Microbiology Procedure

Index >> Microorganisms Types >> Protozoa

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Microorganism Types Plantae and Animalia Protists Eukaryotes and Prokaryotes Primary Subdivisions of Cellular Organisms Monera Main Groups of Microorganisms Bacteria Actinomycetes Protozoa Algae Fungi Viruses Microbial Classification Approaches Artificial Approach Natural Approach

Protozoa

	Protozoa - They are commonly defined as unicellular, eukaryotic animals. To a microbiologist, however, it is not a very helpful definition. It would perhaps be more appropriate to say that they are a group of unicellular non photosynthetic, eukaryotic microorganisms which normally obtain their food by phagocytosis and which possess no true cell wall. They are involved in many blood and tissue diseases. The movement is an important aspect in life cycle. A few of their characteristics are as follows: (I) The type of movement, used to divide protozoa into major groups: (a) Amoeboid motion as in Amoeba and similar forms.
(b) Flagellar movement as in flagellate protozoa, some of which are the colourless counterparts of particular algae. Some as trypanosomes (cause of sleeping sickness) have simple flagellum, while others as in Trichonympha (an organism inhabiting the guts of termites where it is responsible for the wood cellulose eaten by insect) there is very complex flagellar arrangement. (c) Ciliary movement in ciliates, as in Paramecium, whose surface covered with cilia, that are shorter than flagella and have a co-ordinated motion so that waves of contraction pass over them.
(2) Food, taken by phagocytosis of solid particles such as bacteria. (3)They have generally no cell wall. (4)Life cycles less complicated than algae or fungi, exceptions being forms like Plasmodium. (5) Degree of specialisation in single cells, as in Paramecium. Some authors also study slime molds and water molds alongwith protozoa, thus prefer to treat them protists rather than fungi. They have been traditionally studied by mycologists.
However, evidence is accumulating to show that phylogenetically they are protists. The slime molds form like fungi, macroscopic fruit bodies. But their feeding phase is amoeboid. They live on surface of decaying vegetation. There are two main groups: (a) the cellular slime molds, whose vegetative stage is single amoeboid cells that may aggregate to form a pseudoplasmodium as in Dictyostelium, and
	(b) acellular slime molds, where a single amoeba produces a multinucleate plasmodium of indefinite size and shape which moves over the surface of the substratum engulfing food particles as it goes. The water molds are of two main types, the oomycetes and the chytrids, originally included among the fungal kingdom. They are shown phylogenetically protists, most obviously because they form flagellated motile cells. However, their nutritional processes and vegetative states appear more like fungi than protists.

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Phylogenetic Approach Adansonian Approach - Numerical Taxonomy Macromolecular Approach DNA Base Composition DNA Base Compositions of Representative Bacteria Constancy of G+C content in Strains of Bacteria Nucleic Acid Hybridization Classification of Bacteria from Bergey's Manual of Determinative Bacteriology

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