Through the eyes of a scientist, the characteristics of slime mold make it a truly beautiful
(8)
Plasmodial Slime Mold: During its vegetative, feeding but not reproductive, stage a plasmodial slime mold is a mass of cytoplasm, without a cell wall, and with numerous diploid nuclei. It is also responsible for its common name, “pretzel mold.”
Cellular Slime Mold: Where as the plasmodium is the basic vegetative unit of the plasmodial slime molds, an amoeboid cell is the vegetative unit of the cellular smile molds.
Relationship to humans
Slime mold often grows on the mulch of gardens and is unwanted by their caretakers. Since slime mold is one cell with millions of nuclei that divide simultaneously, it is used by scientist to study mitosis. (5)
Slime mold is also very interesting to scientists for cancer drug research. Slime mold can be ripped apart and grow each half of itself independently with in sync divisions and developments of the nuclei. Because of this, slime mold is very fascinating to researchers: they can have multiple samples dividing identically (1).
Habitat and niche
Both the Plasmodial Slime Mold and Cellular Slime Mold thrive in moist environments, where food is readily available. Slime mold is especially found on forest floors, where it can feed on fungus, yeast, and bacteria by breaking down decomposing vegetation. (1)
Predator avoidance
Slime mold predators include larvae and specialized beetles, who have mandibles that are shaped somewhat similar to ice cream scoops. This allows them so scoop up the slime mold. To avoid this, slime molds can crystallize into little blobs until the danger is gone. They can also do this during unfavorable weather. (7)
Nutrient acquisition
Plasmodial Slime Mold:The plasmodial form of the slime mold covers rocks, decaying logs, and other objects as it engulfs bacteria and other food items. It forms a network of strands called a plasmodium, which in this case is an example of a coenocyte: many nuclei enclosed in single plasma membrane. As it moves, the plasmodium engulfs food particles by endocytosis—mainly bacteria, yeasts, spore of fungi, and other small organisms as well as decaying animal and plant remains.
Cellular Slime Mold: Large numbers of cells called myxamoebas, which have single haploid nuclei, engulf bacteria and other food particles by endocytosis.
Reproduction and life cycle
Plasmodial Slime Mold: The plasmodium can turn to spore-bearing fruit structures. These stalked or branched structures rise from heaped masses of plasmodium. They derive their rigidity from walls that form and thicken between their nuclei. The diploid nuclei of the plasmodium divide by meiosis as the fruiting structure develops. One or more knobs, called sporangia, develop on the ends of the stalks. Within a sporangium, haploid nuclei become surrounded by walks to form spores. Eventually, as the fruiting structure dries, it sheds its spores.
The spores germinate into wall-less, haploid cells called swarm cells, which can either divide mitotically to produce more haploid swarm cells or function as gametes. Swarm cells can live as separate individual cells that move by means of flagella or pseudopods, or they can become walled and resistant resting cysts when conditions are unfavorable. When conditions improve, the cysts release swarm cells.
Two swarm cells can also fuse to form a diploid zygote, which divides by mitosis, but without a wall forming between the nuclei, and thus forms a new coenocytic plasmodium.
Cellular Slime Mold: Large number of cells called, myxamoebas reproduce through mitosis and fission. They have a very simple life cycle, consisting of swarms of independent, isolated cells, which can persist indefinitely so long as food and moisture are available.
A mass of myxamoebas, or slug, may migrate over a substrate for several hours before becoming motionless and reorganizing to construct a stalked fruiting structure. Cells at the top of the fruiting structure develop into thick-walled spores, which are eventually released. Later, when the favorable conditions are restored, the spores germinate and release myxamoebas.
This cycle from myxamoebas through slug and spores to new myxamoebas is asexual. Cellular slime molds also have a sexual cycle, in which two myxamoebas fuse. The product of this fusion develops into a spherical structure that ultimately germinates, releasing new haploid myxamoebas.
Growth and development
Plasmodial Slime Mold: It can grow almost indefinitely in its plasmodial stage as long as the food supply is adequate and other conditions, such as moisture and pH, are favorable. If conditions become unfavorable, then one of the following two things happens.
First, the plasmodium can form an irregular mass of hardened cell-like components called a sclerotuim. This resting structure rapidly becomes a plasmodium again when the favorable conditions return. Or, the plasmodium can transform itself into spore-bearing fruit structures.
Cellular Slime Mold: When conditions are unfavorable in its environment, the cellular slime molds aggregate and form fruiting structures in the same way as the Plasmodial Slime Mold do. The individual myxamoebas aggregate into a mass called a slug or pseudoplasmodium. Unlike the real or true plasmodium, this structure is not simply a giant sheet of cytoplasm with many nuclei. The individual myxamoebas retain their plasma membrane and their identity. When slime mold is cut in half, the two halves will grow separately, but the nuclei will stay in sync (1).
Integument
Plasmodial Slime Mold: The outer cytoplasm of the plasmodium, the closest to the environment, is normally less fluid than the interior cytoplasm. It therefore provides some structural rigidity.
Movement
Plasmodial Slime Mold:Plasmodial slime molds move by cytoplasmic streaming. The outer cytoplasmic region of the plasmodium becomes more fluid in places, and cytoplasm rushes into those areas, stretching the plasmodium. The streaming, then, reverses its direction every few minutes as cytoplasm rushed into a new area and drains away from an older one, moving the plasmodium over its substrate. In some cases, an entire wave of plasmodium moves across a surface, leaving behind strands. Microfilaments and a contractile protein called myxomyosin, interact to produce this streaming movement.
Sensing the environment
When food is plentiful, slime molds exist as single-celled creatures that forage for food. When they begin to starve, however, they release a chemical signal that that causes many slime molds to fuse and become a large single-celled organism with many nuclei. This allows the slime mold to move and forage more efficiently. This larger slime mold also leaves a behind a trail of slime. In the course of its foraging, slime molds will not go to areas covered in slime, recognizing it as an area that was already explored. (6)
Gas exchange
Protists have the following characteristics on their respiratory surface in order to successfully be able to remove excess carbon dioxide from their bodies: thin-walls so diffusion can happen quickly, contact with the source of oxygen, in a moist environment. These organisms use diffusion across a cellular membrane in order to accomplish any kind of gas exchange.
Waste removal
Slime mold is able to slowly move across its food, such as bacteria or protozoa, while secreting enzymes in order to digest the particles. As this process occurs the waste is excreted and the slime mold continues to move away.
Environmental physiology (temperature, water and salt regulation)
Slime molds typically grow in highly humid and relatively warm environments, in environments with plentiful nutrition such as gardens and irrigated areas, places with excess surface water (3). In order to internally regulate water, the slime mold is capable of encasing itself in a hard-walled mass when environmental conditions are too dry, called a sclerotium. The sclerotium protects the dormant cells until favorable, moist environmental conditions return (9).
Internal circulation
Circulation of Protists is accomplished through diffusion, and because they have such thin membranes, there is no need for any kind of internal system to regulate circulation.
Chemical control (i.e. endocrine system)
When living conditions are not favorable for slime mold, the cells in the body will send out signals which morph the slime mold into a single mass. When conditions are favorable again, they let out a second signal which returns the cells to normal (10).
Review Questions
1) Compare and contrast the characteristics of plasmodial and cellular slime molds.
Classification/Diagnostic characteristics
Plasmodial Slime Mold: During its vegetative, feeding but not reproductive, stage a plasmodial slime mold is a mass of cytoplasm, without a cell wall, and with numerous diploid nuclei. It is also responsible for its common name, “pretzel mold.”
Cellular Slime Mold: Where as the plasmodium is the basic vegetative unit of the plasmodial slime molds, an amoeboid cell is the vegetative unit of the cellular smile molds.
Relationship to humans
Slime mold often grows on the mulch of gardens and is unwanted by their caretakers. Since slime mold is one cell with millions of nuclei that divide simultaneously, it is used by scientist to study mitosis. (5)Slime mold is also very interesting to scientists for cancer drug research. Slime mold can be ripped apart and grow each half of itself independently with in sync divisions and developments of the nuclei. Because of this, slime mold is very fascinating to researchers: they can have multiple samples dividing identically (1).
Habitat and niche
Both the Plasmodial Slime Mold and Cellular Slime Mold thrive in moist environments, where food is readily available. Slime mold is especially found on forest floors, where it can feed on fungus, yeast, and bacteria by breaking down decomposing vegetation. (1)Predator avoidance
Slime mold predators include larvae and specialized beetles, who have mandibles that are shaped somewhat similar to ice cream scoops. This allows them so scoop up the slime mold. To avoid this, slime molds can crystallize into little blobs until the danger is gone. They can also do this during unfavorable weather. (7)Nutrient acquisition
Plasmodial Slime Mold:The plasmodial form of the slime mold covers rocks, decaying logs, and other objects as it engulfs bacteria and other food items. It forms a network of strands called a plasmodium, which in this case is an example of a coenocyte: many nuclei enclosed in single plasma membrane. As it moves, the plasmodium engulfs food particles by endocytosis—mainly bacteria, yeasts, spore of fungi, and other small organisms as well as decaying animal and plant remains.Cellular Slime Mold: Large numbers of cells called myxamoebas, which have single haploid nuclei, engulf bacteria and other food particles by endocytosis.
Reproduction and life cycle
Plasmodial Slime Mold: The plasmodium can turn to spore-bearing fruit structures. These stalked or branched structures rise from heaped masses of plasmodium. They derive their rigidity from walls that form and thicken between their nuclei. The diploid nuclei of the plasmodium divide by meiosis as the fruiting structure develops. One or more knobs, called sporangia, develop on the ends of the stalks. Within a sporangium, haploid nuclei become surrounded by walks to form spores. Eventually, as the fruiting structure dries, it sheds its spores.The spores germinate into wall-less, haploid cells called swarm cells, which can either divide mitotically to produce more haploid swarm cells or function as gametes. Swarm cells can live as separate individual cells that move by means of flagella or pseudopods, or they can become walled and resistant resting cysts when conditions are unfavorable. When conditions improve, the cysts release swarm cells.
Two swarm cells can also fuse to form a diploid zygote, which divides by mitosis, but without a wall forming between the nuclei, and thus forms a new coenocytic plasmodium.
Cellular Slime Mold: Large number of cells called, myxamoebas reproduce through mitosis and fission. They have a very simple life cycle, consisting of swarms of independent, isolated cells, which can persist indefinitely so long as food and moisture are available.
A mass of myxamoebas, or slug, may migrate over a substrate for several hours before becoming motionless and reorganizing to construct a stalked fruiting structure. Cells at the top of the fruiting structure develop into thick-walled spores, which are eventually released. Later, when the favorable conditions are restored, the spores germinate and release myxamoebas.
This cycle from myxamoebas through slug and spores to new myxamoebas is asexual. Cellular slime molds also have a sexual cycle, in which two myxamoebas fuse. The product of this fusion develops into a spherical structure that ultimately germinates, releasing new haploid myxamoebas.
Growth and development
Plasmodial Slime Mold: It can grow almost indefinitely in its plasmodial stage as long as the food supply is adequate and other conditions, such as moisture and pH, are favorable. If conditions become unfavorable, then one of the following two things happens.First, the plasmodium can form an irregular mass of hardened cell-like components called a sclerotuim. This resting structure rapidly becomes a plasmodium again when the favorable conditions return. Or, the plasmodium can transform itself into spore-bearing fruit structures.
Cellular Slime Mold: When conditions are unfavorable in its environment, the cellular slime molds aggregate and form fruiting structures in the same way as the Plasmodial Slime Mold do. The individual myxamoebas aggregate into a mass called a slug or pseudoplasmodium. Unlike the real or true plasmodium, this structure is not simply a giant sheet of cytoplasm with many nuclei. The individual myxamoebas retain their plasma membrane and their identity. When slime mold is cut in half, the two halves will grow separately, but the nuclei will stay in sync (1).
Integument
Plasmodial Slime Mold: The outer cytoplasm of the plasmodium, the closest to the environment, is normally less fluid than the interior cytoplasm. It therefore provides some structural rigidity.Movement
Plasmodial Slime Mold:Plasmodial slime molds move by cytoplasmic streaming. The outer cytoplasmic region of the plasmodium becomes more fluid in places, and cytoplasm rushes into those areas, stretching the plasmodium. The streaming, then, reverses its direction every few minutes as cytoplasm rushed into a new area and drains away from an older one, moving the plasmodium over its substrate. In some cases, an entire wave of plasmodium moves across a surface, leaving behind strands. Microfilaments and a contractile protein called myxomyosin, interact to produce this streaming movement.Sensing the environment
When food is plentiful, slime molds exist as single-celled creatures that forage for food. When they begin to starve, however, they release a chemical signal that that causes many slime molds to fuse and become a large single-celled organism with many nuclei. This allows the slime mold to move and forage more efficiently. This larger slime mold also leaves a behind a trail of slime. In the course of its foraging, slime molds will not go to areas covered in slime, recognizing it as an area that was already explored. (6)Gas exchange
Protists have the following characteristics on their respiratory surface in order to successfully be able to remove excess carbon dioxide from their bodies: thin-walls so diffusion can happen quickly, contact with the source of oxygen, in a moist environment. These organisms use diffusion across a cellular membrane in order to accomplish any kind of gas exchange.Waste removal
Slime mold is able to slowly move across its food, such as bacteria or protozoa, while secreting enzymes in order to digest the particles. As this process occurs the waste is excreted and the slime mold continues to move away.Environmental physiology (temperature, water and salt regulation)
Slime molds typically grow in highly humid and relatively warm environments, in environments with plentiful nutrition such as gardens and irrigated areas, places with excess surface water (3). In order to internally regulate water, the slime mold is capable of encasing itself in a hard-walled mass when environmental conditions are too dry, called a sclerotium. The sclerotium protects the dormant cells until favorable, moist environmental conditions return (9).Internal circulation
Circulation of Protists is accomplished through diffusion, and because they have such thin membranes, there is no need for any kind of internal system to regulate circulation.Chemical control (i.e. endocrine system)
When living conditions are not favorable for slime mold, the cells in the body will send out signals which morph the slime mold into a single mass. When conditions are favorable again, they let out a second signal which returns the cells to normal (10).Review Questions
1) Compare and contrast the characteristics of plasmodial and cellular slime molds.References:
1. http://www.pbs.org/newshour/rundown/2012/04/the-sublime-slime-mold.html2. http://www.educationalassistance.org/Physarum/EasyToGrow/Carolina%20Biological%20-%20Slime%20Mold%20Kit%20Instrux.pdf (waste removal)
3. http://plantclinic.tamu.edu/factsheets/slime-mold/
4. http://upload.wikimedia.org/wikipedia/commons/a/a6/Yellow_slime_mold.jpg
5.http://herbarium.usu.edu/fungi/FunFacts/slimemold.htm
6. http://arstechnica.com/science/2012/10/organism-without-a-brain-creates-external-memories-for-navigation/
7. http://www.smithsonianmag.com/science-nature/phenom_mar01.html?c=y&page=1
8. http://science.kqed.org/quest/2012/02/21/beautiful-slime/
9. http://herbarium.usu.edu/fungi/FunFacts/slimemold.htm
10. http://www.microbeworld.org/types-of-microbes/protista/slime-molds