1. 25
The Protists
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2. The Protists Eukaryotes with the taxonomic classification in flux
Kingdom Protista (out dated?) is artificial grouping of over 65,000 different single-celled life forms
A polyphyletic collection of organisms
Most are unicellular
Lack the level of tissue organization present in higher eukaryotes

3. Distribution of Protists
Grow in a wide variety of moist habitats
Most are free living
Chemoorganoheterotrophic forms play role in recycling nitrogen and phosphorus
Terrestrial and planktonic forms
Photolithoautotrophic forms usually referred to as algae
Parasitic forms cause disease in humans and domesticated animals

5. Nutrition in Protists Protozoa are chemoorganoheterotrophic protists
saprophytes – nutrients obtained from dead organic matter through enzymatic degradation
osmotrophy – absorb soluble products
holozoic nutrition – solid nutrients acquired by phagocytosis
Photolithoautotrophic protists
strict aerobes, use photosystems I and II for oxygenic photosynthesis
Mixotrophic protists
use organic and inorganic carbon compounds

6. Protist Morphology
Plasma membrane structure similar to multicellular plants/animals
Pellicle structure provides support in protozoa
Cell wall in algae
Motility
Pseudopodia in amoeboids
Flagella
Cilia
Some with no motility

7. Encystment and Excystment
protists simplify in structure and become dormant (cyst) with a cell wall and very low metabolic activity
protects against environmental changes
can assist in nuclear reorganization/reproduction (schizogony and plasmotomy)
serve as a means of host to host transfer for parasitic species

8. Encystment and Excystment
A return to favorable conditions may stimulate a cyst form to return to its original state
In parasitic protists, this may occur following ingestion of a cyst by a new host organism
Giardia

9. Protist Reproductive Cells and Structures
Protists have asexual and sexual reproduction
Asexual stage usually binary fission but can be schizogony or plasmotomy
Sexual stages use fusion of gametes in syngamy process
within a single org (autogamy) or between (conjugation)

10. Protists Taxonomy
Difficult to define due to vast differences in protists
Very much in flux and an area of active research
New classification scheme is based on that of the International Society of Protistologists
doesn’t utilize hierarchical ranks (class and order)
6 Super Groups

11. Super-Group Excavata Giardia – causes diarrhea
Trichonympha – symbiotic with termites
Trichomonas vaginalis – common STD
Trypanosoma gambiense – African Sleeping Sickness
Trypanosoma cruzii – Chaga's Disease
Euglena – autotroph and heterotroph
Super-Group Excavata

12. Trichonympha Obligate mutuals of wood-eating insects such as termites
Release cellulose for digesting
May account for 1/3 biomass in termite

13. Leishmaniasis Caused by Leishmania flagellated protists
Leishmania donovani, L. tropica, L mexicana
Transmitted by sandflies when they take a blood meal
animal reservoirs include canines and rodents, also blood transfusions, needles
Three forms of infection
mucocutaneous, cutaneous, and visceral

14. Leishmaniasis Diagnosis Treatment, prevention, and control
observation of parasites within infected macrophages, cultural and serological tests
Treatment, prevention, and control
antiparasite therapy
vector and reservoir control, and epidemiological surveillance

15. Cutaneous Leishmaniasis
Lesions of mouth, nose, throat, and skin that cause extensive scarring and disfigurement
Papules that develop into crustated ulcers
Healing occurs with scarring, permanent immunity
Disease has destroyed the nasal septum and deformed the nose and lips.

17. Trichomonas vaginalis
trichomoniasis sexually transmitted infection in humans
7 million cases in U.S.
180 million worldwide

18. Trichomoniasis Caused by protist flagellate Trichomonas vaginalis
Common sexually transmitted disease
Clinical manifestations
accumulation of leukocytes at site of infection
in females, yellow purulent vaginal discharge/itching
in males, usually asymptomatic or burning urination
Diagnosis
observation of parasite in vaginal
discharge, semen, or urine
Treatment, prevention, and control
antiparasite therapy

19. Trypanosomiasis Caused by trypanosomes
group of flagellated protists
changes its protein coat (antigens) and evades the immunologic response
Transmitted by tsetse flies (African trypanosomiasis) or kissing bug (Chagas’ disease)
reservoirs include domestic cattle and other animals
Diagnosed by observation of motile parasites in blood or antibody levels

20. Trypanosomes Antigenic variation
thick glycoprotien layer coating cell wall surface which is changeable
enables the parasite’s escape from the host immune system
no vaccines
new drugs may target flagellar proteins important for division

21. African Trypanosomiasis
Clinical manifestations
interstitial inflammation and necrosis within lymph nodes and small blood vessels of brain and heart, leading to lethargy (hence name, sleeping sickness) and death within 1 to 3 years
Drug therapy is available
Vaccines not useful due to antigenic variation

24. Chagas’ Disease
Triatome ("Kissing") bug takes blood meal, defecates in wound
Trypanosome in feces is
scratched into body
Acute disease
rapid onset, trypanosome moves
through bloodstream, enters cells,
becomes amastigote, replicates
may be cleared or develop chronic form
treatment may be effective at this stage

25. Chagas’ Disease Chronic disease
amastigotes reach heart, gastrointestinal and other cells
replicate causing heart disease and other disorders due to destruction of parasitized cells in the liver, spleen, lymph nodes, GI, and central nervous system
Leading cause of heart disease worldwide and previlence is increasing in the U.S.
Only investigational treatment currently available at chronic stage
vaccines not effective due to antigenic variation of trypanosome

27. Giardiasis Caused by Giardia intestinalis
forms cysts and trophozoites
trophozoites attach to intestinal
epithelium and interfere with
nutrient absorption
Transmission usually by cyst-contaminated water
numerous animal reservoirs
asymptomatic human carriers are common
more serious disease in children

28. Giardiasis Clinical manifestations Diagnosis
acute giardiasis - severe diarrhea, epigastric pain, cramps, voluminous flatulence, and anorexia
chronic gastritis - intermittent diarrhea with periodic appearance and remission of symptoms
Diagnosis
observation of cysts or trophozoites in stools, and ELISA
Treatment, prevention, and control
antiprotozoal agents
avoiding contaminated water and use of slow sand filters in processing of drinking water

30. Euglena Commonly found in fresh water
1/3 photoautotrophic, rest are chemoorganotrophs
Euglena is the representative phototroph
pellicle - proteinaceous strips, microtubules
red eye spot (stigma) orients to light
chlorophylls a and b, carotenoids
contractile vacuole and flagella

31. Super-Group Amoebozoa
Entamoeba histolytica
causes amoebic dysentery
third leading cause of parasitic death worldwide
acquired by consuming E. histolytica cysts
may migrate to lungs, brain, liver, or skin
Naegleria fowleri
Acanthamoeba
Slime Molds (previously classified as fungi)

32. Amebiasis (Amebic Dysentery)
Caused by Entamoeba histolytica
Infection by ingestion of mature cysts from fecally contaminated water, food or hands, or from fecal exposure during sexual contact
Clinical manifestations
asymptomatic to fulminating dysentery, exhaustive diarrhea, appendicitis, and abscesses of liver, lungs, and brain

33. Amebiasis Diagnosis Treatment, prevention, and control
observation of trophozoites in fresh warm stools or cysts in ordinary stools, and serological tests
Treatment, prevention, and control
antiprotozoal agents
avoiding contaminated water and food and hyperchlorination or iodination of water supplies to destroy waterborne cysts

35. Amebic Meningoencephalitis and Keratitis
Caused by the free-living amoebae Naegleria and Acanthamoeba
facultative (opportunistic) parasites
Clinical manifestations
primary amebic meningoencephalitis
Granulomatous amoebic encephalitis
keratitis – progressive ulceration of the cornea
Diagnosis
demonstration of amoebae in clinical specimens
Treatment, prevention, and control
no drug therapy available
do not use water for contact lens care

36. Super-Group Amoebozoa continued:
Acellular and Cellular Slime Molds

37. Super-Group Rhizaria Radiolaria
Most have internal skeleton made of siliceous material

38. Foraminifera Called forams ~20mm – several centimeter size range
Filopodia are arranged in branching network (reticulopodia)
May harbor endosymbiotic algae
contribute to foram nutrition
Have characteristics tests arranged in multiple chambers that are sequentially added as organism grows

39. More about Forams Complex life cycle
sexual and asexual reproduction
Found in marine and estuarine habitats
Foram tests make up most modern-day chalk, limestone, and marble

40. Supergroup Chromoaveolata
A diverse group including autotrophic, mixotrophic, and heterotrophic protists
Some of the most significant parasitic protists
Examples:
Dinoflagellata (dinoflagellates)
Balantidium coli causes diarrhea and dysentery
Plasmodium species cause Malaria
Toxoplasma gondii causes Toxoplasmosis
Cryptosporidium parvum causes diarrheal disease
Diatoms - found in marine plankton
produce 40% to 50% of organic carbon in ocean
golden and brown algae (seaweeds and kelp)

41. Dinoflagellates Large group found in marine plankton
cause phosphorescence/toxic blooms in seawater
Nutritionally complex
Symbiotic forms
live in association with reef building corals

42. Arthropod Borne Diseases
Malaria
caused by four species of Plasmodium
transmitted by bite of an infected female mosquito
life cycle of plasmodial protists
sporozoite injected with mosquito bite
replicates as merozoite in hepatic cells
released, enters erythrocytes and replicates
lyses erythrocytes – correlates with fever

45. Malaria Clinical manifestations periodic attacks of chills and fever
anemia can result and the spleen and liver often hypertrophy
can cause cerebral malaria in children and nonimmune individuals

46. Malaria Diagnosis Treatment, prevention, and control
demonstration of parasites within Wright- or Giemsa- stained red blood cells and serological tests
Treatment, prevention, and control
antimalarial drugs
resistance has been observed
chemoprophylaxis for travelers to endemic areas
prevention via netting/insecticide to control mosquitoes
new vaccine shows promise

48. Toxoplasmosis Worldwide very common disease caused by
Toxoplasma gondii
apicomplexan (nonmotile) protist
most are asymptomatic
reservoir wild rodents, birds, small mammals
Fecal-oral transmission from infected animals
also by ingestion of undercooked meat, congenital transfer, blood transfusion, or tissue transplant

49. Toxoplasmosis Clinical manifestations diagnosis
usually asymptomatic or resembles mononucleosis
encephalitis can be fatal in immunocompromised hosts
tachyzoites cross the placenta and infect fetus, causing serious congenital defects or death
diagnosis
serological tests
treatment, prevention, and control
antiparasite therapy
minimizing exposure by: avoidance of raw meat, washing hands after soil work, cat-handling practices

50. Cryptosporidiosis Emerging disease caused by Cryptosporidium parvum
forms cysts, sporozoites, and merozoites
sporozoites parasitize intestinal epithelial cells
Transmitted from animal reservoirs in contaminated food or water
many birds and mammals shed oocysts in feces

51. Cryptosporidiosis Clinical manifestations Diagnosis
diarrhea, abdominal pain, nausea, fever, and fatigue
usually self-limiting
can be fatal in late stage AIDS patients and other immunocompromised individuals
Diagnosis
microscopic examination of stools
Treatment, prevention, and control
symptomatic/supportive therapy
cysts very resistant to chlorine

52. Diatoms Chlorophylls and accessory pigments
Frustule – two-piece cell wall of silica
unique, beautiful patterns
Important in global carbon cycling
marine planktonic diatoms produce 40–50% of organic ocean carbon
Diatomaceous Earth – significant economic algae

53. Supergroup Archaeplastida
All higher plants and many algal species are included
Chlorophytya (green algae)
Phototrophs have chlorophylls a/b and carotenoids
Many have cellulose cell walls
Exhibit a diverse morphology