Protists

1. Protists Eukaryotic Organisms

2. Protists • Protists: Eukaryotic microorganisms in the Protist family.

3. Protists • Typically have external structures for motility. These include… • Flagella: Two central microtubules & 9 pairs of peripheral microtubules (a 9+2 arrangement) surrounded by a membrane. • Found in protozoa & algae, but only have one or two. • Cilia: Shorter & more numerous than flagella – have the same basic chemical composition & structure. • Beat together in a coordinated pattern along the surface to create a “wave”.

4. Protists • Pseudopodia: “False feet” that are temporary projections of cytoplasm associated with amoeboid movement. • Cytoplasmic Streaming: Movement that occurs along a surface via pseudopodia.

5. Classes of Protists • Protists are divided into 3 groups: • Plant-like Protists aka Algae • Fungus-like Protists • Animal-like Protists

6. Plant-Like Protists • Plant-Like Protists aka Algae: Organisms with chloroplasts & carry on photosynthesis. • Typically found in moist & sunny environments. • Most have a cell wall & one or two flagella for motility. • Most reproduce via binary fission. • Includes dinoflagellates, diatoms, & euglenoid dinoflagellates. • Not associated with human disease.

7. Fungus-Like Protists • Fungus-Like Protists: Known as oomycota. • Use sexual reproduction instead of asexual. • Spend most of their life cycle as diploid cells, which are the result of a union of two haploid gametes during sexual reproduction. • Includes water molds & slime molds. • Water molds cause agriculturally relevant diseases. • Ex. Downy mildew on grapes, late blight on potatoes, etc. • Slime molds cause mildew & are sometimes classified as fungi. • NEITHER type cause disease in humans! • Saprophytes: Class that receives nutrients by decomposing dead organisms – slime molds fall into this category!

8. Animal-Like Protists • Animal-Like Protists aka Protozoa: Mostly unicellular organisms, possibly found in colonies. • Most are free living • Many live in watery environments • Can encyst (close itself in a cyst) to preserve genetic material in unfavorable conditions. • Commensalism: The process of living in or on other organisms without harming them. • Protists can do this! • Parasitism: The process of living in or on another organism while taking nutrients from that organism – may or may not harm them. • Protists can do this too!

9. Protozoa • There are 4 main classes of Protozoa, ALL of which have members that can cause human disease… • Mastigophorans • Sarcodines • Apicomplexans • Ciliates

10. Mastigophorans • Mastigophorans: Mainly free-living, unicellular, flagellated organisms. • Some have symbiotic (helpful) relationships with plants & animals. • Some parasitize humans. • Trypanosoma:Causes African sleeping sickness. • Leishmania:Causes skin lesions or systemic disease with fever. • Giardia:Causes severe diarrhea. • Trichomonas:Causes vaginal inflammation. bb

11. Sarcodines • Sarcodines: Protozoans that move & capture food by forming pseudopodia. • Feed mainly on other microorganisms, including other protozoa & algae. • Causes Ameobic dysentery.

12. Apicomplexans • Apicomplexans: Protozoans that are parasitic. • Parasitic • Immobile • Typically have complex life cycles requiring more than one host. • Plasmodium: The parasite that causes malaria. • Toxoplasma gondii: Infects domestic cats & can be passed on through handling of feces – causes damages to the unborn fetus of a pregnant human.

13. Ciliates • Ciliates: The largest group of protozoans, categorized by their large number of cilia. • Have cilia over most of their surfaces. • Contractile Vacuole: A well-developed organelle that regulates cell fluid. • Balantidium coli: The only ciliate to cause human disease – causes dysentary.