1. Initiation:
- The initiation of DNA replication, marking the start of the cell cycle, is tightly regulated in bacteria.
- Typically, a single origin of replication (oriC) is present in the bacterial chromosome.
- Initiation involves the assembly of a multi-protein complex called the replisome at the oriC region.
- Factors like DnaA protein, which binds to specific DNA sequences, play crucial roles in triggering the initiation process.
2. Elongation:
- Once DNA replication begins, the unwinding of the DNA double helix occurs, forming a replication fork.
- DNA polymerases, the enzymes responsible for DNA synthesis, add new nucleotides to the growing DNA strands in the 5' to 3' direction.
- Multiple replication forks can exist simultaneously in bacteria, allowing rapid replication of the circular chromosome.
3. Termination:
- When the replication forks reach specific termination sequences (ter sites) on the chromosome, DNA replication comes to an end.
- Ter sequences act as signals for the replisome to disassemble, halting DNA synthesis.
4. Segregation and Partitioning:
- In bacteria, cell division occurs through binary fission, where the cell splits into two identical daughter cells.
- To ensure proper segregation of replicated DNA, bacteria utilize a range of proteins, including those involved in chromosome organization, segregation, and partitioning.
- These proteins organize and separate the duplicated chromosomes, directing them to opposite ends of the cell.
5. Cell Wall Synthesis and Septation:
- As DNA segregation and partitioning occur, the synthesis of new cell wall material takes place.
- Peptidoglycan, a major component of the bacterial cell wall, is synthesized and deposited to form a septum, dividing the cell into two compartments.
6. Cell Division:
- Once cell wall synthesis is complete, the septum pinches inward, leading to the physical separation of the two daughter cells.
- This division process is driven by bacterial cell division proteins and often involves interactions with cytoskeletal elements.
Throughout the cell cycle, bacteria utilize various regulatory mechanisms, such as checkpoints and DNA damage response systems, to ensure the accuracy and fidelity of DNA replication and cell division. These control mechanisms help maintain genetic stability and prevent the propagation of harmful mutations.
