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Lab 4 Objectives
The Parasitic Protozoa:
Protozoa are heterotrophic organisms, requiring complex organic
compounds for food. Belonging to the Kingdom Protista, the free-living species typically get this nourishment
from scavenging on dead plant or animal matter, or by consuming live bacteria
and algae. In contrast, parasitic forms have adapted their life cycle to
feeding off the fluids or tissues of living hosts. The following represent
some of the medically-important protozoa known to parasitize humans.
Capsular Staining
(Anthony's Method)
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Background and Purpose:
This is a special staining technique designed to emphasize
bacterial capsules that are not normally observed using conventional staining
methods. Knowing if these capsules are present or absent is important
for species identification. Clinically, capsule-forming bacteria tend to
be more virulent because this structure protects the cell from phagocytosis.
Chemically, capsules are composed of polysaccharides, glycoproteins, or
polypeptides. Since most capsules are largely water-soluble and
nonionic, simple stains will not be attracted to them. Therefore, to view
this cell structure, most capsule staining methods are designed to stain both
the cell and the background. The capsule is left unstained or lightly
stained, making it appear like a
halo around the cell .
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General Procedure:
A bacterial smear prepared from a skim milk culture is stained
with crystal violet and rinsed with a 20% solution of copper sulfate.
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Materials:
crystal violet, 20% copper sulfate,
staining rack, slide holder, disposable latex gloves,
bibulous paper
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