpose of the Study:

• To analyze the cell cycle of Streptococcus faecalis under different growth conditions.
• To estimate cell cycle phase durations and key timing parameters like pole time.
• To investigate the relationship between cell growth, DNA replication, and division.

Main Methods:

• Computerized reconstruction and analysis of whole-mounted, shadowed Streptococcus faecalis cells.
• Application of a novel method for estimating cell cycle phase durations and statistical parameters.
• Classification of cells based on septal radius, growth zones, and 'birth site' characteristics.

Main Results:

• Pole time was found to be only slightly greater than the mass doubling time in both slow and rapid growth conditions.
• In slow-growing cells, 69% of newborn cells lacked growth zones, compared to 16% or less in rapid growth.
• Dichotomous replication occurs, where new DNA synthesis rounds begin before previous ones complete, due to DNA synthesis duration exceeding mass doubling time.

Conclusions:

• Cell division is initiated when surface area expansion via growth zones cannot accommodate cytoplasmic production.
• Initiation of DNA replication and cell wall band splitting are not simultaneous events.
• The cell cycle regulation in Streptococcus faecalis involves complex coordination between growth, DNA replication, and division processes.