1. Mrs. Dalia Kamal Eldien Msc in Microbiology
The Protozoa
Mrs. Dalia Kamal Eldien
Msc in Microbiology
Lecture NO (2)

2. Objectives Definition of protozoa
Identification of their normal habitat
Mode of the reproduction
Mode of nutrition
Type of locomotion organelle
Classification of protozoa (with examples to each group)

3. Introduction
The parasites that infect humans can be grouped into three large groups: protozoa, helminths, and arthropods
Helminth is the common name used for parasitic worms. These include Trematodes (flukes), Cestodes (tapeworms), and Nematodes (roundworms). Most helminth infections occur in the intestinal tract
Arthropods include arachnids such as spiders, ticks, and mites, and insects such as lice, bugs, fleas, flies, and mosquitoes. Some arthropods, such as lice, fleas, and mosquitoes are parasitic to humans; others such as flies are important as vectors in transmitting the infective stages of parasites to humans.

4. Protozoa
Protozoa are single-celled eukaryotic organisms that are larger than most bacteria .
Protozoa(Profo=first +Zoon=animal) are the most primitive among the living animals
Most species are free living, but all higher animals are infected with one or more species of protozoa
Infections range from asymptomatic to life threatening, depending on the species and strain of the parasite and the resistance of the host.

5. Structure
Protozoa are microscopic unicellular eukaryotes that have a relatively complex internal structure including the Golgi apparatus, mitochondria, lysosomes, food vacuoles and other specialized structures
But according to many zoologists, it is not correct to designate protozoans as unicellular as they are complete organisms and not loose cells moving organs.
The body construction of some protozoa's may be more complicated than some of the simple metazoa.

6. Many protozoa alternate between a free-living vegetative form known as a trophozoite and a resting form known as a cyst.
 The protozoal cyst is somewhat analogous to the bacterial spore, since it resists harsh conditions in the environment.
Many protozoal parasites are taken into the body in the cyst form.

7. Occurrence
Protozoa prefer a moist habitat found in sea water, fresh water and also in moist soil.
They are ubiquitous and are found wherever nature offers a damp surface.
Many protozoa also occur in association with other animals.
The relationship may be mutualism, commensalism or parasitism.

8. Reproduction Size and shape
Reproduce asexually as well as sexually, even though the Principal means of multiplication is by asexual method.
Asexual reproduction takes place by cell division. This is of two types with respect to the number of daughter cells formed.
In binary fission two daughter cells are formed
in multiple fission many daughter cells are formed.
Size and shape
 Protozoa vary in size and shape.
Smaller species may be the size of fungal cells
larger species may be visible to the unaided eye.

9. Nutrition Phagocytosis: means the local infolding of the cell's
Protozoa are autotrophic(organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis) or heterotrophic (cannot synthesize their own food and rely on other organisms — both plants and animals — for nutrition. )
Most species obtain large food particles by phagocytosis
Phagocytosis:  means  the local infolding of the cell's
 membrane and the protrusion of its cytoplasm around the
 fold until the material has been surrounded and engulfed by closure of the membrane and formation of a vacuole

10. Some species have specialized structures called cytostomes, or cell mouth, is a part of a cell specialized for phagocytosis
Food vacuoles are concerned with the ingestion and digestion of food.
Food is digested by the activity of the enzymes produced by lysosomes then digest the nutrients in the particle, and the products of digestion are distributed throughout the cell.
Lysosomes are formed in the region of the golgi bodies.

12. phagocytosis

13. locomotion
Many protozoal species move independently by one of three types of locomotors organelles: pseudopodia flagella, and cilia
Pseudopodia (false foot)
Are characteristic of amoebae, where the cytoplasm forms temporary projections in the direction of movement.
The pseudopodia also help in the trapping of food.

14. Amoeba with pseudopodia

15. Flagella:
Are long fibrous extensions of the cell and are permanent features of the cell.
The number of flagella per cell varies from one to many.
The flagellum has two parts - a central filament (axoneme) and a surrounding contractile sheath.
Cilia
Are fine short threads that extend from the body surface.
All cilia in a cell may be of the same length or may vary.
Cilia not only help in locomotion but also in driving the food towards the oral grove

16. Flagellated protozoa

17. Ciliated protozoa

18. The classification of protozoa
Protozoa are categorized according to their method of movements:-
Flagellates – three of the most common and medically significant include: Giardia lamblia, Trypanosome sp. and Trichomonas vaginalis
Amoeba –include the pathogenic amoeba Entamoeba and Endolimax which cause dysentery in humans
Ciliates – the only parasitic ciliate that causes disease in humans in Balantidium coli
Sporozoa (‘spore-formers’) were originally recognized not on the basis of their locomotion.

19. Giardia lamblia flagellates

20. Entamoeba histolytica

21. Balantidium .coli

22. Entamoeba histolytica Acanthamoeba species Naegleria species
The basic generally accepted practical classification of the medically important parasitic protozoa
Amoebae
Entamoeba histolytica
Acanthamoeba species
Naegleria species
Flagellates
Giardia lamblia
Trichomonas vaginalis
Trypanosoma species
Leishmania species
Ciliates
Balantidium coli
Coccidia
Blood and tissue coccidia:
Plasmodium species
Toxoplasma gondii
Intestinal coccidia:
Isospora belli
Cryptosporidium parvum
Cyclospora cayetanensis
Microsporidia
Encephalitozoon species
Enterocytozoon species