Dictyostelium

Source: Wikipedia, the free encyclopedia.

Dictyostelium
Dictyostelium fruiting bodies
Scientific classification Edit this classification
Domain: Eukaryota
Phylum: Amoebozoa
Class: Dictyostelia
Order: Dictyosteliida
Family:
Dictyosteliidae
Genus: Dictyostelium
Bref.
Type species
Dictyostelium mucoroides
Brefeld 1869
Synonyms
  • Heterosphondylium Traub 1977 nom. nud. non Nägeli 1862
  • Hyalostilbum Oudemans 1885
Dictyostelium aggregations on a culture plate
Dictyostelium colony in process of aggregation
Pseudoplasmodium or "slug" of a Dictyostelium
Single amoeboid cell of Dictyostelium, showing the contractile vacuole

Dictyostelium is a

microflora, and play an important role in the maintenance of balanced bacterial populations in soils.[1][2]

The genus Dictyostelium is in the

metazoans. For further detail see family Dictyostelid
.

Discovery

The cellular slime mold was formerly considered to be fungi following their discovery in 1869 by Brefeld. Although they resemble fungi in some respects, they have been included in the kingdom Protista.[4] Individual cells resemble small amoebae in their movement and feeding, and so are referred to as myxamoebae. D. discoideum is the most studied of the genus.

Traits

Most of its life, this haploid social amoeba undergoes a vegetative cycle, preying upon bacteria in the soil, and periodically dividing mitotically. When food is scarce, either the sexual cycle or the social cycle begins. Under the social cycle, amoebae aggregate in response to

cAMP
by the thousands, and form a motile slug, which moves towards light. Ultimately the slug forms a fruiting body in which about 20% of the cells die to lift the remaining cells up to a better place for sporulation and dispersal.

When starved for their bacterial food supply and exposed to dark, moist conditions,

diploid zygote.[5] Heterothallic mating has been best studied in D. discoideum and homothallic mating has been best studied in Dictyostelium mucoroides (strain DM7). In the heterothallic sexual cycle, amoebae aggregate in response to cAMP and sex pheromones, and two cells of opposite mating types fuse, and then begin consuming the other attracted cells. Before they are consumed, some of the prey cells form a cellulose wall around the entire group. When cannibalism is complete, the giant diploid cell is a hardy macrocyst which eventually undergoes recombination and meiosis,[6] and hatches hundreds of recombinants.[7][8] In D. mucoroides (DM7) homothallic mating, cells are directed towards sexual development by ethylene.[5] Scientists also found the collective cell migration could occur without the presence of cAMP oscillations at multicellular stages, and novel models have been proposed to interpret this interesting phenomenon.[9]

Social characteristics

Professor John Tyler Bonner (1920-2019) spent a lifetime researching the slime molds and created a number of fascinating films in the 1940s to show the life cycle; he mostly studied D. discoideum. In the videos, intelligence appears to be observed as the single cells, after separation, regroup into a cellular mass. The time-lapse film captivated audiences; indeed, Bonner when giving conferences stated that the film "always stole the show".[10] The video is available on YouTube.[11]

When the organisms congregate, the mass is made of genetically distinct cells. Through natural selection, it is determined which of the organisms' genetic information will be present in future generations. The conflict is evidenced by unequal representations of two genetically different clones in spores of a chimera, the reduction of functionality seen in migrating chimeras, and a differentiation inducing factor (DIF) system, akin to poison, that appears to be made of cells forcing others to cease output of genetic information.[12]

Species

Taxonomy of Dictyostelium is complicated. It has also been confused by the different forms in the life cycle stages and by the similar Polysphondylium spp. Below are some reported examples.[13]

References

  1. ^ Landolt. C. (2006) Dictyostelid Cellular Slime Molds from Caves. Journal of Cave and Karst studies v. 68 no. 1 pp. 22-26.
  2. S2CID 232092012
    .
  3. ^ "About Dictyostelium". dictybase.org.
  4. ISBN 0-521-58364-0
    .
  5. ^
    S2CID 205599638
    .
  6. ^ Macinnes MA, Francis D. Meiosis in Dictyostelium mucoroides. Nature. 1974 Sep 27;251(5473):321-4. doi: 10.1038/251321a0. PMID 4473717
  7. ^ "Dictyostelium". www.ruf.rice.edu.
  8. ^ "dictyBase Home". dictybase.org.
  9. PMID 30701199
    .
  10. ^ "The Embryo Project Encyclopedia". Archived from the original on 2012-03-14. Retrieved 2011-07-16.
  11. ^ Archived at Ghostarchive and the Wayback Machine: Princeton University (22 January 2010). "John Bonner's slime mold movies" – via YouTube.
  12. S2CID 775816
    .
  13. PMID 29367151
    .
  14. ^ Raper, K.B. (1935). "Dictyostelium discoideum, a new species of slime mold from decaying forest leaves". Journal of Agricultural Research. 50: 135–147. Archived from the original on 2017-12-08. Retrieved 2017-12-08.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Dictyostelium&oldid=1205291453"