Editing Endospore (section)

==Structure==
[[File:Bakterien Sporen.png|thumb|260px|Variations in endospore morphology: (1,&nbsp;4)&nbsp;central endospore; (2,&nbsp;3,&nbsp;5)&nbsp;terminal endospore; (6)&nbsp;lateral endospore]]
Bacteria produce a single endospore internally. The spore is sometimes surrounded by a thin covering known as the [[exosporium]], which overlies the ''spore coat''. The spore coat, which acts like a [[sieve]] that excludes large toxic molecules like [[lysozyme]], is resistant to many toxic [[molecules]] and may also contain [[enzymes]] that are involved in [[germination]]. In ''[[Bacillus subtilis|Bacillus subtilus]]'' endospores, the spore coat is estimated to contain more than 70 coat proteins, which are organized into an inner and an outer coat layer.<ref name="Henriques&Moran_2007">{{cite journal | vauthors = Henriques AO, Moran CP Jr | title = Structure, assembly, and function of the spore surface layers | journal = Annu Rev Microbiol | volume = 61 | pages = 555–588 | date = 2007 | pmid = 18035610| doi = 10.1146/annurev.micro.61.080706.093224 }}</ref> The X-ray diffraction pattern of purified ''B. subtilis'' endospores indicates the presence of a component with a regular periodic structure, which Kadota and Iijima speculated might be formed from a keratin-like protein.<ref name="Kadota_Iijima_1965">{{cite journal | vauthors = Kadota H, Iijima K | title = The X-ray diffraction pattern of spores of ''Bacillus subtilis'' | journal = Agric Biol Chem | volume = 29 | issue = 1 | pages = 80–81 | date = 1965 | doi = 10.1080/00021369.1965.10858352| doi-access =  }}</ref> However, after further studies this group concluded that the structure of the spore coat protein was different from keratin.<ref name="Hiragi_etal_1967">{{cite journal | vauthors = Hiragi Y, Iijima K, and Kadota H | title = Hexagonal single crystal pattern from the spore coat of ''Bacillus subtilis'' | journal = Nature | volume = 215 | issue = 5097 | pages = 154–5 | date = 1967 | pmid = 4963432 | doi = 10.1038/215154a0 | bibcode = 1967Natur.215..154H | s2cid = 4160084 }}</ref> When the ''B. subtilis'' genome was sequenced, no ortholog of human keratin was detected.<ref>{{cite journal | vauthors = Kunst F et al. | title = The complete genome sequence of the gram-positive bacterium ''Bacillus subtilis'' | journal = Nature | volume = 390 | issue = 6657 | pages = 249–56 | date = 1997 | pmid = 9384377 | doi = 10.1038/36786 | doi-access = free | bibcode = 1997Natur.390..249K }}</ref> The ''cortex'' lies beneath the spore coat and consists of [[peptidoglycan]]. The ''core wall'' lies beneath the cortex and surrounds the [[protoplast]] or ''core'' of the endospore. The core contains the spore chromosomal DNA which is encased in [[chromatin]]-like proteins known as SASPs (small acid-soluble spore proteins), that protect the spore DNA from [[UV]] radiation and heat.  The core also contains normal cell structures, such as [[ribosome]]s and other [[enzymes]], but is not metabolically active.

Up to 20% of the dry weight of the endospore consists of [[calcium]] [[Dipicolinic acid|dipicolinate]] within the core, which is thought to stabilize the DNA. Dipicolinic acid could be responsible for the heat resistance of the spore, and calcium may aid in resistance to heat and oxidizing agents. However, mutants resistant to heat but lacking dipicolinic acid have been isolated, suggesting other mechanisms contributing to heat resistance are also at work.<ref>Prescott, L. (1993). ''Microbiology'', Wm. C. Brown Publishers, {{ISBN|0-697-01372-3}}.</ref> Small acid-soluble proteins (SASPs) are found in endospores. These proteins tightly bind and condense the DNA, and are in part responsible for resistance to UV light and DNA-damaging chemicals.<ref name=Cornell>{{cite web | title=Bacterial Endospores | publisher=Cornell University College of Agriculture and Life Sciences, Department of Microbiology | access-date=October 21, 2018 | url=http://micro.cornell.edu/research/epulopiscium/bacterial-endospores | archive-url=https://web.archive.org/web/20180615001904/https://micro.cornell.edu/research/epulopiscium/bacterial-endospores/ | archive-date=June 15, 2018 | url-status=live }}</ref>

Visualising endospores under light microscopy can be difficult due to the impermeability of the endospore wall to [[Endospore staining|dyes and stains]]. While the rest of a bacterial cell may stain, the endospore is left colourless. To combat this, a special stain technique called a [[Moeller stain]] is used. That allows the endospore to show up as red, while the rest of the cell stains blue. Another staining technique for endospores is the [[Schaeffer-Fulton stain]], which stains endospores green and bacterial bodies red. The arrangement of spore layers is as follows:
* Exosporium
* Spore coat
* Spore cortex
* Core wall