Study Notes: Protozoa, Fungi, Algae, and Other Eukaryotic Microbes

Protozoa

General Characteristics

Protozoa are diverse, unicellular eukaryotic organisms that lack cell walls. They are found in a variety of environments and play important ecological and medical roles.

• Motility: Protozoa move using cilia, flagella, or pseudopods.

• Cell Structure: Unicellular, eukaryotic, lacking cell walls.

• Habitats: Found in soil, water, and as parasites in animals and humans.

Distribution of Protozoa

• Most protozoa are free-living and form a crucial part of the food chain.

• Some protozoa are pathogenic to animals and humans.

Morphology of Protozoa

• Some protozoa have two nuclei (macronucleus and micronucleus).

• Some have multiple mitochondria, while others lack mitochondria.

• Contractile vacuoles may be present for osmoregulation.

• Life cycle often includes a motile stage (trophozoite) and a dormant, resistant stage (cyst).

Nutrition of Protozoa

• Most are chemoheterotrophs; some are photoautotrophs.

Reproduction of Protozoa

• Asexual reproduction: binary fission, schizogony.

• Sexual reproduction: gametocytes fuse to form a zygote; ciliates reproduce via conjugation.

Classification of Protozoa

• Grouped by locomotion:

  • Sarcodina (pseudopods)

  • Mastigophora (flagella)

  • Ciliophora (cilia)

  • Sporozoa (nonmotile)

• Genetic classification places protozoa into six taxa.

Major Groups and Examples

• Diplomonadida: Have mitosomes, two nuclei, multiple flagella. Example: Giardia (causes giardiasis).

• Euglenozoa: Have characteristics of both plants and animals. Example: Euglena (photoautotrophic, with chloroplasts), kinetoplastids (Trypanosoma, Leishmania).

• Alveolates: Include ciliates (Balantidium), apicomplexans (Plasmodium, Toxoplasma), and dinoflagellates (Gymnodinium, Gonyaulax, Pfiesteria).

• Amoebozoa: Move by pseudopods. Pathogens: Naegleria, Acanthamoeba, Entamoeba.

• Slime Molds: Plasmodial and cellular types, important in lab research.

Table: Human Pathogenic Protozoa

Group	Genus/Species	Disease
Diplomonadida	Giardia	Giardiasis (diarrhea)
Parabasalid	Trichomonas vaginalis	STD
Kinetoplastid	Trypanosoma, Leishmania	Sleeping sickness, leishmaniasis
Apicomplexan	Plasmodium, Toxoplasma	Malaria, toxoplasmosis
Ciliate	Balantidium	Balantidiasis
Amoebozoa	Naegleria, Acanthamoeba, Entamoeba	Brain infection, amoebic dysentery

Fungi

General Characteristics

Fungi are eukaryotic, chemoheterotrophic organisms with cell walls made of chitin. They include molds, mushrooms, and yeasts. The study of fungi is called mycology.

Significance of Fungi

• Beneficial:

  • Decomposers

  • Help plants absorb nutrients

  • Used in food and beverage production

  • Produce antibiotics (e.g., penicillin)

  • Used as research tools

• Harmful:

  • Cause diseases (mycoses)

  • Spoil foods

Morphology of Fungi

• Molds: Multicellular, form hyphae (can be septate or aseptate). A mass of hyphae is called a mycelium.

• Yeasts: Unicellular, reproduce by budding.

• Dimorphic fungi: Can exist as yeast or mold depending on environmental conditions.

Nutrition of Fungi

• Fungi are saprobic, absorbing nutrients from decaying matter.

• Some have specialized hyphae called haustoria for absorbing nutrients from living plants/animals.

• Most are aerobic; some are facultative anaerobes.

Reproduction of Fungi

• Asexual: Budding (yeasts), spore formation (molds: sporangiospores, chlamydospores, conidiospores).

• Sexual: Fusion of + and - hyphae, leading to dikaryon formation and sexual spores.

Table: Types of Fungal Spores

Spore Type	Formation
Sporangiospores	In a sac (sporangium) at hyphal tips/sides
Chlamydospores	Thick cell wall, within hyphae
Conidiospores	At hyphal tips/sides, not in a sac

Classification of Fungi

• Zygomycota: Multinucleate molds, reproduce via zygospores. Example: Microsporidia (obligate intracellular parasites).

• Ascomycota: Molds/yeasts, produce ascospores. Includes Penicillium (antibiotic production), Claviceps (ergot, hallucinogen), Neurospora (research).

• Basidiomycota: Mushrooms, puffballs, bracket fungi. Produce basidiospores. Example: Cryptococcus neoformans (meningitis).

• Deuteromycetes: Fungi with unknown sexual stages (classification evolving).

Lichens

General Characteristics

Lichens are symbiotic partnerships between fungi and photosynthetic microbes (algae or cyanobacteria). They are found in diverse environments and are important for soil formation and as bioindicators.

• Three basic shapes: foliose (leafy), crustose (crust-like), fruticose (shrubby).

• Used as food, dyes, and in litmus paper production.

Algae

General Characteristics

Algae are eukaryotic photoautotrophs that produce gametes. They are classified by their pigments, morphology, and reproductive strategies.

Distribution of Algae

• Mostly aquatic (fresh, brackish, salt water), but also found on soil, rocks, and trees.

• Use chlorophyll and accessory pigments to absorb light.

Morphology of Algae

• Can be unicellular, colonial, or multicellular (simple structure).

Reproduction of Algae

• Unicellular: Asexual (mitosis), sexual (gametes).

• Multicellular: Fragmentation, formation of gametes, alternation of generations (haploid/diploid stages).

Classification of Algae

• Chlorophyta (Green Algae): Similar to plants, have chlorophyll a and b, store starch. Found in fresh water.

• Rhodophyta (Red Algae): Contain phycoerythrin, used for agar and carrageenan production.

• Phaeophyta (Brown Algae): Contain xanthophylls, produce alginic acid (thickener).

• Chrysophyta (Golden Algae, Diatoms): Contain chrysolaminarin, diatoms have silica cell walls, major source of oxygen.

Table: Major Algal Groups and Features

Division	Pigment	Notable Features
Chlorophyta	Chlorophyll a, b	Freshwater, plant-like
Rhodophyta	Phycoerythrin	Red algae, agar/carrageenan
Phaeophyta	Xanthophylls	Brown algae, alginic acid
Chrysophyta	Chrysolaminarin	Diatoms, silica cell walls

Water Molds

General Characteristics

Water molds are not true fungi but are more closely related to algae. They are decomposers and can cause plant diseases, such as the Great Potato Famine.

Other Eukaryotic Microbes of Microbiological Interest: Parasitic Helminths and Vectors

Helminths

• Parasitic worms (not microbes, but important in microbiology).

• Found in human body fluids and tissues.

Arthropod Vectors

• Arachnids: Ticks and mites; transmit bacterial, viral, and protozoan diseases (e.g., Lyme disease, Rocky Mountain spotted fever).

• Insects: Fleas (plague), lice (typhus), mosquitoes (malaria, yellow fever), kissing bugs (Chagas disease).

Summary Table: Key Pathogens and Diseases

Group	Genus/Species	Disease
Protozoa	Trichomonas vaginalis	STD
Protozoa	Giardia	Giardiasis (diarrhea)
Protozoa	Trypanosoma, Leishmania	Sleeping sickness, leishmaniasis
Protozoa	Balantidium	Balantidiasis
Protozoa	Plasmodium, Toxoplasma	Malaria, toxoplasmosis
Protozoa	Gymnodinium, Gonyaulax, Pfiesteria	Neurotoxins (shellfish poisoning)
Protozoa	Naegleria, Acanthamoeba, Entamoeba	Brain infection, amoebic dysentery
Fungi	Microsporidia	Immunocompromised disease
Fungi	Claviceps purpurea	Ergot poisoning, hallucinations
Fungi	Penicillium	Antibiotic production
Fungi	Cryptococcus neoformans	Meningitis
Lichens	Fungus + Alga/Cyanobacterium	Soil formation, bioindicators

Additional info: Some explanations and examples were expanded for clarity and completeness, including the summary tables and details on classification and significance.