10.5 Prokaryotic Cell Division
3 min read•june 14, 2024
Prokaryotic cell division is a fascinating process that showcases the simplicity and efficiency of bacterial reproduction. Through , a single cell splits into two identical daughters, ensuring genetic continuity and rapid population growth.
The process involves , , and formation. Key players like and the circular chromosome highlight the unique adaptations of prokaryotes for swift and effective reproduction in diverse environments.
Prokaryotic Cell Division
Binary fission in prokaryotes
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- Primary method of reproduction in prokaryotic cells divides a single cell into two genetically identical daughter cells
- Steps of binary fission:
- DNA replication
- Single circular chromosome replicated resulting in two identical copies
- Chromosome segregation
- Two copies of the chromosome separated and moved to opposite ends of the cell
- Process mediated by the , a structure composed of FtsZ proteins
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- and cell membrane grow inward from the cell periphery forming a
- Septum divides the cell into two compartments each containing one copy of the chromosome
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- Septum completed and the two daughter cells separate from each other
- DNA replication
- Entire process of binary fission is rapid often taking only 20-30 minutes in optimal conditions (E. coli)
FtsZ vs tubulin in cell division
- FtsZ proteins in prokaryotes
- Form the Z ring, a contractile ring that mediates chromosome segregation and septum formation
- Assemble into filaments that encircle the cell at the division site
- Provide force necessary for cell constriction and septum formation
- Regulated by various accessory proteins that control Z ring assembly and positioning (, )
- Tubulin proteins in eukaryotes
- Form the mitotic spindle, a structure that separates chromosomes during mitosis and meiosis
- Assemble into microtubules that attach to chromosomes and pull them apart
- Provide force necessary for chromosome segregation
- Similarities between FtsZ and tubulin
- Both are , enzymes that hydrolyze GTP to provide energy for their functions
- Both assemble into filamentous structures (Z ring and microtubules) essential for cell division
- Both are highly conserved across their respective domains of life (bacteria and eukaryotes)
- Differences between FtsZ and tubulin
- FtsZ found in prokaryotes, while tubulin found in eukaryotes
- FtsZ forms a single ring structure (Z ring), while tubulin forms a more complex spindle apparatus
- FtsZ involved in both chromosome segregation and septum formation, while tubulin primarily involved in chromosome segregation
Bacterial chromosome organization and replication
- Organization of bacterial chromosomes
- Prokaryotic cells typically have a single circular chromosome
- Chromosome condensed and supercoiled to fit inside the cell
- Chromosome attached to the cell membrane at a specific site called the ()
- DNA is concentrated in a region called the , which is not membrane-bound
- Replication of bacterial chromosomes
- Replication begins at the oriC and proceeds bidirectionally
- Two replication forks move in opposite directions around the circular chromosome
- Replication is semi-conservative
- Each strand of the original DNA molecule serves as a template for the synthesis of a new complementary strand
- As replication progresses, newly synthesized DNA continuously wound and supercoiled to maintain its compact structure
- Replication completed when the two replication forks meet at the , located opposite the oriC
- Replication begins at the oriC and proceeds bidirectionally
- Segregation of replicated chromosomes
- After replication, two copies of the chromosome separated and moved to opposite ends of the cell
- Process mediated by the Z ring and various DNA-binding proteins that help organize and position the chromosomes ()
- Proper segregation ensures each daughter cell receives one complete copy of the genetic material
Bacterial Cell Structure and Growth
- Cell wall
- Rigid structure surrounding the cell membrane
- Provides structural support and protection
- Composed of , a mesh-like polymer of sugars and amino acids
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- Final stage of cell division where the cytoplasm is divided
- Involves the formation of a septum and separation of daughter cells
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- Measure of how quickly a bacterial population increases in size
- Affected by factors such as nutrient availability, temperature, and pH
- Important for understanding bacterial ecology and pathogenicity
Key Terms to Review (24)
Bacterial growth rate: The bacterial growth rate refers to the speed at which a bacterial population increases over time, typically measured as a change in cell number or biomass. This rate is influenced by various factors, including nutrient availability, environmental conditions, and the intrinsic characteristics of the bacteria themselves. Understanding the bacterial growth rate is crucial for comprehending how bacteria proliferate and how they respond to changes in their surroundings.
Binary (prokaryotic) fission: Binary fission is a method of asexual reproduction in prokaryotes where a single cell divides into two genetically identical daughter cells. This process involves DNA replication, chromosome segregation, and cytokinesis.
Binary fission: Binary fission is a form of asexual reproduction in which a single organism divides into two identical daughter cells. This process is primarily observed in prokaryotic cells and is crucial for their growth and reproduction, enabling rapid population increases. It also plays a significant role in the study of cell division, contributing to our understanding of how organisms reproduce and evolve.
Cell separation: Cell separation refers to the process by which daughter cells are physically separated from each other after cell division. This is particularly important in prokaryotic cell division, where cells reproduce through a process called binary fission, resulting in two identical cells. Effective cell separation ensures that each new cell maintains its own integrity and can function independently, facilitating growth and reproduction.
Cell wall: A cell wall is a rigid layer that surrounds the cells of plants, fungi, bacteria, and archaea. It provides structural support and protection while also determining the shape of the cell.
Cell Wall: The cell wall is a rigid outer layer that surrounds the plasma membrane of plant cells, fungi, and some prokaryotic organisms. It provides structural support, protection, and helps maintain cell shape, acting as a barrier against external stresses and pathogens while also regulating the passage of substances in and out of the cell.
Chromosome segregation: Chromosome segregation is the process by which chromosomes are evenly distributed to daughter cells during cell division. This crucial step ensures that each new cell receives an identical set of chromosomes, maintaining genetic stability across generations. It is a fundamental aspect of both prokaryotic and eukaryotic cell division, with specific mechanisms adapted to the cellular structure and division methods of different organisms.
Cytokinesis: Cytokinesis is the process that follows cell division, where the cytoplasm of a parent cell is divided into two daughter cells, completing the overall cell division. This process is crucial for ensuring that each daughter cell receives a full set of organelles and sufficient resources to function effectively after mitosis or meiosis.
DNA replication: DNA replication is the biological process of producing two identical copies of a DNA molecule from a single original DNA strand. This process is crucial for cell division, ensuring that each new cell receives an exact copy of the genetic material. It is fundamental for both prokaryotic and eukaryotic organisms, facilitating growth, development, and repair by accurately duplicating the genetic instructions required for life.
FtsA: FtsA is a protein essential for bacterial cell division, specifically involved in the formation of the divisome, the protein complex that orchestrates cytokinesis. It is a membrane-bound protein that plays a key role in recruiting other proteins necessary for the division process and helps to form the Z-ring at the future site of cell division, ensuring that the cell divides properly into two daughter cells.
FtsZ proteins: FtsZ proteins are essential cytoskeletal elements in prokaryotic cells that play a crucial role in cell division by forming a contractile ring at the future site of cytokinesis. These proteins are homologous to tubulin and assemble into filaments that help direct the process of septation, leading to the formation of two daughter cells during binary fission. FtsZ's ability to hydrolyze GTP provides the energy necessary for this dynamic assembly and disassembly, ensuring proper cell division.
GTPases: GTPases are a family of enzymes that hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP), playing crucial roles in cellular signaling and the regulation of various biological processes. These enzymes act as molecular switches, toggling between an active GTP-bound state and an inactive GDP-bound state, which is essential for prokaryotic cell division and other fundamental cellular functions.
Historical biogeography: Historical biogeography studies the distribution of species and ecosystems in geographic space and through geological time. It helps understand how current biodiversity patterns are influenced by past events such as continental drift, glaciation, and speciation.
Nucleoid: The nucleoid is a region within prokaryotic cells where the cell's circular DNA is located, playing a crucial role in cellular processes such as replication and gene expression. Unlike eukaryotic cells, which have a defined nucleus, prokaryotic cells have their genetic material concentrated in this non-membrane-bound area, allowing for efficient regulation of DNA functions in processes like cell division and adaptation.
OriC: oriC is the specific site on the circular DNA molecule of prokaryotic cells where DNA replication initiates. This origin of replication is crucial for cell division, as it allows the duplication of genetic material before a cell divides, ensuring that each daughter cell receives an identical copy of the genome.
Origin: The origin is the specific location on a chromosome where DNA replication begins. In prokaryotic cells, this site is called the origin of replication or oriC.
Origin of replication: The origin of replication is a specific location on a DNA molecule where the process of DNA replication begins. This region is crucial because it serves as the starting point for DNA unwinding and the synthesis of new DNA strands, ensuring that genetic information is accurately copied during cell division. The presence and functionality of the origin of replication are key features in both prokaryotic and eukaryotic organisms, impacting how they manage their genetic material during cell division and replication.
ParABS system: The ParABS system is a molecular mechanism used by many prokaryotic cells to ensure the correct segregation of plasmids during cell division. It involves a set of proteins, including ParA, ParB, and a centromere-like region on the plasmid, which work together to facilitate the movement and positioning of plasmids within the daughter cells. This system is crucial for maintaining genetic stability and is integral to the process of prokaryotic cell division.
Peptidoglycan: Peptidoglycan is a polymer that forms a mesh-like structure in the cell wall of most bacteria, providing strength and rigidity to the cell. It consists of sugars and amino acids, allowing it to maintain the shape of the bacterial cell and protect it from external stressors. This unique structure is crucial for distinguishing between different types of prokaryotic cells and plays a vital role in their survival and replication.
Septum: A septum is a dividing wall or membrane in an organism. It can be found in various biological structures and plays a key role in cell division and structure.
Septum formation: Septum formation is the process by which a dividing prokaryotic cell develops a partition that separates the two daughter cells during cell division. This essential step ensures that each daughter cell receives the necessary components, such as genetic material and cytoplasmic contents, to function properly after division. The formation of the septum is critical in prokaryotic cell division, primarily through binary fission, where the cell elongates and divides into two identical cells.
Terminus region: The terminus region refers to the specific area at the end of a linear DNA molecule where replication and cell division processes are regulated in prokaryotic cells. This region plays a crucial role in ensuring that the DNA is accurately replicated and properly segregated during cell division, contributing to genetic stability and cellular function.
Z ring: The Z ring is a key structure in prokaryotic cell division, acting as a dynamic scaffold that forms during cytokinesis. It is composed of the protein FtsZ, which polymerizes to create a ring-like structure at the future site of cell division, guiding the inward constriction of the cell membrane. This structure is essential for ensuring that the cell divides accurately and symmetrically, facilitating the equal distribution of genetic material into daughter cells.
ZipA: ZipA is a membrane-associated protein that plays a crucial role in prokaryotic cell division, specifically in the process of forming the septum that separates daughter cells. It acts as an anchor for the divisome complex, which is essential for cytokinesis, facilitating the interaction between the inner membrane and other proteins involved in the division process. Understanding ZipA's function helps clarify how prokaryotic cells successfully complete cell division despite their simpler cellular architecture.