Introduction to Eukaryotes in Microbiology

Overview of eukaryotic organisms important to microbiology.
Discussion includes fungi, protozoa, helminths, algae, and lichen (considered a superorganism).

Definition: Fungi are classified as chemoheterotrophs, obtaining energy and carbon from organic matter.
Types of Fungi:
- Yeasts: Single-celled fungi.
- Molds: Multicellular fungi.
- Dimorphic Fungi: Exhibit characteristics of both yeasts and molds.
Physical Characteristics of Fungi:
- All fungi have cell walls made of chitin, a polysaccharide that provides rigidity and structure.

Composed of multicellular filaments called hyphae.
- Hyphae Types:
  - Septate Hyphae: Contain cell walls that separate cells.
  - Coenocytic Hyphae: Lacking septa, resulting in continuous cytoplasmic mass.
Growth Mechanism:
- Hyphae grow at the tip and can regenerate if broken (asexual reproduction).
Hyphae Components:
- Vegetative Hyphae: Embedded in organic matter, extracting nutrients.
- Aerial Hyphae: Extend above the medium; responsible for spore formation.
- Formation seen as a mycelium, a mass of hyphae visible to the naked eye (e.g., mold on bread).
Reproductive Mechanisms:
- Fragmentation: Asexually, where broken pieces develop into new colonies.
- Sporulation: Aerial hyphae produce spores, which may be asexual or undergo sexual recombination through spore fusion.

Definition: Single-celled, non-filamentous fungi.
Reproduction Process:
- Primarily via budding, where a daughter cell forms through an outgrowth of a parent cell's nucleus.
- The cell wall forms, and the daughter cell eventually separates, leaving a scar.

Capable of existing as either yeasts or molds depending on environmental conditions (temperature, CO2 concentration).
Many pathogenic fungi exhibit dimorphic characteristics, altering between forms depending on whether they are in a host or environmental settings.

Definition: Single-celled, diverse eukaryotes.
Nutrition: Heterotrophic, consuming organic material for energy and carbon.
Most protozoa are non-pathogenic; however, several are parasitic to humans and other hosts.

Symbiosis: Close association between organisms, categorized into three types:
- Mutualism: Both organisms benefit (e.g., E. coli in human intestines producing Vitamin K).
- Commensalism: One benefits while the other remains unaffected (e.g., Demodex mites in hair follicles).
- Parasitism: One benefits at the expense of the other (e.g., Giardia intestinalis causing diarrheal disease in humans).

Complex life cycles, often involving multiple hosts:
- Definitive Host: Where the parasite reaches maturity and reproduces sexually.
- Intermediate Host: Where the parasite undergoes development but does not reproduce.
Example: Entamoeba histolytica, causing amoebic dysentery; forms resistant cysts for survival in adverse conditions.

Amoeba: Moves using pseudopodia (false feet). Some can cause diseases such as amoebic dysentery and meningoencephalitis.
Paramecium: Unicellular ciliates used for propulsion and feeding; not pathogenic to humans, used in studies.
Giardia: The most common intestinal protozoan parasite in water sources, causing gastrointestinal distress.
Trypanosoma: Blood parasite causing African sleeping sickness and Chagas disease, transmitted by insect bites.

Definition: Multicellular organisms considered animals; possess complex life cycles.
Reproduction:
- Can be dioecious (separate male and female organisms) or monoecious (both male and female reproductive parts in the same organism).
Types of Helminths:
- Flatworms (e.g., flukes, tapeworms): Lack a complete digestive system, absorb nutrients from hosts.
  - Example: Clonorchis sinensis (liver fluke) is monoecious.
- Roundworms: Have a complete digestive system, many are abundant in various environments.
  - Example: Ascaris lumbricoides, affecting over 1 billion people; hookworm, infecting >500 million.