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An endospore stain of the cell Bacillus subtilis showing endospores as green and the vegetative cell as red Phase-bright endospores of Paenibacillus alvei imaged with phase-contrast microscopy. An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota.
Endospores can last for decades in multiple hard conditions, such as drying and freezing. This is because the DNA inside the endospore can survive over a long period. Most bacteria are unable to form endospores due to their high resistance, but some common species are the genera Bacillus ( over 100 species) and Clostridium (over 160 species). [2]
Clostridium species are endospore-forming bacteria, and can survive in atmospheric concentrations of oxygen in this dormant form. The remaining bacteria listed do not form endospores. [5] Several species of the Mycobacterium, Streptomyces, and Rhodococcus genera are examples of obligate anaerobe found in soil. [10]
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
Some genera of Gram-positive bacteria, such as Bacillus, Clostridium, Sporohalobacter, Anaerobacter, and Heliobacterium, can form highly resistant, dormant structures called endospores. [93] Endospores develop within the cytoplasm of the cell; generally, a single endospore develops in each cell. [94]
The cell cycle is a cycle rather than a linear process because the two daughter cells produced repeat the cycle. This process contains two main phases, interphase , in which the cell grows and synthesizes a copy of its DNA, and the mitotic (M) phase, during which the cell separates its DNA and divides into two new daughter cells. [ 7 ]
Compared to the eukaryotic cell cycle, the prokaryotic cell cycle (known as binary fission) is relatively simple and quick: the chromosome replicates from the origin of replication, a new membrane is assembled, and the cell wall forms a septum which divides the cell into two. [7]
The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA replication or S phase, and the actual process of cell division, mitosis or M phase. [ 1 ]