Myxogastria

Myxogastria
Diderma testaceum
Scientific classification
Kingdom:	Amoebozoa
Phylum:	Mycetozoa
Class:	Myxogastria
Orders
Echinosteliales Liceales Physarales Stemonitales Trichiida

Myxogastria is a class of Mycetozoa.^[1][2] The class contains 5 orders, 14 families, 62 genera, and 888 species.^[3]

It includes the genus Stemonitis.

They are also referred to as "myxogastrids".^[4]

Myxomycota

The group formerly known as "Myxomycota", now known not to be fungal, is now usually classified under Myxogastria.

An example is Physarum polycephalum.^[5]

These heterotrophic organisms are predators of microbial food webs, and so they are able to engulf and digest bacteria, yeast, fungal spores, and decaying matter^[6]

Terminology and classification

The Latin name comes from the Greek Myxo, that means "slime", and mycota, that means fungus. They are colloquially known as plasmodial or acellular slime molds or within the scientific community as myxomycetes, however the latter term does not refer to a taxonomic class. Some would also consider Myxomycota as a higher systematic group (i.e. kingdom) unto itself, with an unsettled phylogeny because of conflicting molecular and developmental data. The relations between lower systematic groups (in this case orders) are as yet unclear.^[7]

Life cycle

When a Myxomycete spore germinates, it cracks, releasing an amoeboid cell called a myxamoeba. Depending upon environmental conditions, the myxamoeba can produce flagella, in which case it is known as a swarm cell. This process is reversible and the flagellum can be retracted so the myxamoeba is established again. The latter ingests food via phagocytosis and divides as it eats. When two myxamoebae of different mating strains (of different populations) find each other, they will merge, forming a zygote. The zygote itself will not divide, but rather it will grow as its nucleus divides, forming a large, multinucleate cell called a plasmodium. The plasmodium will continue to consume organic matter through phagocytosis. After some time, for unknown causes, the plasmodium will convert into a spore-bearing structure called a fruiting body. The four major types of fruiting bodies are the sporangium, the aethalium, the psedoaethalium and the plasmodiocarp. Spores are released from the fruiting body and the life cycle starts over.

References

1. ^ "www.ncbi.nlm.nih.gov". http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=33680. Retrieved 2009-03-27. 
2. ^ Fiore-Donno AM, Berney C, Pawlowski J, Baldauf SL (2005). "higher-order phylogeny of plasmodial slime molds (Myxogastria) based on elongation factor 1-A and small subunit rRNA gene sequences". J. Eukaryot. Microbiol. 52 (3): 201–10. doi:10.1111/j.1550-7408.2005.00032.x. PMID 15926995. 
3. ^ Kirk PM, Cannon PF, Minter DW, Stalpers JA. (2008). Dictionary of the Fungi. 10th ed. Wallingford: CABI. p. 765. ISBN 0-85199-826-7. 
4. ^ Baldauf SL, Doolittle WF (October 1997). "Origin and evolution of the slime molds (Mycetozoa)". Proc. Natl. Acad. Sci. U.S.A. 94 (22): 12007–12. doi:10.1073/pnas.94.22.12007. PMC 23686. PMID 9342353. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=9342353. 
5. ^ Krishnan U, Barsamian A, Miller DL (2007). "Evolution of RNA editing sites in the mitochondrial small subunit rRNA of the Myxomycota". Meth. Enzymol. 424: 197–220. doi:10.1016/S0076-6879(07)24009-1. PMID 17662842. http://linkinghub.elsevier.com/retrieve/pii/S0076-6879(07)24009-1. 
6. ^ C.J. Alexopolous, Charles W. Mims, M. Blackwell. 1996. Introductory Mycology, 4th ed. John Wiley and Sons, Hoboken NJ.
7. ^ FIORE-DONNO Anne-Marie; BERNEY Cedric; PAWLOWSKI Jan; BALDAUF Sandra L. 2005. Higher-order phylogeny of plasmodial slime molds (myxogastria) based on elongation factor 1-A and small subunit rRNA gene sequences. The Journal of eukaryotic microbiology 52(3): 201-210.