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In biology, a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. [1] Spores form part of the life cycles of many plants , algae , fungi and protozoa . [ 2 ]
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.
The process of endospore formation has profound morphological and physiological consequences: radical post-replicative remodelling of two progeny cells, accompanied eventually by cessation of metabolic activity in one daughter cell (the spore) and death by lysis of the other (the 'mother cell').
Endospore formation is not found among Archaea. [7] The endospore consists of the bacterium's DNA, ribosomes and large amounts of dipicolinic acid. Dipicolinic acid is a spore-specific chemical that appears to help in the ability for endospores to maintain dormancy. This chemical accounts for up to 10% of the spore's dry weight. [3]
As a model organism, B. subtilis is commonly used in laboratory studies directed at discovering the fundamental properties and characteristics of Gram-positive spore-forming bacteria. [29] In particular, the basic principles and mechanisms underlying formation of the durable endospore have been deduced from studies of spore formation in B ...
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However, both events (spore formation and fertilization) are necessary to complete sexual reproduction in the plant life cycle. Fungi and some algae can also utilize true asexual spore formation, which involves mitosis giving rise to reproductive cells called mitospores that develop into a new organism after dispersal.
These hyphae grow outward from the original spore, forming an expanding circle of mycelium. The circular shape of a fungal colony explains the formation of fairy rings, and also the circular lesions of skin-infecting fungi that cause ringworm. Some basidiospores germinate repetitively by forming small spores instead of hyphae.