Protozoa

• Protozoa


  Eukaryotic organisms classified in the second kingdom (Protista) of the Five Kingdom System of Classification
• Protozoan cells


  • More animal-like than plant-like
  • Possess a variety of eukaryotic structures and organelles, including cell membranes, nuclei, endoplasmic reticulum, mitochondria, Golgi bodies, lysosomes, centrioles, and food vacuoles
  • Some possess pellicles, cytostomes, contractile vacuoles, pseudopodia, cilia, and flagella
  • No chlorophyll, cannot make their own food by photosynthesis
• Pellicle


  Serves the same purpose as a cell wall, for protection
• Cytostome


  Primitive mouth or opening for ingesting food
• Contractile vacuole


  Organelle that pumps water out of the cell
• Myoneme


  Primitive muscle fiber within the contractile stalk of Vorticella spp.
• Typical protozoan life cycle

  1. Trophozoite stage (motile, feeding, dividing)

  2. Cyst stage (nonmotile, dormant, survival)
• Protozoan classification by locomotion

  • Pseudopodia
  • Flagella
  • Cilia
  • Nonmotile
• Ameboid movement


  Ameba extends a pseudopodium in the direction it intends to move, and then the rest of the cell slowly flows into it
• Phagocytosis


  Ameba ingests a food particle by surrounding it with pseudopodia, which then fuse together
• Pinocytosis


  Ameba ingests fluids in a similar manner to phagocytosis
• Medically important amebae


  • Entamoeba histolytica (causes amebic dysentery and extraintestinal abscesses)
  • Naegleria fowleri (causes primary amebic meningoencephalitis)
  • Acanthamoeba spp. (cause eye infections)
• Parasitic protozoa


  • Break down and absorb nutrients from the body of the host in which they live
  • Many are pathogens, causing diseases like malaria, giardiasis, African sleeping sickness, and amebic dysentery
  • Some have a mutualistic symbiotic relationship with the host, where both organisms benefit
• Ciliates


  • Move about by means of large numbers of hairlike cilia on their surfaces, exhibiting an oarlike motion
  • The most complex of all protozoa
• Pathogenic ciliate


  • Balantidium coli (causes dysentery in underdeveloped countries, transmitted from swine feces)
• Pond water ciliates


  • Blepharisma, Didinium, Euplotes, Paramecium, Stentor, Vorticella spp.
• Flagellated protozoa or flagellates

  • Move by means of whiplike flagella, which exhibit a wavelike motion
  • Flagella are anchored by a basal body (kinetosome or kinetoplast)
• Pathogenic flagellates


  • Trypanosoma brucei subspecies gambiense (causes African sleeping sickness)
  • Trypanosoma cruzi (causes Chagas' disease)
  • Trichomonas vaginalis (causes trichomoniasis)
  • Giardia lamblia (causes giardiasis)
• Nonmotile protozoa (sporozoa)


  Protozoa lacking pseudopodia, flagella, or cilia
• Important sporozoan pathogens

  • Plasmodium spp. (cause malaria)
  • Cryptosporidium parvum (causes cryptosporidiosis in immunosuppressed patients)
  • Babesia spp. (cause babesiosis)
  • Cyclospora cayetanensis (causes cyclosporiasis)
  • Toxoplasma gondii (causes toxoplasmosis)
• Some of the white blood cells in our bodies ingest and digest meningo
• Ciliates have cilia
• Ciliates


  • Means of Movement: Cilia
  • Method of Asexual Reproduction: Transverse fission
  • Method of Sexual Reproduction: Conjugation
  • Pathogenic Representatives: Balantidium
  • Diseases: Diarrhea
• Amebae (amebas)


  • Means of Movement: Pseudopodia (false feet)
  • Method of Asexual Reproduction: Binary fission
  • Method of Sexual Reproduction: When present
  • Pathogenic Representatives: Acanthamoeba, Naegleria
  • Diseases: Keratitis, Meningitis
• Flagellates


  • Means of Movement: Flagella
  • Method of Asexual Reproduction: Binary fission
  • Method of Sexual Reproduction: Involves flagellated sex cells
  • Pathogenic Representatives: Entamoeba, Giardia, Trichomonas, Trypanosoma
  • Diseases: Diarrhea, amebiasis, sexually transmitted disease, Chagas disease
• Sporozoa


  • Means of Movement: Generally nonmotile except for certain sex cells
  • Method of Asexual Reproduction: Multiple fission
  • Method of Sexual Reproduction: Involves flagellated sex cells
  • Pathogenic Representatives: Plasmodium, Toxoplasma, Cryptosporidium, Cyclospora
  • Diseases: Malaria, Toxoplasmosis, Diarrhea
• Most protozoa are unicellular (single-celled), ranging length in from 3 to 2,000µm. Most of them are free-living organisms, found in soil and water.
• B. coli is the only ciliated protozoan that causes disease in humans. Examples of pond water ciliates are Blepharisma, Didinium, Euplotes, Paramecium, Stentor, and Vorticella spp.,