slime mold

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slime mold


slime fungus,

a heterotrophic organism once regarded as a fungus but later classified with the ProtistaProtista
or Protoctista
, in the five-kingdom system of classification, a kingdom comprising a variety of unicellular and some simple multinuclear and multicellular eukaryotic organisms.
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. In a recent system of classification based on analysis of nucleic acid (genetic material) sequences, slime molds have been classified in a major group called the eukarya (or eukaryoteseukaryote
, a cell or organism composed of cells that have a membrane-bound nucleus and organelles (mitochondria, chloroplasts; see cell, in biology) and genetic material organized in chromosomes in which the DNA is combined with histone proteins.
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), which includes plants and animals. There are two groups of slime molds, the plasmodial slime molds of the phylum (division) Myxomycota and the cellular slime molds of Acrasiomycota.

Slime molds have complex life cycles that may be divided into an animallike motile phase, in which growth and feeding occur, and a plantlike, immotile, reproductive phase. The motile phase is commonly found under rotting logs and damp leaves, where cellulose is abundant. It consists in the cellular slime molds of solitary, amebalike cells, and in the Myxomycota of a coenocytic (multinucleate) mass of protoplasm called a plasmodium, which creeps about by ameboid movement. Plasmodia often grow to a diameter of several inches and are frequently brightly colored. Both types ingest solid food particles using a process called phagocytosis (see endocytosisendocytosis
, in biology, process by which substances are taken into the cell. When the cell membrane comes into contact with a suitable food, a portion of the cell cytoplasm surges forward to meet and surround the material and a depression forms within the cell wall.
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). They feed on living microorganisms, such as bacteria and yeasts, as well as decaying vegetation. Before entering the reproductive stage, a plasmodium moves to a drier, better-lit place, such as the top of a log. In the amebalike, or cellular, slime molds, up to 125,000 individual cells aggregate and flow together, forming a multicellular mass called a pseudoplasmodium that resembles a slug and crawls about before settling in a location with acceptable warmth and brightness.

In the reproductive stage the plasmodium or pseudoplasmodium is transformed into one or more reproductive structures called fruiting bodies, each consisting of a stalk topped by a spore-producing capsule that resembles the reproductive structures of many fungi. Eventually the cellulose-walled spores are released and dispersed; they germinate in wet places, releasing naked cells. In a typical plasmodial slime mold the germinated spores go through an ameboid or flagellated swimming stage, followed by sexual fusions and cell divisions. The diploid ameboid cell (i.e., the zygote) grows and its nucleus divides repeatedly, resulting in the formation of a new plasmodium. Under adverse conditions a plasmodium may be transformed into a hard, dry, inactive mass called a sclerotium. Resistant to desiccation, it becomes a plasmodium again when favorable conditions return.

In the case of the cellular slime molds, each spore released becomes a single ameba, which feeds individually until starving cells release a chemical signal that causes them to aggregate into a new pseudoplasmodium, and the process is repeated. In sexual reproduction two haploid amebas fuse, then engulf surrounding amebas, forming a single organism called a macrocyst. The macrocyst then undergoes meiosis and mitosis and releases haploid individuals.

There are about 65 cellular and 500 known plasmodial slime mold species, found in forests and sometimes lawns throughout the world. In a few species the plasmodium, under favorable conditions, may cover an area of several square feet. A slime mold is the cause of clubrootclubroot,
disease of cabbages, turnips, radishes, and other plants belonging to the family Cruciferae (or Brassicaceae; mustard family). It is induced by a plasmodial slime mold that attacks the roots, causing, in the cabbage, undeveloped heads or a failure to head at all.
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, a disease of cabbage and related plants.


See J. T. Bonner, The Cellular Slime Molds (2d ed. 1985).

slime mold

[′slīm ‚mōld]
The common name for members of the Myxomycetes. Also known as slime fungus.
References in periodicals archive ?
Nakagaki, "Smart behavior of true slime mold in a labyrinth," Research in Microbiology, vol.
Scatter a bunch of politicians in a big park in the proximity of a news camera and you'll really see slime mold at work!
Mealtime: The slime mold arrives at the oat flake and chows down.
Students should be able to replicate Nakagaki et al.'s (2000) results, demonstrating that slime mold will connect the shortest distance between two oats (Figures 1 and 2 show student results of two maze experiments).
Whether in Lee and Segal's slime mold aggregations, Bassler's bacteria, Gordon's ant colonies, or Galton's uneducated fairgoers, the absence of a single entity commanding group behavior is remarkable--and it is this very lack that makes emergence both so alluring and so counterintuitive, even unsettling.
They watched the slime mold self-organize, spread out, and form a network that was comparable in efficiency, reliability, and cost to the real-world infrastructure of Tokyo's train network.
For Johnson, Keller's slime mold has become one model for the still-diffuse sciences of complexity, which study systems that have many interacting parts.
We now not only understand the ways of slime mold, we can simulate them; and beyond that, we can harvest the results.
We repackaged the program with jazzy names (Water Detectives; Fun in the Dark; The Exciting World of Slime Mold); and we promoted the program with Broadwayesque musical spiels.
Evolutionary trees, branching diagrams that often look like a cross between a candelabra and a subway map, aren't just for figuring out whether aardvarks are more closely related to moles or manatees, or pinpointing a slime mold's closest cousins.
Hauser, "Plasmodial vein networks of the slime mold Physarum polycephalum form regular graphs," Physical Review E, vol.
Dictyostelium discoideum, aka a slime mold, is the latest member in a small club of species known to practice farming.