Chapter 12: The Eukaryotes Lecture

Overview of Eukaryotic Cells

• Eukaryotic cell structure: Combination of plant and animal cells.
• Chapter focuses on eukaryotic microbes: Fungi, Protozoa, Algae, Helminths.
• Importance of distinguishing different types of eukaryotic microbes for medical treatment.

Fungi

• Role: Decomposers found primarily in soil.
• Structure: Can be unicellular (yeast) or multicellular (molds).
• Reproduction: Asexual and sexual.
• Pathogenicity: Only 0.2% pathogenic; mostly opportunistic pathogens.

Yeast

• Unicellular fungi.
• Identification requires enzyme profile analysis.

Molds

• Multicellular fungi, visible to the naked eye.
• Made of long filaments called hyphae (two types: septate and coenocytic).
• Reproductive cycle involves spore formation.

Diseases Caused by Fungi (Mycoses)

• Opportunistic Pathogens: E.g., Pneumocystis jirovecii, Candida albicans.
• Systemic Mycoses: E.g., Histoplasma capsulatum, Cryptococcus neoformans.
• Subcutaneous Mycoses: E.g., Sporothrix schenckii.
• Nosocomial Infections: E.g., Candida auris.
• Obligate Pathogens: E.g., Microsporum, Trichophyton (cause of athlete's foot, ringworm).

Algae

• Found in water or near it; autotrophic (photosynthetic).
• Can be unicellular (phytoplankton) or multicellular (seaweed).
• Do not cause direct diseases in humans, but can cause indirect harm via toxins during algal blooms.

Lichens

• Symbiotic relationship between fungi and algae.
• Can photosynthesize but do not harm trees or other structures they grow on.

Protozoa

• Unicellular eukaryotes found in water and soil.
• Can be heterotrophic or autotrophic; reproduce sexually or asexually.
• Exist in two forms: Trophozoite (active) and cyst (protective).
• Types:
  • Excavata: E.g., Giardia lamblia, Trichomonas vaginalis.
  • Euglenozoa: E.g., Hemoflagellates like Trypanosoma brucei, Trypanosoma cruzi.
  • Amoebozoa: E.g., Entamoeba histolytica.
  • Apicomplexa: E.g., Plasmodium (malaria), Toxoplasma gondii.
  • Ciliates: Generally non-pathogenic.

Helminths

• Multicellular eukaryotic organisms; primarily aquatic.
• Characteristics:
  • Heterotrophic.
  • Reproduce sexually; can be monoecious or dioecious.
• Types:
  • Trematodes (Flukes): E.g., Schistosoma.
  • Cestodes (Tapeworms): E.g., Taenia saginata.
  • Nematodes (Roundworms): E.g., Enterobius vermicularis (pinworm), Necator americanus (hookworm).

Hygiene Hypothesis

• Suggests increased hygiene in developed countries leads to higher rates of immune disorders (e.g., allergies, autoimmune diseases).
• Helminthic Therapy: Using helminth infections to treat autoimmune and allergic conditions.
• Current research exploring helminth use in disease treatment and immune system modulation.

These notes capture the main points from the lecture on eukaryotic microbes, detailing the different groups and their characteristics, pathogenicity, associated diseases, and relevance in medicine and ecology.