Cryptobiosis#Anhydrobiosis

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File:Tardigrade anhydrobiosis cycle.svgs draw in their legs and go into a cryptobiotic 'tun' state. They quickly revive when re-wetted.]]

Cryptobiosis or anabiosis is a metabolic state in extremophilic organisms in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all measurable metabolic processes stop, preventing reproduction, development, and repair. When environmental conditions return to being hospitable, the organism will return to its metabolic state of life as it was prior to cryptobiosis.

Forms

= Anhydrobiosis =

File:Desiccation-Tolerance-in-the-Tardigrade-Richtersius-coronifer-Relies-on-Muscle-Mediated-Structural-pone.0085091.s001.ogv]]

Anhydrobiosis is the most studied form of cryptobiosis and occurs in situations of extreme desiccation. The term anhydrobiosis derives from the Greek for "life without water" and is most commonly used for the desiccation tolerance observed in certain invertebrate animals such as bdelloid rotifers, tardigrades, brine shrimp, nematodes, and at least one insect, a species of chironomid (Polypedilum vanderplanki). However, other life forms exhibit desiccation tolerance. These include the resurrection plant Craterostigma plantagineum,{{Cite journal | last1 = Bartels | first1 = Dorothea | last2 = Salamini | first2 = Francesco | doi = 10.1104/pp.010765 | title = Desiccation Tolerance in the Resurrection Plant Craterostigma plantagineum. A Contribution to the Study of Drought Tolerance at the Molecular Level | journal = Plant Physiology | volume = 127 | issue = 4 | pages = 1346–1353 |date=December 2001 | pmid = 11743072 | pmc =1540161 }} the majority of plant seeds, and many microorganisms such as bakers' yeast.{{Cite journal | last1 = Calahan | first1 = Dean | last2 = Dunham | first2 = Maitreya | last3 = DeSevo | first3 = Chris | last4 = Koshland | first4 = Douglas E | doi = 10.1534/genetics.111.130369 | title = Genetic analysis of desiccation tolerance in Sachharomyces cerevisiae | journal = Genetics | volume = 189 | issue = 2 | pages = 507–519 |date=October 2011 | pmid = 21840858 | pmc=3189811}} Studies have shown that some anhydrobiotic organisms can survive for decades, even centuries, in the dry state.{{Cite journal | last1 = Shen-Miller | first1 = J | last2 = Mudgett | first2 = Mary Beth | last3 = Schopf | first3 = J William | last4 = Clarke | first4 = Steven | last5 = Berger | first5 = Rainer | doi = 10.2307/2445863 | title = Exceptional seed longevity and robust growth: Ancient sacred lotus from China | journal = American Journal of Botany | volume = 82 | issue = 11 | pages = 1367–1380 |date=November 1995| jstor = 2445863 }}

Invertebrates undergoing anhydrobiosis often contract into a smaller shape and some proceed to form a sugar called trehalose, a disaccharide consisting of two molecules of glucose with high water retention capabilities. Desiccation tolerance in plants is associated with the production of another sugar, sucrose. These sugars are thought to protect the organism from desiccation damage.{{Cite journal | last1 = Erkut | first1 = Cihan | last2 = Penkov | first2 = Sider | last3 = Fahmy | first3 = Karim | last4 = Kurzchalia | first4 = Teymuras V | doi = 10.4161/worm.19040 | title = How worms survive desiccation: Trehalose pro water | journal = Worm | volume = 1 | issue = 1 | pages = 61–65 |date=January 2012 | pmid = 24058825 | pmc=3670174}} In some creatures, such as bdelloid rotifers, no trehalose has been found, which has led scientists to propose other mechanisms of anhydrobiosis, possibly involving intrinsically disordered proteins.{{Cite journal | last1 = Tunnacliffe | first1 = Alan | last2 = Lapinski | first2 = Jens | last3 = McGee | first3 = Brian | doi = 10.1007/s10750-005-4239-6 | title = A putative LEA protein, but no trehalose, is present in anhydrobiotic bdelloid rotifers | journal = Hydrobiologia | volume = 546 | issue = 1 | pages = 315–321 |date=September 2005 | bibcode = 2005HyBio.546..315T | s2cid = 13072689 }}

In 2011, Caenorhabditis elegans, a nematode that is also one of the best-studied model organisms, was shown to undergo anhydrobiosis in the dauer larva stage.{{Cite journal | last1 = Erkut | first1 = Cihan | last2 = Penkov | first2 = Sider | last3 = Khesbak | first3 = Hassan | last4 = Vorkel | first4 = Daniela | last5 = Verbavatz | first5 = Jean-Marc | last6 = Fahmy | first6 = Karim | last7 = Kurzchalia | first7 = Teymuras V | doi = 10.1016/j.cub.2011.06.064 | title = Trehalose renders the dauer larva of Caenorhabditis elegans resistant to extreme desiccation | journal = Current Biology | volume = 21 | issue = 15 | pages = 1331–1336 |date=August 2011 | pmid = 21782434| s2cid = 18145344 | doi-access = free | bibcode = 2011CBio...21.1331E }} Further research taking advantage of genetic and biochemical tools available for this organism revealed that in addition to trehalose biosynthesis, a set of other functional pathways is involved in anhydrobiosis at the molecular level.{{Cite journal | last1 = Erkut | first1 = Cihan | last2 = Vasilj | first2 = Andrej | last3 = Boland | first3 = Sebastian | last4 = Habermann | first4 = Bianca | last5 = Shevchenko | first5 = Andrej | last6 = Kurzchalia | first6 = Teymuras V | doi = 10.1371/journal.pone.0082473 | title = Molecular strategies of the Caenorhabditis elegans dauer larva to survive extreme desiccation | journal = PLOS ONE | volume = 8 | issue = 12 | pages = e82473 |date=December 2013 | pmid = 24324795 | pmc=3853187| bibcode = 2013PLoSO...882473E | doi-access = free }} These are mainly defense mechanisms against reactive oxygen species and xenobiotics, expression of heat shock proteins and intrinsically disordered proteins as well as biosynthesis of polyunsaturated fatty acids and polyamines. Some of them are conserved among anhydrobiotic plants and animals, suggesting that anhydrobiotic ability may depend on a set of common mechanisms. Understanding these mechanisms in detail might enable modification of non-anhydrobiotic cells, tissues, organs or even organisms so that they can be preserved in a dried state of suspended animation over long time periods.

As of 2004, such an application of anhydrobiosis is being applied to vaccines.{{needs update inline|date=March 2025}} In vaccines, the process can produce a dry vaccine that reactivates once it is injected into the body. In theory, dry-vaccine technology could be used on any vaccine, including live vaccines such as the one for measles. It could also potentially be adapted to allow a vaccine's slow release, eliminating the need for boosters. This proposes to eliminate the need for refrigerating vaccines, thus making dry vaccines more widely available throughout the developing world where refrigeration, electricity, and proper storage are less accessible.{{cite news |url=http://news.bbc.co.uk/2/hi/health/3754504.stm |work=BBC News |title=High hopes for fridge-free jabs | date=2004-10-19}}

Based on similar principles, lyopreservation has been developed as a technique for preservation of biological samples at ambient temperatures.{{Cite journal | last1 = Yang | first1 = Geer | last2 = Gilstrap | first2 = Kyle | last3 = Zhang |first3 = Aili | last4 = Xu | first4 = Lisa X. | last5 = He | first5 = Xiaoming | title = Collapse temperature of solutions important for lyopreservation of living cells at ambient temperature | doi = 10.1002/bit.22690 | pmid = 20148402 | journal = Biotechnology and Bioengineering | pages = 247–259 | date = 1 June 2010 | volume = 106 | issue = 2 | s2cid = 20748794 }}{{Cite journal | last1 = Chakraborty | first1 = Nilay | last2 = Chang | first2 = Anthony | last3 = Elmoazzen | first3 = Heidi | last4 = Menze | first4 = Michael A. | last5 = Hand | first5 = Steven C. | last6 = Toner | first6 = Mehmet | doi = 10.1007/s10439-011-0253-1 | title = A Spin-Drying Technique for Lyopreservation of Mammalian Cells | journal = Annals of Biomedical Engineering | volume = 39 | issue = 5 | pages = 1582–1591 | year = 2011 | pmid = 21293974 | s2cid = 11204697 }} Lyopreservation is a biomimetic strategy based on anhydrobiosis to preserve cells at ambient temperatures. It has been explored as an alternative technique for cryopreservation. The technique has the advantages of being able to preserve biological samples at ambient temperatures, without the need for refrigeration or use of cryogenic temperatures.Yang G, Gilstrap K, Zhang A, Xu LX, He X. "Collapse temperature of solutions important for lyopreservation of living cells at ambient temperatures." Biotechnol Bioeng. 2010 Jun 1;106(2):247–259.Chakraborty N, Chang A, Elmoazzen H, Menze MA, Hand SC, Toner M. "A spin-drying technique for lyopreservation of mammalian cells". Ann Biomed Eng. 2011 May;39(5):1582–1591.

= Anoxybiosis =

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In situations lacking oxygen (a.k.a., anoxia), many cryptobionts (such as M. tardigradum) take in water and become turgid and immobile, but can survive for prolonged periods of time. Some ectothermic vertebrates and some invertebrates, such as brine shrimps,Clegg et al. 1999 copepods,Marcus et al., 1994 nematodes,Crowe and Cooper, 1971 and sponge gemmules,Reiswig and Miller, 1998 are capable of surviving in a seemingly inactive state during anoxic conditions for months to decades.

Studies of the metabolic activity of these idling organisms during anoxia have been mostly inconclusive. This is because it is difficult to measure very small degrees of metabolic activity reliably enough to prove a cryptobiotic state rather than ordinary metabolic rate depression (MRD). Many experts are skeptical of the biological feasibility of anoxybiosis, as the organism is managing to prevent damage to its cellular structures from the environmental negative free energy, despite being both surrounded by plenty of water and thermal energy and without using any free energy of its own. However, there is evidence that the stress-induced protein p26 may act as a protein chaperone that requires no energy in cystic Artemia franciscana (sea monkey) embryos, and most likely an extremely specialized and slow guanine polynucleotide pathway continues to provide metabolic free energy to the A. franciscana embryos during anoxic conditions. It seems that A. franciscana approaches but does not reach true anoxybiosis.{{Cite journal| last=Clegg | first=James S. |author-link=James S. Clegg | title=Cryptobiosis – a peculiar state of biological organization | doi=10.1016/S1096-4959(01)00300-1 | journal=Comparative Biochemistry and Physiology B | volume=128 | issue=4 | pages=613–624 | year=2001 | pmid=11290443}} {{closed access}}

= Chemobiosis =

Chemobiosis is the cryptobiotic response to high levels of environmental toxins. It has been observed in tardigrades.{{cite journal|last1=Møbjerg|first1=N.|last2=Halberg|first2=K. A.|last3=Jørgensen|first3=A.|last4=Persson|first4=D.|last5=Bjørn|first5=M.|last6=Ramløv|first6=H.|last7=Kristensen|first7=R. M.|title=Survival in extreme environments – on the current knowledge of adaptations in tardigrades|journal=Acta Physiologica|date=2011|volume=202|issue=3|pages=409–420|doi=10.1111/j.1748-1716.2011.02252.x|pmid=21251237|s2cid=20894284|url=https://www.researchgate.net/publication/49770874}}

= Cryobiosis =

Cryobiosis is a form of cryptobiosis that takes place in reaction to decreased temperature. Cryobiosis begins when the water surrounding the organism's cells has been frozen. Stopping molecule mobility allows the organism to endure the freezing temperatures until more hospitable conditions return. Organisms capable of enduring these conditions typically feature molecules that facilitate freezing of water in preferential locations while also prohibiting the growth of large ice crystals that could otherwise damage cells.{{cite journal |last1=Ali |first1=Farman |last2=Wharton |first2=David A. |title=Ice-Active Substances from the Infective Juveniles of the Freeze Tolerant Entomopathogenic Nematode, Steinernema feltiae |journal=PLOS ONE |volume=11 |issue=5 |date=26 May 2016 |pmid=27227961 |pmc=4882034 |doi=10.1371/journal.pone.0156502 |doi-access=free |page=e0156502|bibcode=2016PLoSO..1156502A }} Examples of such organisms include lobster{{cite web |url=http://www.sfgate.com/science/article/Frozen-Lobsters-Brought-Back-To-Life-2807663.php |title=Frozen Lobsters Brought Back to Life |date=18 March 2004}} and nematodes.{{cite journal |last1=Ali |first1=Farman |last2=Wharton |first2=DA |title=Cold tolerance abilities of two entomopathogenic nematodes, Steinernema feltiae and Heterorhabditis bacteriophora |journal=Cryobiology |date=2013 |volume=66 |pages=24–29 |doi=10.1016/j.cryobiol.2012.10.004 |pmid=23142823 |url=http://dx.doi.org/10.1016/j.cryobiol.2012.10.004}}{{cite journal |last1=Ali |first1=Farman |last2=Wharton |first2=DA |title=Intracellular Freezing in the Infective Juveniles of Steinernema feltiae: An Entomopathogenic Nematode |journal=PLOS ONE |date=2014 |volume=9 |issue=4 |pages=e94179 |doi=10.1371/journal.pone.0094179|doi-access=free |pmid=24769523 |pmc=4000207 |bibcode=2014PLoSO...994179A }}

= Osmobiosis =

Osmobiosis is the least studied of all types of cryptobiosis. Osmobiosis occurs in response to increased solute concentration in the solution the organism lives in. Little is known for certain, other than that osmobiosis appears to involve a cessation of metabolism.

Examples

The brine shrimp Artemia salina, which can be found in the Makgadikgadi Pans in Botswana,C. Michael Hogan (2008) [http://www.megalithic.co.uk/article.php?sid=22373&mode=&order=0Makgadikgadi, The Megalithic Portal, ed. A. Burnham] survives over the dry season when the water of the pans evaporates, leaving a virtually desiccated lake bed.

The tardigrade, or water bear, can undergo all five types of cryptobiosis. While in a cryptobiotic state, its metabolism reduces to less than 0.01% of what is normal, and its water content can drop to 1% of normal.Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press. It can withstand extreme temperature, radiation, and pressure while in a cryptobiotic state.Illinois Wesleyan University [http://www.iwu.edu/~tardisdp/tardigrade_facts.html Tardigrade Facts]

Some nematodes and rotifers can also undergo cryptobiosis.{{cite journal|last=Watanabe|first=Masahiko|title=Anhydrobiosis in invertebrates|journal=Appl. Entomol. Zool.|year=2006|volume=41|issue=1|pages=15–31|doi=10.1303/aez.2006.15|doi-access=free|bibcode=2006AppEZ..41...15W }}