Protozoa, Fungi, Algae, and Arthropod Vectors: Classification and Features

Protozoa: Classification and Features

Alveolates: Types and Characteristics

Alveolates are a group of protozoa characterized by the presence of alveoli—membrane-bound sacs beneath their cell membranes. The three main types of alveolates are Ciliates, Apicomplexans, and Dinoflagellates.

• Ciliates

  • Possess cilia for movement or to move water past their cell surfaces.

  • Are chemoheterotrophs with two nuclei: a macronucleus and a micronucleus.

  • Reproduce via conjugation, involving the exchange of nuclei between compatible cells.

  • Examples: Vorticella, Balantidium, Paramecium

• Apicomplexans

  • Chemoheterotrophic pathogens of animals.

  • Reproduce using schizogony (multiple fission).

  • Contain a complex of organelles at the apex of infective stages, enabling host cell penetration.

  • Examples: Plasmodium, Cryptosporidium, Toxoplasma

• Dinoflagellates

  • Unicellular microbes with photosynthetic pigments (carotene, chlorophylls a, c1, c2).

  • Can be bioluminescent or produce red pigments, causing red tide.

  • Major component of freshwater and marine plankton.

  • Covered in cellulose plates; have two flagella (one wraps around the cell, one propels forward).

  • Some produce neurotoxins.

Amoebas: Types and Features

Amoebas are protozoa that move and feed using pseudopods. Three main types are Radiolaria, Foraminifera, and Entamoeba.

• Radiolaria

  • Have ornate shells made of silica.

  • Live unattached as marine plankton.

  • Pseudopods reinforced with microtubules radiate from the central body.

• Foraminifera

  • Armored marine amoebas with porous shells.

  • Pseudopods extend from shell holes.

  • Live attached to sand grains on the ocean floor.

• Entamoeba

  • Live inside animals.

  • Can cause amebic dysentery, a potentially fatal disease.

Classification of Selected Protozoa

• Euglena (Euglenozoa)

  • Photoautotrophic, unicellular with chloroplasts (chlorophylls a, b, carotene).

• Giardia (Diplomonadida)

  • Pathogen causing diarrhea; spread via cysts in contaminated water.

  • Has two nuclei and many flagella.

• Trypanosoma (Kinetoplastids/Euglenozoa)

  • Live inside animals; some are pathogenic.

  • Single large mitochondrion with kinetoplast (unique mitochondrial DNA region).

  • Causes African sleeping sickness.

• Trichomonas (Parabasala)

  • Lives in the human vagina; proliferation causes inflammation and potential sterility when pH rises.

• Leishmania (Kinetoplastids/Euglenozoa)

  • Live inside animals; some are pathogenic.

  • Single large mitochondrion with kinetoplast.

  • Transmitted by sand fly.

Fungi: Structure and Classification

Fungal Structures: Thallus, Hyphae, Haustoria, and Mycelium

Fungi possess unique structures for growth and nutrient acquisition.

• Thallus: Vegetative body made of filaments or plates of cells; found in fungi, algae, and similar organisms.

• Hyphae: Long, branched, tubular filaments in molds.

  • Septate hyphae: Have cross walls (septa).

  • Aseptate hyphae: Lack septa.

• Haustoria: Modified hyphae that penetrate host tissues to withdraw nutrients (analogous to mosquito proboscis).

• Mycelium: Tangled mass of hyphae forming the main body of a mold; often subterranean and extensive.

• Fruiting bodies: Visible reproductive structures (e.g., mushrooms, puffballs) formed from hyphae.

Fungal Genera: Division and Features

Genus	Division	Distinguishing Features
Agaricus	Basidiomycota	Reproduces via basidiospores; edible; widely cultivated
Amanita	Basidiomycota	Reproduces via basidiospores; has septate hyphae
Cryptococcus	Basidiomycota	Does not form hyphae; forms sexual spores in basidium; causes fungal meningitis; airborne transmission
Claviceps	Ascomycota	Causes ergot on grain; leads to abortions in cattle and hallucinations in humans (Saint Anthony's fire)
Saccharomyces	Ascomycota	Ferments sugar to produce alcohol and CO2; used in baking and brewing
Penicillium	Ascomycota	Beneficial mold; source of antibiotic penicillin
Rhizopus	Zygomycota	Feeds on decaying matter; causes mucormycosis; found on fruits
Neurospora	Ascomycota	Important tool in genetics and biochemistry

Lichens

Structure and Example

A lichen is a symbiotic partnership between a fungus and a photosynthetic microbe (such as cyanobacteria or green algae). The fungus provides structure and protection, while the photosynthetic partner supplies nutrients.

• Example: Lichen formed by association of a fungus and Gelidum (a red alga).

Algae: Groups, Cell Wall Components, and Examples

Group	Common Name	Cell Wall Components	Representative Genus
Rhodophyta	Red algae	Agar or carrageenan	Gelidum
Chrysophyta/Bacillariophyceae	Diatoms	Silica; cell walls (frustules) in two halves	Stephanodiscus
Dinophyta	Dinoflagellates	No cell walls	Gymnodinium
Phaeophyta	Brown algae	Cellulose and alginic acid	Macrocystis

Arthropod Vectors: Diseases Transmitted

Vector	Disease(s) Transmitted
Fleas	Plague
Lice	Typhus
True flies	Leishmaniasis, Sleeping sickness
Mosquitoes	Malaria, Yellow fever, Dengue fever, Filariasis, Viral encephalitis, Rift Valley fever
Kissing bugs	Chagas' disease