MA

Protozoa/Protozoan Notes

Protozoa/Protozoan

  • Eukaryotes, like human cells.
  • Treatments can have greater side effects due to similarity to human cells.

General Terms

  • Mode of Transmission: How the organism spreads from host to host. Describes how an organism spreads from host to host (important for the exam).
  • Host: An organism infected with a pathogen that develops symptoms and can spread it.
  • Reservoir: A lower-level organism (compared to humans) that indirectly transmits the pathogen, often without developing symptoms. Transmits through stool or something of that nature.
  • Vector: Often an insect, a lower-level organism that directly transmits the pathogen, usually by a bite.

Examples:

  • Yersinia pestis (Bubonic Plague):

    • Rats: Reservoir
    • Fleas: Vector
    • Humans: Host (cutaneous, bubonic, or pneumonic plague)

  • Ticks are arachnids (eight legs) that transmit diseases like Lyme disease.

  • Mild winters increase insect populations, including ticks.

  • Lyme disease can be treated aggressively, especially early in the infection.

  • Lyme disease can remain dormant for a long period and then start causing disease.

General Characteristics (Kingdom Protista/Protozoa)

  • All single-celled organisms.
  • Eukaryotes (cells structured like ours).
  • Lack chlorophyll; cannot undergo photosynthesis.
  • Free-living in marine, freshwater, or terrestrial environments.
  • Require high moisture levels.
  • Some species are parasites, gaining energy from a host while causing harm.

Structure and Reproduction

  • Lack a rigid cell wall; may have a flexible cell wall.
  • Shape is determined by the rigidity/flexibility of the cytoskeleton.
  • Complex reproductive life cycles, often requiring a host.

Cell Shapes

  • Cyst:
    • Resting form produced under adverse conditions. Cytoplasm becomes dormant with a hard outer coating.
    • Breaks open under favorable conditions to release a trophozoite.
  • Trophozoite:
    • Mature, vegetative form of the cell; can carry out all cellular functions, including sexual reproduction.
  • Sporozoite:
    • Immature, vegetative form; can perform all functions except sexual reproduction (only asexual).

Reproduction Types

  • No distinct genders, but have mating types (e.g., type one and two).
  • Sexual reproduction occurs if another mating type is present.
  • Asexual reproduction occurs if no other mating type is present.

Schizogony

  • Nucleus replicates multiple times inside the cell; the cytoplasm divides among the new nuclei.
  • Results in many parasites being released simultaneously within a host.
  • 1 cell can become 10-20 cells in a short time.

Classification

  • Primarily based on mode of motility.

Four Groups

  • Zooflagellates:
    • Move by flagella which are similar to bacterial flagella but not turned on and off based on the environment.
    • Flagella is used for movement.
    • The use of flagella depends on organism and life cycle.
    • Flagella can be used for moving, acting like sensory receptors and to attach to things, and food gathering.
  • Ciliates:
    • Move by cilia arranged in rows. Beat in unison to propel the organism.
    • Example: Paramecium.
    • Oral groove cilia sweep food into the cell.
  • Sarcodynes/Sarcodyna:
    • Move by pseudopodia (cytoplasm streams forward, changing the shape).
    • Example: Amoeba.
    • Cytoplasm streams in the direction of movement or food, engulfing it.
  • Sporozoa:
    • Move via cysts, spores, or sporozoites.
    • Non-motile on their own.
    • Move between hosts typically via cysts in diarrhea.