In-Depth Notes on Microscopic Eukaryotes and Their Importance

Microscopic Eukaryotes

• Types of Microscopic Eukaryotes:
  • Algae: Simple autotrophs that perform photosynthesis.
  • Fungi: Heterotrophic organisms that contain chitin in their cell walls.
  • Protozoa: Unicellular heterotrophs not classified as fungi.
  • Protists: Eukaryotic microorganisms that exclude fungi, plants, and animals.
  • Multicellular Organisms:
  • Arthropods: Can transmit diseases.
  • Worms: Involved in diseases affecting humans.
  • Carried in microscopic forms.

Eukaryotic Cell Characteristics

• Differences from Prokaryotes:
  • Presence of a nucleus and membrane-bound organelles.
  • Absence of peptidoglycan in the cell wall.
  • Usually a well-developed cytoskeleton.
  • Complexity in life cycles (haploid and diploid stages).
• Reproduction:
  • Asexual reproduction occurs via mitosis.
  • Sexual reproduction occurs via meiosis, leading to gametes and the formation of diploid zygotes.

Symbiotic Relationships of Fungi

• Lichens: Association of a fungus with a photosynthetic partner.

  • The fungus absorbs water and minerals, while the photosynthetic component provides organic nutrients.
  • Key survival in extreme habitats (e.g., tundra, bare rock) and indicators of air quality.

• Mycorrhizas: Mutual associations between fungi and plant roots.

  • Increasing plant nutrient and water absorption.
  • Fungi decompose organic material to provide nitrogen and phosphorus to plants.
  • 80% of vascular plants have this relationship.

• Insect Dependence on Fungi:

  • Some insects, like leaf-cutter ants, cultivate fungi for food, digesting plant material through fungal processes.

Economic Importance of Fungi

• Production of antimicrobial medicines (e.g. penicillin).
• Genetically engineered yeasts for human proteins (e.g. insulin).
• Used in brewing and baking; important in cheese production.
• Major spoilers of food; significant economic losses from plant diseases (e.g., Dutch elm disease).

Medically Important Fungal Diseases

• Few fungi infect humans, but significant ones include:
  • Candidial Infections (Candida albicans)
  • Coccidioidomycosis (Coccidioides immitis)
  • Histoplasmosis (Histoplasma capsulatum)
  • Pneumocystis pneumonia (Pneumocystis jirovecii).
• Human illnesses can arise from:
  • Hypersensitivity reactions (e.g. allergies).
  • Infections (mycosis).
  • Intoxications (toxins).

Algae

• Characteristics of Algae:
  • Simple photosynthetic eukaryotes, differ from plants by lacking a vascular system and complex structures.
  • Can be aquatic, ranging from microscopic to macroscopic forms.
• Diversity:
  • Groups categorized by habitat, pigments, storage products, and cell wall composition.
  • Example: Brown algae have fucoxanthin and alginic acid; Red algae produce agar.

Medical Importance of Algae

• Algae can indirectly cause human disease through toxins.
• Examples:
  • Red Tides: Caused by dinoflagellates like Gonyaulax, producing neurotoxins that can poison shellfish and humans.

Protozoa

• Definition: Unicellular, animal-like heterotrophic organisms not classified as fungi or molds.
• Historically classified by locomotion (e.g. flagella, cilia, pseudopodia).

Medical Importance of Protozoa

• Vast majority do not cause disease, but significant pathogens include:
  • Malaria (Plasmodium spp.)
  • Amebiasis (Entamoeba histolytica)
  • Giardiasis (Giardia lamblia).

Helminths (Multicellular Parasites)

• Types: Renowned for roundworms (nematodes) and flatworms (cestodes and trematodes).
• Life Cycle: Can include multiple hosts.
• Transmission Methods:
  • Soil contamination, ingestion of undercooked meat, insect bites, etc.

Common Nematode Diseases

• Examples:
  • Ascariasis (Ascaris lumbricoides): Intestinal blockage and pain.
  • Hookworm: Anemia and weakness.
  • Trichinellosis: Symptoms from undercooked pork consumption.

Arthropods

• Arthropods can act as mechanical or biological vectors for diseases.
• Effective vector control is crucial in managing infectious diseases like malaria (transmitted by mosquitoes) and plague (associated with rodents).