Difference between revisions of "Slime mold" - New World Encyclopedia

From New World Encyclopedia
Line 1: Line 1:
 
[[Image:Slime Mold Olympic National Park North Fork Sol Duc.jpg|thumb|right|240px|Slime mold from [[Olympic National Park]], USA (Possibly ''Physarum'')]]
 
[[Image:Slime Mold Olympic National Park North Fork Sol Duc.jpg|thumb|right|240px|Slime mold from [[Olympic National Park]], USA (Possibly ''Physarum'')]]
−
'''Slime mold''' is the common name for any of the members of a polyphyletic grouping of heterotrophic, [[fungi|fungi-like]] amoeboid (i.e. like an [[amoeba]]) organisms that have an [[Life cycle#Alternation of generations|alternation of generations]] [[life cycle]] where at some point separate single-celled [[protist]]s aggregate into a large swarm. There are two main forms. In '''plasmodial slime molds''' (Mycetozoa), the individual [[flagellum|flagellated]] cells fuse such as to make one large supercell with one large membrane surrounding numerous individual nuclei. In '''cellular slime molds''' (Acrasiomycota), the individual cells aggregate but retain their individual cell membranes. There are other groups listed as slime molds as well.  
+
'''Slime mold''' is the common name for any of the members of a polyphyletic grouping of heterotrophic, [[fungi|fungi-like]] amoeboid (i.e. like an [[amoeba]]) organisms that have an [[Life cycle#Alternation of generations|alternation of generations]] [[life cycle]] where at some point separate single-celled [[protist]]s aggregate into a large swarm. There are two main forms. In '''plasmodial slime molds''' (myxomycetes), the individual [[flagellum|flagellated]] cells fuse such as to make one large supercell with one large membrane surrounding numerous individual nuclei. In '''cellular slime molds''' (Acrasiomycota and Dictyostelida), the individual cells aggregate but retain their individual cell membranes. There are other groups listed as slime molds as well.  
  
 
While slime molds have a life cycle that resembles that of fungi, and once were classified in that group, they now are considered unrelated to the fungi and generally are classified with the [[Protista]].  
 
While slime molds have a life cycle that resembles that of fungi, and once were classified in that group, they now are considered unrelated to the fungi and generally are classified with the [[Protista]].  
  
 
The common name slime mold traces to the part of their life cycle in which their appearance can be gelatinous (hence the name slime). However, this fact mostly refers to the myxomycetes, which are the only macroscopic slime molds. They have been found all over the world feeding on microorganisms that live in any type of dead plant material. For this reason, it is very common to find these organisms growing in the soil, on lawns, and in the forest commonly on deciduous logs (hence the name [[molds]]). However, in tropical areas of the world, they also seem to be very common on [[inflorescences]], [[fruit|fruits]], and in aerial situations (i.e. in the canopy of trees). They are also common on [[mulch]] or even in the leaf mold in gutters.  
 
The common name slime mold traces to the part of their life cycle in which their appearance can be gelatinous (hence the name slime). However, this fact mostly refers to the myxomycetes, which are the only macroscopic slime molds. They have been found all over the world feeding on microorganisms that live in any type of dead plant material. For this reason, it is very common to find these organisms growing in the soil, on lawns, and in the forest commonly on deciduous logs (hence the name [[molds]]). However, in tropical areas of the world, they also seem to be very common on [[inflorescences]], [[fruit|fruits]], and in aerial situations (i.e. in the canopy of trees). They are also common on [[mulch]] or even in the leaf mold in gutters.  
 +
 +
Most slime mold are smaller than a few centimeters, but the very largest reach areas of up to thirty square metres, making them the largest undivided cells known. Many have striking colors such as yellow, brown, and white.
 +
 +
A common slime mold which forms tiny brown tufts on rotting logs is ''[[Stemonitis]]''. Another form which lives in rotting logs and is often used in research is ''[[Physarum polycephalum]]''. In logs it has the appearance of a slimy webwork of yellow threads, up to a few feet in size. ''[[Fuligo]]'' forms yellow crusts in mulch.
  
 
==Taxonomy==
 
==Taxonomy==
Line 17: Line 21:
 
In more strict terms (''[[sensu stricto]]''), slime molds conform the group of the mycetozoans (myxomycetes, dictyostelids, and protostelids). However, even at this level there are conflicts yet to be resolved. Recent molecular evidence shows that the first two groups are likely to be monophytelic; however the protostelids seem to be polyphyletic too. For this reason, scientists are trying to elucidate the relations between these three groups.
 
In more strict terms (''[[sensu stricto]]''), slime molds conform the group of the mycetozoans (myxomycetes, dictyostelids, and protostelids). However, even at this level there are conflicts yet to be resolved. Recent molecular evidence shows that the first two groups are likely to be monophytelic; however the protostelids seem to be polyphyletic too. For this reason, scientists are trying to elucidate the relations between these three groups.
  
−
==Life cycle==
+
==Types of slime mold and life cycles==
−
They begin life as [[amoeba]]-like [[cell (biology)|cells]]. These unicellular amoebae are commonly [[haploid]] and multiply if they encounter their favorite food, [[bacteria]].  These amoebae can mate if they encounter the correct mating type and form [[zygote]]s which then grow into plasmodia which contain many [[Cell nucleus|nuclei]] without [[cell membranes]] between them, which can grow to be meters in size. One variety is often seen as a slimy yellow network in and on rotting logs. The amoebae and the plasmodia engulf microorganisms. The plasmodium grows into an interconnected network of protoplasmic strands (Ling, 1999).
+
[[Image:Haeckel Mycetozoa.jpg|thumb|right|Mycetozoa from [[Ernst Haeckel]]'s 1904 ''Kunstformen der Natur'' (Artforms of Nature)]]
 +
 
 +
Slime molds exhibit an alternation of generation life cycle, in which one phase consisting of a motile, feeding and growing animal-like phase and the other phase is an immotile, plant-like reproductive phase. This life cycle superficially resembles that of fungi and involve forming clusters of spores, sporangia, often on the tip of stalks, in the plant-like reproductive phase, when spores are released to produce new single cells and begin the life cycle again.
  
−
Within each protoplasmic strand the cytoplasmic contents rapidly stream.  If one strand is carefully watched for about 50 seconds the cytoplasm can be seen to slow, stop, and then reverse direction. The streaming protoplasm within a plasmodial strand can reach speeds of up to 1.35 mm per second which is the fastest rate recorded for any organism (Alexopoulos, 1962).  Migration of the plasmodium is accomplished when more protoplasm streams to advancing areas and protoplasm is withdrawn from rear areas. When the food supply wanes, the plasmodium will migrate to the surface of its substrate and transform into rigid '''fruiting bodies'''.  The fruiting bodies or sporangia are what we commonly see, superficially look like fungi or molds but they are not related to the true fungi. These sporangia will then release spores which hatch into amoebae to begin the life cycle again (Ling, 1999).
+
Slime molds can generally be divided into two main groups: plamodial slime molds and cellular slime molds.  
  
−
==Types of slime mold==
+
A '''plasmodial slime mold''' involves numerous individual, flagellated cells that are attached to each other, fused to form one large membrane. This "supercell" is essentially a bag of cytoplasm containing thousands of individual nuclei.
−
[[Image:Haeckel Mycetozoa.jpg|thumb|right|Mycetozoa from [[Ernst Haeckel]]'s 1904 ''Kunstformen der Natur'' (Artforms of Nature)]]
+
 
−
Most slime mold are smaller than a few centimetres, but the very largest reach areas of up to thirty square metres, making them the largest undivided cells known. Many have striking colours such as yellow, brown and white.
+
Plasmodial slime molds begin life as [[amoeba]]-like [[cell (biology)|cells]]. These unicellular amoebae are commonly [[haploid]] and multiply if they encounter their favorite food, [[bacteria]]. These amoebae can mate if they encounter the correct mating type and form [[zygote]]s, which then grow into '''plasmodia''' that contain many [[Cell nucleus|nuclei]] without [[cell membrane]]s between them. They can grow to be meters in size. One variety is often seen as a slimy yellow network in and on rotting logs. The amoebae and the plasmodia engulf microorganisms. The plasmodium grows into an interconnected network of protoplasmic strands (Ling 1999).
  
−
Slime molds can generally be divided into two main groups. A plasmodial slime mold involves numerous individual cells attached to each other, forming one large membrane. This "supercell" is essentially a bag of cytoplasm containing thousands of individual nuclei. By contrast, cellular slime molds spend most of their lives as individual unicellular protists, but when a chemical signal is secreted, they assemble into a cluster that acts as one organism.
+
Within each protoplasmic strand, the cytoplasmic contents rapidly stream. If one strand is carefully watched, the cytoplasm can be seen to slow, stop, and then reverse direction. The streaming protoplasm within a plasmodial strand can reach speeds of up to 1.35 millimeters per second, which is the fastest rate recorded for any organism (Alexopoulos, 1962).  Migration of the plasmodium is accomplished when more protoplasm streams to advancing areas and protoplasm is withdrawn from rear areas.  
  
−
A common slime mold which forms tiny brown tufts on rotting logs is ''[[Stemonitis]]''. Another form which lives in rotting logs and is often used in research is ''[[Physarum polycephalum]]''. In logs it has the appearance of a slimy webwork of yellow threads, up to a few feet in size. ''[[Fuligo]]'' forms yellow crusts in mulch.
+
When the food supply wanes, the plasmodium will migrate to the surface of its substrate and transform into rigid '''fruiting bodies'''. The fruiting bodies or sporangia are what we commonly see superficially look like fungi or molds but they are not related to the true fungi. These sporangia will then release spores, which hatch into amoebae to begin the life cycle again (Ling 1999).
  
−
The Protostelids' life cycle is very similar to the above descriptions, but they are much smaller, the fruiting bodies only forming one to a few spores.
+
A '''cellular slime mold''' involves amoeba like unicellular protists that spend most of their lives as individuals, but when a chemical signal is secreted, they assemble into a cluster that acts as one organism. Both Acrasiomycota (family Acrasidae) and Dictyostelida are cellular slime molds, although they are not considered to be closely related.  
  
−
The [[Dictyosteliida]], cellular slime molds, are distantly related to the plasmodial slime molds and have a very different life style. Their amoebae do not form huge coenocytes, and remain individual. They live in similar habitats and feed on microorganisms. When food runs out and they are ready to form sporangia, they do something radically different. They release signal molecules into their environment, by which they find each other and create swarms. These amoeba then join up into a tiny multicellular slug-like coordinated creature, which crawls to an open lit place and grows into a fruiting body. Some of the amoebae become spores to begin the next generation, but some of the amoebae sacrifice themselves to become a dead stalk, lifting the spores up into the air.
+
The [[Dictyosteliida]], cellular slime molds, are distantly related to the plasmodial slime molds but have the very different life cycle like the Acrasidae. The Dictyosteliida amoebae do not form huge coenocytes, and remain individual. They live in similar habitats and feed on microorganisms. When food runs out and they are ready to form sporangia, they do something radically different than the plasmodial slime molds. They release signal molecules into their environment, by which they find each other and create swarms. These amoeba then join up into a tiny multicellular slug-like coordinated creature, which crawls to an open lit place and grows into a fruiting body. Some of the amoebae become spores to begin the next generation, but some of the amoebae sacrifice themselves to become a dead stalk, lifting the spores up into the air.
  
 
The [[Percolozoa|Acrasidae]] have a life style similar to Dictyostelids, but their amoebae behave differently and are of uncertain taxonomic position.
 
The [[Percolozoa|Acrasidae]] have a life style similar to Dictyostelids, but their amoebae behave differently and are of uncertain taxonomic position.
 +
 +
The Protostelids' life cycle is very similar to the plasmodial life cycle, but they are much smaller, the fruiting bodies only forming one to a few spores.
  
 
The [[Plasmodiophorids]] also form coenocytes but are internal parasites of plants (e.g., [[club root]] disease of cabbages).
 
The [[Plasmodiophorids]] also form coenocytes but are internal parasites of plants (e.g., [[club root]] disease of cabbages).
  
 
Finally, the [[Labyrinthulomycetes]] are marine and form labyrinthine networks of tubes in which amoebae without [[pseudopods]] can travel.
 
Finally, the [[Labyrinthulomycetes]] are marine and form labyrinthine networks of tubes in which amoebae without [[pseudopods]] can travel.
−
 
−
==Slime molds in culture== <!-- pun intended, naturally —>
 
−
Although usually overlooked, slime molds have occasionally found their way into art and literature. Traditional [[Finland|Finnish]] lore describes how malicious [[witch]]es used yellow Fuligo (there called "paranvoi," or butter of the [[familiar]]) to spoil [[milk]].
 
−
In many popular [[roguelike]]s, as a hold-over from the original [[Rogue (computer game)|''Rogue'']], "slime mold" is the default name of a food item. Whether or not most actual slime molds are delicious, or even edible, is unclear, and some may be [[poisonous]].  However, mycologist Tom Volk reports that the plasmodium of ''[[Fuligo]]'' is eaten in [[Mexico]]. <sup>[http://botit.botany.wisc.edu/toms_fungi/june99.html]</sup> The graphic novel ''[[Nausicaä of the Valley of the Wind (manga)|Nausicaä of the Valley of Wind]]'' features a highly dangerous [[mutated]] slime mold that engulfs entire cities. [[Philip K. Dick]]'s novel [[Clans of the Alphane Moon]] contains a character called Lord Running Clam, a "Ganymedean Slime Mold" who talks and is very intelligent and has [[telepathic]] powers. In Jeffrey Darlington's comic [[General Protection Fault (comic)|General Protection Fault]], one character's poor hygiene leads to the development of a sentient species of slime mold in his apartment that split the rent with him. In the DVD release of ''[[This is Spinal Tap]]'' there is an outtake of an interview with [[David St. Hubbins]] in which he speaks of slime molds: "Slime molds are so close to being both plant and animal... that it's like they can't make up their minds... and they're thinking now that maybe it's this, is who's been running the earth all this time."
 
−
 
−
==See also==
 
−
[[Swarming motility]]
 
  
 
==References==
 
==References==

Revision as of 23:44, 14 November 2008

Slime mold from Olympic National Park, USA (Possibly Physarum)

Slime mold is the common name for any of the members of a polyphyletic grouping of heterotrophic, fungi-like amoeboid (i.e. like an amoeba) organisms that have an alternation of generations life cycle where at some point separate single-celled protists aggregate into a large swarm. There are two main forms. In plasmodial slime molds (myxomycetes), the individual flagellated cells fuse such as to make one large supercell with one large membrane surrounding numerous individual nuclei. In cellular slime molds (Acrasiomycota and Dictyostelida), the individual cells aggregate but retain their individual cell membranes. There are other groups listed as slime molds as well.

While slime molds have a life cycle that resembles that of fungi, and once were classified in that group, they now are considered unrelated to the fungi and generally are classified with the Protista.

The common name slime mold traces to the part of their life cycle in which their appearance can be gelatinous (hence the name slime). However, this fact mostly refers to the myxomycetes, which are the only macroscopic slime molds. They have been found all over the world feeding on microorganisms that live in any type of dead plant material. For this reason, it is very common to find these organisms growing in the soil, on lawns, and in the forest commonly on deciduous logs (hence the name molds). However, in tropical areas of the world, they also seem to be very common on inflorescences, fruits, and in aerial situations (i.e. in the canopy of trees). They are also common on mulch or even in the leaf mold in gutters.

Most slime mold are smaller than a few centimeters, but the very largest reach areas of up to thirty square metres, making them the largest undivided cells known. Many have striking colors such as yellow, brown, and white.

A common slime mold which forms tiny brown tufts on rotting logs is Stemonitis. Another form which lives in rotting logs and is often used in research is Physarum polycephalum. In logs it has the appearance of a slimy webwork of yellow threads, up to a few feet in size. Fuligo forms yellow crusts in mulch.

Taxonomy

Slime molds as a group (sensu lato) are polyphyletic. They were originally represented by the subkingdom Gymnomycota in the Fungi kingdom and included the defunct phyla Myxomycota, Acrasiomycota, and Labyrinthulomycota. Today, slime molds have been divided between four supergroups and paradoxically none of them is included in the Fungi. These are:

  • Mycetozoa, which includes the defunct phylum Myxomycota, belong to the supergroup Amoebozoa and include:
    • Myxogastria or myxomycetes and Protosteli: syncytial or plasmodial slime molds or protostelids.
    • Dictyosteliida: unicellular slime molds or dictyostelids.
  • Acrasiomycota: slime molds that belong to the supergroup Excavata as the family Acrasidae. They have a similar life style to Dictyostelids.
  • Labyrinthulomycota: slime nets which belong to the supergroup Chromalveolata as the class Labyrinthulomycetes.
  • Plasmodiophorids: parasitic protists that belong to the supergroup Rhizaria. They can cause cabbage club root disease and powdery scab tuber disease.

In more strict terms (sensu stricto), slime molds conform the group of the mycetozoans (myxomycetes, dictyostelids, and protostelids). However, even at this level there are conflicts yet to be resolved. Recent molecular evidence shows that the first two groups are likely to be monophytelic; however the protostelids seem to be polyphyletic too. For this reason, scientists are trying to elucidate the relations between these three groups.

Types of slime mold and life cycles

Mycetozoa from Ernst Haeckel's 1904 Kunstformen der Natur (Artforms of Nature)

Slime molds exhibit an alternation of generation life cycle, in which one phase consisting of a motile, feeding and growing animal-like phase and the other phase is an immotile, plant-like reproductive phase. This life cycle superficially resembles that of fungi and involve forming clusters of spores, sporangia, often on the tip of stalks, in the plant-like reproductive phase, when spores are released to produce new single cells and begin the life cycle again.

Slime molds can generally be divided into two main groups: plamodial slime molds and cellular slime molds.

A plasmodial slime mold involves numerous individual, flagellated cells that are attached to each other, fused to form one large membrane. This "supercell" is essentially a bag of cytoplasm containing thousands of individual nuclei.

Plasmodial slime molds begin life as amoeba-like cells. These unicellular amoebae are commonly haploid and multiply if they encounter their favorite food, bacteria. These amoebae can mate if they encounter the correct mating type and form zygotes, which then grow into plasmodia that contain many nuclei without cell membranes between them. They can grow to be meters in size. One variety is often seen as a slimy yellow network in and on rotting logs. The amoebae and the plasmodia engulf microorganisms. The plasmodium grows into an interconnected network of protoplasmic strands (Ling 1999).

Within each protoplasmic strand, the cytoplasmic contents rapidly stream. If one strand is carefully watched, the cytoplasm can be seen to slow, stop, and then reverse direction. The streaming protoplasm within a plasmodial strand can reach speeds of up to 1.35 millimeters per second, which is the fastest rate recorded for any organism (Alexopoulos, 1962). Migration of the plasmodium is accomplished when more protoplasm streams to advancing areas and protoplasm is withdrawn from rear areas.

When the food supply wanes, the plasmodium will migrate to the surface of its substrate and transform into rigid fruiting bodies. The fruiting bodies or sporangia are what we commonly see superficially look like fungi or molds but they are not related to the true fungi. These sporangia will then release spores, which hatch into amoebae to begin the life cycle again (Ling 1999).

A cellular slime mold involves amoeba like unicellular protists that spend most of their lives as individuals, but when a chemical signal is secreted, they assemble into a cluster that acts as one organism. Both Acrasiomycota (family Acrasidae) and Dictyostelida are cellular slime molds, although they are not considered to be closely related.

The Dictyosteliida, cellular slime molds, are distantly related to the plasmodial slime molds but have the very different life cycle like the Acrasidae. The Dictyosteliida amoebae do not form huge coenocytes, and remain individual. They live in similar habitats and feed on microorganisms. When food runs out and they are ready to form sporangia, they do something radically different than the plasmodial slime molds. They release signal molecules into their environment, by which they find each other and create swarms. These amoeba then join up into a tiny multicellular slug-like coordinated creature, which crawls to an open lit place and grows into a fruiting body. Some of the amoebae become spores to begin the next generation, but some of the amoebae sacrifice themselves to become a dead stalk, lifting the spores up into the air.

The Acrasidae have a life style similar to Dictyostelids, but their amoebae behave differently and are of uncertain taxonomic position.

The Protostelids' life cycle is very similar to the plasmodial life cycle, but they are much smaller, the fruiting bodies only forming one to a few spores.

The Plasmodiophorids also form coenocytes but are internal parasites of plants (e.g., club root disease of cabbages).

Finally, the Labyrinthulomycetes are marine and form labyrinthine networks of tubes in which amoebae without pseudopods can travel.

References
ISBN links support NWE through referral fees

Dog Vomit slime mold
  • Sleigh, Michael. "Protozoa and Other Protists". Routledge, Chapman and Hall Inc. 1989
  • Alexopolous, C.J., Charles W. Mims, M. Blackwell et al., Introductory Mycology, 4th ed. (John Wiley and Sons, Hoboken NJ, 2004) ISBN 0-471-52229-5
  • Martin, G.W and C. J. Alexopoulos. 1969. "The Myxomycota" Iowa University Press.
  • Ling, H. 1968. "Light and Fruiting in Didymium iridis" Mycologia Vol. pp 966-970.
  • Ling, H. 1999. "Myxomycetes, Commonly Overlooked Plants" The Native Plant Society of NJ Newsletter, Fall p5.
  • Alexopolous, C.J. 1962, second edition. "Introductory Mycology" John Wiley and Sons, p. 78.
  • Lister,A. 1925. "A Monograph of the Mycetozoa" Johnson Reprint Corp. NY.
  • Raper, K.B. (1984) The Dictyostelids. Princeton University Press.
  • Karling, J.S. (1968) The Plasmodiophorales. Hafner Publishing Co.
  • Bill Bryson's "A Short History of Nearly Everything".
  • Nick Arnold's "Nasty Nature" (a volume in the "Horrible Science" series).

External links

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

The history of this article since it was imported to New World Encyclopedia:

Note: Some restrictions may apply to use of individual images which are separately licensed.

Retrieved from https://www.newworldencyclopedia.org/p/index.php?title=Slime_mold&oldid=853245

Content is available under Creative Commons Attribution/Share-Alike License; additional terms may apply. See Terms of Use for details.
Copyright Logo
Powered by MediaWiki