Protists Eukaryotic Organisms

Protists  Protists: Eukaryotic microorganisms in the Protist family.

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”.

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

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

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.

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!

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!

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

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

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

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.

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.