Editing Slime mold (section)

== Life cycle ==

=== Plasmodial slime molds ===

[[File:Physarum polycephalum strain LU352 - 4.jpg|thumb|Long strands of ''[[Physarum polycephalum]]'' streaming along as it forms a [[plasmodium (life cycle)|plasmodium]] with many nuclei without individual cell membranes ]]

Plasmodial slime molds begin life as [[amoeba]]-like [[cell (biology)|cells]]. These unicellular amoebae are commonly [[haploid]] and feed on small prey such as [[bacteria]], yeast cells, and fungal spores by [[phagocytosis]], engulfing them with its [[cell membrane]]. These amoebae can mate if they encounter the correct [[mating type]] and form [[zygote]]s that then grow into [[plasmodium (life cycle)|plasmodia]]. These contain many [[cell nucleus|nuclei]] without [[cell membranes]] between them, and can grow to meters in size. The species ''[[Fuligo septica]]'' is often seen as a slimy yellow network in and on rotting logs. The amoebae and the plasmodia engulf microorganisms.<ref name="Ling">{{cite web|url=http://npsnj.org/articles/myxomycetes.html |archive-url=https://web.archive.org/web/20150609104451/http://npsnj.org/articles/myxomycetes.html |archive-date=9 June 2015 |last=Ling |first=H. |date=2012 |title=Myxomycetes: Overlooked Native Plants |work=The Native Plant Society of New Jersey|access-date=29 May 2018}}</ref> The plasmodium grows into an interconnected network of protoplasmic strands.<ref>{{Cite web|url=http://www.hup.harvard.edu/catalog.php?isbn=978-0-674-97591-0 |title=Life at the Edge of Sight |last1=Chimileski |first1=Scott |last2=Kolter |first2=Roberto |publisher=Harvard University Press |website=www.hup.harvard.edu |access-date=2018-01-26 |archive-date=October 19, 2023 |archive-url=https://web.archive.org/web/20231019151352/http://www.hup.harvard.edu/catalog.php?isbn=978-0-674-97591-0}}</ref> Within each protoplasmic strand, the cytoplasmic contents rapidly stream, periodically reversing direction. The streaming protoplasm within a plasmodial strand can reach speeds of up to 1.35&nbsp;mm per second in ''Physarum polycephalum'', the fastest for any microorganism.<ref>{{cite book |last=Alexopoulos |first=C.J. |date=1962 |edition=Second |title=Introductory Mycology |location=New York, N.Y. |publisher=John Wiley and Sons |page=78 |url=https://archive.org/details/dli.ernet.286173}}</ref>

[[File:Plasmodial slime mold life cycle English.png|thumb|upright=1.75|Life cycle of a plasmodial slime mold. Haploid gametes undergo sexual fusion to form a diploid cell. Its nucleus divides (but the cell does not) to form a multinucleate plasmodium. [[Meiosis]] halves the number of [[chromosome]]s to form haploid cells with just one nucleus.<ref name="Dee 1960">{{Cite journal |last=Dee |first=Jennifer |date=1960 |title=A Mating-type System in an Acellular Slime-mould |journal=Nature |volume=185 |issue=4715 |pages=780–781 |doi=10.1038/185780a0 |bibcode=1960Natur.185..780D |s2cid=4206149}}</ref>]]

Slime molds are [[Isogamy|isogamous]], which means that their [[gamete]]s (reproductive cells) are all the same size, unlike the eggs and sperms of animals.<ref name="Moskvitch-2018">{{Cite web |url=https://www.quantamagazine.org/slime-molds-remember-but-do-they-learn-20180709/ |title=Slime Molds Remember – but Do They Learn? |last=Moskvitch |first=Katia |website=Quanta Magazine |date=9 July 2018 |access-date=2019-11-02}}</ref> ''[[Physarum polycephalum]]'' has three [[gene]]s involved in reproduction: ''mat''A and ''mat''B, with thirteen variants each, and ''mat''C with three variants. Each reproductively mature slime mold is [[diploid]], meaning that it contains two copies of each of the three reproductive genes.<ref name="Judson-2002">{{Cite book |last=Judson |first=Olivia |title=Dr. Tatiana's Sex Advice To All Creation |publisher=Henry Holt and Company |year=2002 |isbn=978-0-8050-6332-5 |location=New York |pages=187–193}}</ref> When ''P.&nbsp;polycephalum'' is ready to make its reproductive cells, it grows a bulbous extension of its body to contain them.<ref name="Renner-2006">{{Cite web |url=http://bioweb.uwlax.edu/bio203/2010/renner_brad/reproduction.htm |last=Renner |first=B. |date=2006 |title=Slime Mold Reproduction |work=BioWeb |publisher=University of Wisconsin System |access-date=2019-11-02 |archive-date=November 2, 2019 |archive-url=https://web.archive.org/web/20191102001509/http://bioweb.uwlax.edu/bio203/2010/renner_brad/reproduction.htm}}</ref> Each cell has a random combination of the genes that the slime mold contains within its [[genome]]. Therefore, it can create cells of up to eight different gene types. Released cells then independently seek another compatible cell for fusion. Other individuals of ''P. polycephalum'' may contain different combinations of the ''mat''A, ''mat''B, and ''mat''C genes, allowing over 500 possible variations. It is advantageous for organisms with this type of reproductive cell to have many mating types because the likelihood of the cells finding a partner is greatly increased, and the risk of [[inbreeding]] is drastically reduced.<ref name="Judson-2002" />

=== Cellular slime molds ===

{{further|Dictyostelid}}

The cellular slime molds are a group of approximately 150 described species. They occur primarily in the humus layer of forest soils<ref>{{Cite journal |last1=Cavender |first1=James C. |last2=Raper |first2=Kenneth B. |date=March 1965 |title=The Acrasieae in Nature. Ii. Forest Soil as a Primary Habitat |url=https://bsapubs.onlinelibrary.wiley.com/doi/10.1002/j.1537-2197.1965.tb06789.x |journal=American Journal of Botany |language=en |volume=52 |issue=3 |pages=297–302 |doi=10.1002/j.1537-2197.1965.tb06789.x |issn=0002-9122}}</ref> and feed on bacteria but also are found in animal dung and agricultural fields. They exist as single-celled organisms while food is plentiful. When food is in short supply, many of the single-celled amoebae congregate and start moving as a single body, called a 'slug'. The ability of the single celled organisms to aggregate into multicellular forms are why they are also called the social amoebae. In this state they are sensitive to airborne chemicals and can detect food sources. They readily change the shape and function of parts, and may form stalks that produce fruiting bodies, releasing countless spores, light enough to be carried on the wind or on passing animals.<ref name="Jacobson 2012">{{cite web |last=Jacobson |first=R. |date=April 5, 2012 |title=Slime Molds: No Brains, No Feet, No Problem |url=https://www.pbs.org/newshour/science/the-sublime-slime-mold |publisher=PBS Newshour}}</ref> The cellular slime mold ''[[Dictyostelium discoideum]]'' has many different mating types. When this organism has entered the stage of reproduction, it releases a chemical attractant.<ref name="Bonner-2009">{{Cite book |last=Bonner |first=J. T. |title=The Social Amoebae: The Biology of Cellular Slime Molds |date=2009 |publisher=Princeton University Press |isbn=978-0-691-13939-5 |jstor=j.ctt7s6qz |pages=}}</ref> When it comes time for the cells to fuse, ''Dictyostelium discoideum'' has mating types of its own that dictate which cells are compatible with each other. There are at least eleven mating types; [[macrocyst]]s form after cell contact between compatible mating types.<ref name="Erdos-1973">{{cite journal |last1=Erdos |first1=Gregory W. |last2=Raper |first2=Kenneth B. |last3=Vogen |first3=Linda K. |title=Mating Types and Macrocyst Formation in ''Dictyostelium discoideum'' |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=70 |issue=6 |pages=1828–1830 |date=June 1973 |pmid=16592095 |pmc=433606 |doi=10.1073/pnas.70.6.1828 |doi-access=free |bibcode=1973PNAS...70.1828E }}</ref>

==== Chemical signals ====

[[File:CAMP.svg|thumb|upright|The first [[acrasin]] to be discovered was [[cyclic adenosine monophosphate|cyclic AMP]], a small molecule common in cells. Acrasins are signals that cause cellular slime mold amoebae to aggregate.<ref name="Nestle Sussman 1972"/> ]]

The chemicals that aggregate cellular slime molds are small molecules called [[acrasin]]s; motion towards a chemical signal is called [[chemotaxis]]. The first acrasin to be discovered was [[cyclic adenosine monophosphate]] (cyclic AMP), a common cell signaling molecule, in ''Dictyostelium discoideum''. During the aggregation phase of their life cycle, ''Dictyostelium discoideum'' amoebae communicate with each other using traveling waves of cyclic AMP.<ref name="Nestle Sussman 1972">{{cite journal |last1=Nestle |first1=Marion |last2=Sussman |first2=Maurice |title=The effect of cyclic AMP on morphogernesis and enzyme accumulation in Dictyostelium discoideum |journal=Developmental Biology |volume=28 |issue=4 |pages=545–554 |date=August 1972 |pmid=4340352 |doi=10.1016/0012-1606(72)90002-4 }}</ref><ref>{{cite journal |last1=Levine |first1=Herbert |last2=Reynolds |first2=William |title=Streaming instability of aggregating slime mold amoebae |journal=Physical Review Letters |volume=66 |issue=18 |pages=2400–2403 |date=May 1991 |pmid=10043475 |doi=10.1103/PhysRevLett.66.2400 |bibcode=1991PhRvL..66.2400L }}</ref><ref>{{Cite journal |last1=Tyson |first1=John J. |last2=Alexander |first2=Kevin A. |last3=Manoranjan |first3=V. S. |last4=Murray |first4=J.D. |date=1989-01-01 |title=Spiral waves of cyclic amp in a model of slime mold aggregation |journal=Physica D: Nonlinear Phenomena |volume=34 |issue=1 |pages=193–207 |doi=10.1016/0167-2789(89)90234-0 |bibcode=1989PhyD...34..193T |issn=0167-2789}}</ref> There is an amplification of cyclic AMP when they aggregate.<ref>{{cite journal |last1=Roos |first1=W. |last2=Nanjundiah |first2=V. |last3=Malchow |first3=D. |last4=Gerisch |first4=G. |title=Amplification of cyclic-AMP signals in aggregating cells of Dictyostelium discoideum |journal=FEBS Letters |volume=53 |issue=2 |pages=139–142 |date=May 1975 |pmid=166875 |doi=10.1016/0014-5793(75)80005-6 |s2cid=29448450 }}</ref> Pre-stalk cells move toward cyclic AMP, but pre-spore cells ignore the signal.<ref>{{cite journal |last1=Fujimori |first1=Taihei |last2=Nakajima |first2=Akihiko |last3=Shimada |first3=Nao |last4=Sawai |first4=Satoshi |title=Tissue self-organization based on collective cell migration by contact activation of locomotion and chemotaxis |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=116 |issue=10 |pages=4291–4296 |date=March 2019 |pmid=30782791 |pmc=6410881 |doi=10.1073/pnas.1815063116 |bibcode=2019PNAS..116.4291F |doi-access=free }}</ref> Other acrasins exist; the acrasin for ''[[Polysphondylium violaceum]]'', purified in 1983, is the [[dipeptide]] glorin.<ref>{{Cite journal |last=Bonner |first=John Tyler |date=1983 |title=Chemical Signals of Social Amoebae |url=https://www.jstor.org/stable/24968880 |journal=[[Scientific American]] |volume=248 |issue=4 |pages=114–121 |doi=10.1038/scientificamerican0483-114 |jstor=24968880 |bibcode=1983SciAm.248d.114B |issn=0036-8733}}</ref> [[Calcium ion]]s too serve to attract slime mold amoebae, at least at short distances. It has been suggested that acrasins may be taxon-specific, since specificity is required to form an aggregation of genetically similar cells. Many dictyostelid species indeed do not respond to cyclic AMP, but as of 2023 their acrasins remained unknown.<ref name="Sheikh Fu Brown Baldauf 2023">{{citation | last1=Sheikh | first1=Sanea | last2=Fu | first2=Chengjie | last3=Brown | first3=Matthew | last4=Baldauf | first4=Sandra | title=Deep origins of eukaryotic multicellularity revealed by the Acrasis kona genome and developmental transcriptomes | date=1 March 2023 | doi=10.21203/rs.3.rs-2587723/v1}}</ref>