AMOEBAE

SOIL MICROBIOLOGY


BIOL/CSES 4684


This webpage was created by Christina Capuano

1. IDENTIFYING CHARACTERISTICS  The above picture shows Amoeba proteus, approximately 30 microns wide, seen using Laser Scanning Confocal Microscopy.


2. TAXONOMIC DESCRIPTION
The name amoeba refers to members of the genus Amoeba as well as other Protozoa with pseudopodia.  Most amoebae lack any flagellate stage, although some eventually have a transient flagellate phase.  The majority of these microorganisms are uninucleate and many produce resting cysts rather then spores or fruiting bodies.  They have no fixed shape, reproduce by binary fission, and use a psuedopod, or "false foot" to move.  This is done by extending the psuedopod from the body and using that to drag itself.  The pseudopod also helps the microbe to take in food.  The typical ameoba is basically an envelope that contains protoplasm and a nucleus.  The protoplasm consists of a cytoplasm, granular endoplasm, and ectoplasm.

Amoebae are very difficult to identify unless in motion because one species can look very different in various states of activity.  Thus, taxonomists use certain traits to identify species.  These include: size, shape, dimension, form, surface, color, use of pseudopodia, etc.  Other ways include: enzymatic distinctions, immunological differences, metal-ion contents, and cytoplasmic transplantation tolerance.
 
 
The above picture shows a Vorticella, a ciliated Protozoan.  This is an example of the type of prey large amoebae attack.


3. ISOLATION AND ECOLOGY
Amoebae are very abundant in nature and geographically diverse.  They are commonly found in both fresh water and salt water, but can also be found in soil and as parasites in humans and other invertebrates.  The aquatic environments can range from muddy bottoms of stagnant ponds and streams for the Pelomyxa palustris species to plant and algal associations of shallow, sunlit, quiet waters for Dinamoeba mirabilis and M. dofleini.

Complete isolation of amoebae is very difficult because, as with other protozoa, organisms of other species are generally present as food sources.  There is no single medium that is suitable for all amoebae; the medium changes with the species as each species preys on different organisms and the medium must be able to support both the amoebae and its prey.  The one constant for the medium is that it must have a liquid base, but can vary from a saline solution to liquid media to agar media.  Amoeba have no nerves, but can react to stimulation such as strong light, touch and very warm or very cold temperatures.  They respond to this by either moving away from the offending stimuli, or rolling into a ball.  Retreating into itself is also how they are able to survive in unfavorable conditions such as dry spells.  The amoeba will curl up into a ball and excrete most of its water.  It will then form a protective layer around itself, called a cyst membrane, and remain like that until conditions improve.  Only then will it unroll itself.
 
The above picture shows what a typical Amoeba looks like.


4. ADDITIONAL SOURCES OF INFORMATION
Baker, J.R. and Kreier, J.P. Parasitic Protozoa. Boston: Allen and Unwin, 1987.
Baker, John R. and Kreier, Julius P. Parasitic Protozoa. 2nd ed. New York: Academic Press
    Inc., 1993.
Jeon, Kwang W., ed. The Biology of Amoeba. New York: Academic Press, 1973.
Madigan, Michael T., Martinko, John M., and Parker, Jack. Biology of Microorganisms. New
    Jersey: Prentice Hall, 2000.
Martinez, A. Julio. Free-living Amebas: Natural History, Prevention, Diagnosis, Pathology, and
    Treatment of Disease. Florida: CRC Press, Inc., 1985.
Page, F.C. Freshwater and Soil Amoebae. Freshwater Biological Association. Scientific Publication
    No. 34.

5. LINKS TO OTHER SITES ON Amoebae

 Microbe Zoo This site has pages for numerous microbes including some interesting information on Amoebae.

 Dennis Kunkel's Microscopy This site contains numerous pictures of various microbes.

 Planet Amoeba  This site has general information on Amoebae as well as some pictures.

 Compton's Encyclopedia Online Contains basic information on Amoebae.
 

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