1. Pathogenic eukaryotes: protozoa
Protozoa = unicellular eukaryotes
• Inhabit water and soil
• Members of kingdom protista
• Have nuclei and complex organelles
• Can’t be classified as fungi, animalia, or plantae

2. Protozoa: types of motility
Three main types of protozoa:
Amoeboid protozoa
• move by a gliding motion produced by
lobe-like pseudopods extending from
the cell
Ciliates
• Hair-like cilia whose vibrating motion
moves the ciliate through water
Flagellates
• one or more whip-like flagella that they
use to propel themselves through the
water

3. Protozoa: Nutrition
Chemoheterotrophic = need organic compounds (carbs,
fats, proteins) from environment
• instead of producing it themselves from sunlight or
inorganic compounds
• Some transport food across the plasma membrane
Pellicle = protective coating on some protozoa
• Requires special structures to take in food
Cytostome = mouth-like opening used
by ciliates; wave their cilia to move
food toward it

4. • Amoebas engulf food by
surrounding it with
pseudopods and
phagocytizing it
Protozoa: Nutrition
Pictured: Amoeba protozoan
feeding on a paramecium

5. Protozoa: Nutrition
Vacuoles = membrane-enclosed
compartments where digestion
takes place
• Waste is eliminated through
plasma membrane or an anal
pore
Pictured: paramecium (a ciliate
protozoa)
• Contain remnants of meal:
some euglenoid
(chlorophyll-containing)
protozoa

6. Two-stage life cycle:
Trophozite = feeding and growing stage; eats bacteria
and small particulate nutrients
Cyst = a protective capsule that permits the protozoa to
survive under unfavorable conditions
• Can live outside a host
• Must be excreted from a host to get into a new
host
Protozoa: life cycle

7. Beneficial Protozoa
• Nearly 20,000 protozoan species
• Very few causing human diseases
Ex) Nosema locustae
• Phylum Microspora
• Used as insecticide to kill grasshoppers,
crickets
• Will not affect humans or animals; only
pathogenic to certain insects

8. Phylum Archaezoa
• Many live as parasites in the digestive tract of animals
• Lack mitochondria
• Mitosome = remnant of an ancestral mitochondria
• Most have two or more flagella
Ex) Giardia lamblia
• Small intestine  Giardiasis
• Trophozite: eight flagella
• Excreted in feces as cysts
• Cysts ingested by new host
Giardia cyst

9. Ex) Trichomonas vaginalis
• Human parasite causing trichomoniasis
• Undulating membrane bordered by flagellum
• No cyst stage – must be transmitted from host to host
quickly before dessication occurs
Phylum Archaezoa
Transmission =
sexually transmitted
Symptoms =
inflammation,
burning, itching

10. Phylum Amoebozoa
Entamoeba histolytica
• Amoebic dysentery (amoebiasis)
• Only pathogenic amoeba in human intestine
• Transmission = ingestion of fecal cysts
• Lectins = proteins used to attach to plasma membranes
• Can cause lesions in intestinal wall  enter blood stream and
end up in liver  abscesses
• Move by extending pseudopods
• Food vacuoles = created when
pseudopods surround food, bring
it into the cell
E. Histolytica
trophozoite with
pseudopod

11. Phylum Apicomplexa
• Obligate intracellular parasites
• Have complexes at the apex (tip) of their cells
• contain enzymes to penetrate host tissues
• Motile structures (flagella, pseudopods) only present in
the gamete stages
• Complex life cycle
• Transmission between several hosts:
Definitive host = harbors the sexually reproducing
stage of the protozoa
Intermediate host = harbors the asexual
reproduction stage

12. Phylum Apicomplexa
Plasmodium: malaria
• Reproduce sexually in the Anopheles mosquito
Sporozoites = infective stage plasmodium transferred to
human through Anopheles bite
• Undergo schizogony in liver  merozoites
• Infect RBCs  rupture; release more merozoites
• asexual reproductive cycle continues
• Some develop into sexual forms
(gametocytes)
• Can be picked up by another
mosquito  infect new host

13. Phylum Apicomplexa
Malaria continued
Symptoms
• Fever, chills in 36-48 hour cycles caused by waste
released upon rupture of red blood cells
• Hemorraging caused by blockage of blood vessels
• Infected RBCs display adhesive proteins to avoid
destruction by spleen
Prevention
• Vaccine development is difficult due to complex life
cycle of Plasmodium
• Prevention of Anopheles bite
• Mefloquine, chloroquine, atovacuone/proguanil:
preventive when visiting malaria prone regions

14. Cryptosporidium parvum (Cyptosporidosis)
• Transmitted by ingestion of oocysts
• Animal feces, contaminated lakes & rivers
• Lives within cells of small intestine
Phylum Apicomplexa
Symptoms =
Cholera-like
diarrhea for 10-
14 days
Left: Crytpo SEM

15. Phylum Ciliophora
The ciliates: cilia are similar in structure to flagella
• Arranged in precise rows, move in unison
Ex) Balantidium coli
• Only ciliate human parasite
• Severe dysentery
Transmission = ingestion of fecal cysts
• cysts release trophozoites into large intestine  destroy
host cells by secreting proteases
• Feed on cell and tissue fragments
• Propel through environment
• Push food to the cytostome

16. Phylum Euglenozoa
Euglenoids = not parasitic; one of two Euglenozoa classes
• Photoautotrophs: use chloroplasts for photosynthesis
• Red anterior eyespot
• organelle containing pigmented carotenoids
• senses light to direct the cell towards it
• Anterior flagellum
• Facultative
chemoheterotrophs = ingest
organic matter through their
cytostome in the absence of
light

17. Phylum Euglenozoa
Hemoflagellates = blood parasites
• Transmitted by blood-feeding insect bites
• Long-slender shapes and undulating membranes
Trypanosoma: Trypanosomiasis
• aka African sleeping sickness
• Tsetse fly vector
• Parasite enters blood and
lymphatic system  transported to
other sites
• Eventually crosses blood-brain
barrier
Trypanosoma brucei SEM

18. Phylum Euglenozoa
Symptoms
• Fever, headaches, joint pain, lymph swelling
• Tryptophol = chemical produced by trypanosoma
that induces sleep
• Deterioration of CNS
Prevention = elimination of tsetse fly
• release of radiation-sterilized males
• vaccination difficult (antigenic variation)
Treatment = eflornithine; blocks enzyme
required for proliferation

19. Phylum Euglenozoa
Visceral (Leishmania donovani)
• invasion of internal organs like liver, spleen, kidneys
- Fatal without treatment
Cutaneous (Leishmania tropica)
• skin lesions
Mucocutaneous (Leishmania braziliensis)
• disfiguring destruction of nasal and oral mucosa
Leishmania: Leishmaniasis
• Tropical and mediterranean
climates
• Sandfly vector
Macrophage infected with
Leishmania donovani