SLIME MOULDS

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Slime moulds are eukaryotic organisms that have fungus-like features as well as some animal- or protists-like features. They are ubiquitously found in the soil, dead plant matter, rotting wood, lawns and forest floors. Slime moulds were previously classified as fungi because of some characteristics which both organisms share. Slime moulds like fungi produce spores and fruiting bodies known as hyphae. These features warranted there earlier classification as fungi but this is no longer the case. Slime moulds are motile organisms, and they exhibit some amoebic-like features in locomotion. Slime moulds are made up of two main divisions which are the Myxomycota (Myxomycetes) andthe Acrasiomycota (Acrasiomycetes).

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Myxomycetes are the acellular slime moulds. They can also be called plasmodial slime moulds. Acellular (plasmodial) slime moulds are ubiquitously found in leaves, rotten woods and other moist environments as amoebic structures.  The vegetative forms of plasmodial slime moulds in the environment exist as growing single mass of protoplasm.

The mass of protoplasm in slime moulds contain numerous diploid nuclei, and they are generally known as plasmodium (plural: plasmodia) because they lack cell walls. Following nutrient depletion or scarcity of water in their natural environment, the plasmodium form fruiting bodies which later develops into resistant spores that later re-germinate when environmental conditions becomes favourable again. Plasmodial slime moulds move by cytoplasmic streaming, and their amoeboid movement helps them to absorb nutrient from the environment. Physarum species is a typical example of acellular or plasmodial slime moulds.

Acrasiomycetes are cellular slime moulds. The vegetative forms of cellular slime moulds exist as single amoebae in the environment. Cellular slime moulds have haploid nuclei, and they have independent cells unlike acellular slime moulds that have a mass of protoplasm. Cellular slime moulds unlike the acellular types feed on other microorganisms such as bacteria and yeast which they ingest through the process of phagocytosis. They form spores during unfavourable environmental conditions but re-germinate into their original amoebic form when normal conditions returns.

Further reading

Anaissie E.J, McGinnis M.R, Pfaller M.A (2009). Clinical Mycology. 2nd ed. Philadelphia, PA: Churchill Livingstone Elsevier. London.

Baumgardner D.J (2012). Soil-related bacterial and fungal infections. J Am Board Fam Med, 25:734-744.

Calderone R.A and Cihlar R.L (eds). Fungal Pathogenesis: Principles and Clinical Applications. New York: Marcel Dekker; 2002.

Champoux J.J, Neidhardt F.C, Drew W.L and Plorde J.J (2004). Sherris Medical Microbiology: An Introduction to Infectious Diseases. 4th edition. McGraw Hill Companies Inc, USA.       

Gladwin M and Trattler B (2006). Clinical Microbiology Made Ridiculously Simple. 3rd edition. MedMaster, Inc., Miami, USA.

Larone D.H (2011). Medically Important Fungi: A Guide to Identification. Fifth edition. American Society of Microbiology Press, USA.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of Microorganisms, 12th edition. Pearson Benjamin Cummings Inc, USA.

Stephenson S.L (2010). The Kingdom Fungi: The Biology of Mushrooms, Molds and Lichens. First edition. Timber Press.

Sullivan D.J and Moran G.P (2014). Human Pathogenic Fungi: Molecular Biology and Pathogenic Mechanisms. Second edition. American Society of Microbiology Press, USA.

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