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An endospore stain of the cell Bacillus subtilis showing endospores as green and the vegetative cell as redPhase-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.[1][2] The name "endospore" is suggestive of a spore or seed-like form (endo means 'within'), but it is not a true spore (i.e., not an offspring). It is a stripped-down, dormant form to which the bacterium can reduce itself. Endospore formation is usually triggered by a lack of nutrients, and usually occurs in gram-positive bacteria. In endospore formation, the bacterium divides within its cell wall, and one side then engulfs the other.[3] Endospores enable bacteria to lie dormant for extended periods, even centuries. There are many reports of spores remaining viable over 10,000 years, and revival of spores millions of years old has been claimed. There is one report of viable spores of Bacillus marismortui in salt crystals approximately 25 million years old.[4][5] When the environment becomes more favorable, the endospore can reactivate itself into a vegetative state. Most types of bacteria cannot change to the endospore form. Examples of bacterial species that can form endospores include Bacillus cereus, Bacillus anthracis, Bacillus thuringiensis, Clostridium botulinum, and Clostridium tetani.[6] 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]
Endospores can survive without nutrients. They are resistant to ultraviolet radiation, desiccation, high temperature, extreme freezing and chemical disinfectants. Thermo-resistant endospores were first hypothesized by Ferdinand Cohn after studying Bacillus subtilis growth on cheese after boiling the cheese. His notion of spores being the reproductive mechanism for the growth was a large blow to the previous suggestions of spontaneous generation. Astrophysicist Steinn Sigurdsson said "There are viable bacterial spores that have been found that are 40 million years old on Earth – and we know they're very hardened to radiation."[8] Common antibacterial agents that work by destroying vegetative cell walls do not affect endospores. Endospores are commonly found in soil and water, where they may survive for long periods of time. A variety of different microorganisms form "spores" or "cysts", but the endospores of low G+C gram-positive bacteria are by far the most resistant to harsh conditions.[3]
Some classes of bacteria can turn into exospores, also known as microbial cysts, instead of endospores. Exospores and endospores are two kinds of "hibernating" or dormant stages seen in some classes of microorganisms.
Formation of an endospore through the process of sporulation.
^Murray, Patrick R.; Ellen Jo Baron (2003). Manual of Clinical Microbiology. Vol. 1. Washington, D.C.: ASM.
^C. Michael Hogan (2010). "Bacteria". In Sidney Draggan; C.J. Cleveland (eds.). Encyclopedia of Earth. Washington DC: National Council for Science and the Environment. Archived from the original on 2011-05-11.
^ abcCite error: The named reference Cornell was invoked but never defined (see the help page).
^Cano, RJ; Borucki, MK (1995). "Revival and identification of bacterial spores in 25- to 40-million-year-old Dominican amber". Science. 268 (5213): 1060–1064. Bibcode:1995Sci...268.1060C. doi:10.1126/science.7538699. PMID 7538699.
^Ringo, John (2004). "Reproduction of Bacteria". Fundamental Genetics. pp. 153–160. doi:10.1017/CBO9780511807022.018. ISBN 9780511807022.
^"endospore" at Dorland's Medical Dictionary
^Madigan, Michael T.; Bender, Kelly S.; Buckley, Daniel H.; Sattley, W. Matthew; Stahl, David A. (2018). "Microbial Cell Structure and Function". Brock Biology of Microorganisms. p. 92. ISBN 9781292235103.
^BBC Staff (23 August 2011). "Impacts 'more likely' to have spread life from Earth". BBC. Archived from the original on 24 August 2011. Retrieved 2011-08-24.
An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive...
Endospore staining is a technique used in bacteriology to identify the presence of endospores in a bacterial sample. Within bacteria, endospores are protective...
Bacilli is a taxonomic class of bacteria that includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens such as Bacillus...
structures called endospores. Endospores develop within the cytoplasm of the cell; generally, a single endospore develops in each cell. Each endospore contains...
Bacillus, B. subtilis is rod-shaped, and can form a tough, protective endospore, allowing it to tolerate extreme environmental conditions. B. subtilis...
responsible for the pathogenicity. It forms a protective layer called endospore by which it can remain inactive for many years and suddenly becomes infective...
made primarily of lipopolysaccharide. Endospore staining is used to identify the presence or absence of endospores, which make bacteria very difficult to...
dormant endospore. B. subtilis can divide symmetrically to make two daughter cells (binary fission), or asymmetrically, producing a single endospore that...
Bacillus can reduce themselves to oval endospores and can remain in this dormant state for years. The endospore of one species from Morocco is reported...
disease is an international health problem, as C. tetani endospores are ubiquitous. Endospores can be introduced into the body through a puncture wound...
Belgian biology professor Emile van Ermengem published his finding of an endospore-forming organism he isolated from spoiled ham. Biologists classified van...
sporogenesis can also refer to endospore formation in bacteria, which allows the cells to survive unfavorable conditions. Endospores are not reproductive structures...
in environmental samples. It is unknown if these are able to produce endospores. Archaea and bacteria are generally similar in size and shape, although...
scheme for the taxonomic classification of bacteria, and to discover endospores. Louis Pasteur and Robert Koch were contemporaries of Cohn, and are often...
and like other members of the genus Bacillus, can produce protective endospores. They have a wide range of virulence factors, including phospholipase...
the best known bacterial adaptation to stress is the formation of endospores. Endospores are bacterial survival structures that are highly resistant to many...
counterstain. Malachite green is also used in endospore staining, since it can directly stain endospores within bacterial cells; here a safranin counterstain...
fragmentation, or budding; unlike bacteria, no known species of Archaea form endospores. The first observed archaea were extremophiles, living in extreme environments...
reduction or go further to achieve sterilization, which includes killing of endospores. Pasteurization-equivalent HPP can be done in chilled temperatures, while...
botulism after consuming honey contaminated with Clostridium botulinum endospores. Infantile botulism shows geographical variation. In the UK, only six...
and the inner layer is the endospore. The perispore is the thickest of the three layers while the exospore and endospore are relatively equal in width...
around for long periods of time. Gemmules are analogous to a bacterium's endospore and are made up of amoebocytes surrounded by a layer of spicules and can...
chemical compound which plays a role in the heat resistance of bacterial endospores. It is also used to prepare dipicolinato ligated lanthanide and transition...
the body. Septations develop and form endospores within the spherule. Rupture of spherules release these endospores, which in turn repeat the cycle and...
Sporosarcina contaminans is a Gram-positive and endospore-forming bacterium from the genus of Sporosarcina which has been isolated from an industrial...
nuclei red. This is the classic counterstain in both Gram stains and endospore staining. It can also be used for the detection of cartilage, mucin and...
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