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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.
Spores form a part of the life cycles of a diverse range of organisms such as many bacteria, plants, algae, fungi and some protozoa. In Saccharomyces cerevisiae (Kingdom Fungi), the set of early genes activating sporulation is induced by Ime1 (Inducer of Meiosis 1) and a regulator of middle genes is Ndt80p. [ 4 ]
Asexual cells may vary in shape. [13] The shape of the cell may be informative in terms of detecting mode of reproduction or taxonomic placement to genera or species. Although not commonly known, some species form endospores (e.g.Candida species). [2] These are asexual spores that are formed within their mother cell (hyphal or single cell).
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.
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]
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 ends up with twice as many copies of each chromosome per repeat of the S phase. [17] Endomitosis is a type of cell cycle variation where mitosis is initiated, but stopped during anaphase and thus cytokinesis is not completed. The cell ends up with multiple nuclei in contrast to a cell undergoing endoreduplication.
The term sporogenesis can also refer to endospore formation in bacteria, which allows the cells to survive unfavorable conditions. Endospores are not reproductive structures and their formation does not require cell fusion or division. Instead, they form through the production of an encapsulating spore coat within the spore-forming cell.