Eukaryotic Microbes: Pathogenic Fungi, Arthropod Vectors, Protozoa, and Helminths (Labs 31-34)

Lab 31: Pathogenic Fungi

Fungi: Beneficial Roles

Fungi are eukaryotic organisms with diverse ecological and medical significance. They play essential roles in decomposition, food production, metabolic activities, and antibiotic synthesis.

• Decomposers: Break down dead organic matter and recycle nutrients in soil (mutualistic relationships).

• Food: Edible fungi include mushrooms and truffles.

• Metabolic Activities: Fermentation processes produce bread, wine, and beer.

• Antibiotics: Fungi such as Penicillium produce antibiotics like penicillin and cephalosporin.

Characteristics of Fungi

Fungi possess unique structural and metabolic features that distinguish them from other microorganisms.

• Eukaryotic: Cells contain a true nucleus and organelles.

• Cell Wall: Composed of chitin.

• Respiration: Aerobic respiration and fermentation.

• Nutrition: Absorptive chemoheterotrophs (obtain nutrients by absorption).

• Ecological Roles: Saprophytic (decomposers) or parasitic.

• Morphological Classification:

  • Molds

  • Macromfungi

  • Yeast

Candida

Candida species are opportunistic pathogens causing various infections, especially in immunocompromised individuals.

• Diseases:

  • Thrush (oral candidiasis)

  • Vulvovaginitis

  • Skin infections

Penicillium

Penicillium is notable for its role in antibiotic production and as a cause of seasonal allergies.

• Antibiotic Production: Source of penicillin.

• Allergies: Can trigger seasonal allergic reactions.

Trichophyton

Trichophyton species are dermatophytes that infect keratinized tissues.

• Keratinaise: Enzyme allowing colonization of skin, hair, and nails.

• Illnesses:

  • Ringworm

  • Jock itch

  • Athlete's foot

  • Onychomycosis (nail infection)

Rhizopus

Rhizopus is known as black bread mold and can cause serious infections in immunocompromised hosts.

• Sexual Spores: Zygospores

• Asexual Spores: Sporangiospores

• Disease: Mucormycosis (in immunocompromised individuals)

Lab 32: Arthropod Vectors

Overview of Arthropod Vectors

Arthropods are invertebrates that can transmit infectious agents (viruses, bacteria, protozoa) to humans, acting as vectors for disease.

Arthropod	Transmitted Disease
Culex (mosquito)	Arthropod-borne viral encephalitis
Anopheles (mosquito)	Malaria (Plasmodium spp.)
Ixodes (tick)	Lyme Disease (Borrelia burgdorferi)
Amblyomma (tick)	Ehrlichiosis (Ehrlichia spp.)
Xenopsylla (flea)	Bubonic plague (Yersinia pestis)
Pediculus (louse)	Epidemic typhus (Rickettsia prowazekii)

Lab 33: Protozoa

Diplomonads

Diplomonads are flagellated protozoa lacking typical mitochondria and Golgi apparatus, instead possessing mitosomes.

• Multiple flagella

• Example: Giardia lamblia (causes giardiasis)

Parabasalids

Parabasalids are protozoa with modified mitochondria (hydrogenosomes) and a parabasal body.

• Multiple flagella

• Axostyle: Supporting structure

• Example: Trichomonas vaginalis (causes trichomoniasis)

Kinetoplastids

Kinetoplastids possess a single large mitochondrion containing a kinetoplast (DNA-containing granule). They include important blood parasites.

• Hemoflagellates: Blood parasites

• Examples:

  • Trypanosoma brucei (African sleeping sickness)

  • Trypanosoma cruzi (American trypanosomiasis)

  • Leishmania (leishmaniasis)

Apicomplexans

Apicomplexans are obligate intracellular protozoa characterized by an apical complex and asexual reproduction via schizogony.

• Intracellular lifestyle

• Apical complex: Specialized organelles for host cell invasion

• Schizogony: Multiple fission asexual reproduction

• Example: Plasmodium (malaria)

Amoebozoan

Amoebozoans move by pseudopods and include pathogenic species causing intestinal and extraintestinal disease.

• Example: Entamoeba

  • Amoebiasis

  • Amoebic dysentery

  • Invasive amoebiasis (abscesses)

  • Secondary amebic meningoencephalitis

Lab 34: Helminths

Trematodes (Flukes)

Trematodes are leaf-shaped flatworms with bilateral symmetry and hermaphroditic reproductive systems.

• Examples:

  • Fasciola hepatica (liver fluke; causes fascioliasis)

  • Schistosoma mansoni (blood fluke; causes schistosomiasis)

Cestodes (Tapeworms)

Cestodes are segmented, hermaphroditic flatworms with a narrow, elongated body.

• Examples:

  • Taenia (beef and pork tapeworms; taeniasis)

  • Diphyllobothrium latum (fish tapeworm; diphyllobothriasis)

Nematodes (Roundworms)

Nematodes are unsegmented, cylindrical worms with bilateral symmetry and a complete digestive system. They may be dimorphic.

• Examples:

  • Enterobius vermicularis (pinworm; enterobiasis)

  • Ancylostoma duodenale (hookworm; ancylostomiasis)

  • Ascaris lumbricoides (roundworm; ascariasis)

  • Trichinella spiralis (trichinellosis)

Summary Table: Major Eukaryotic Pathogens and Diseases

Group	Example Organism	Disease
Fungi	Candida	Thrush, vulvovaginitis, skin infections
Fungi	Trichophyton	Ringworm, athlete's foot, nail infection
Fungi	Rhizopus	Mucormycosis
Protozoa	Giardia lamblia	Giardiasis
Protozoa	Trichomonas vaginalis	Trichomoniasis
Protozoa	Trypanosoma	Sleeping sickness, Chagas disease
Protozoa	Leishmania	Leishmaniasis
Protozoa	Plasmodium	Malaria
Protozoa	Entamoeba	Amoebiasis, dysentery
Helminths	Fasciola hepatica	Fascioliasis
Helminths	Schistosoma mansoni	Schistosomiasis
Helminths	Taenia	Taeniasis
Helminths	Diphyllobothrium latum	Diphyllobothriasis
Helminths	Enterobius vermicularis	Enterobiasis
Helminths	Ancylostoma duodenale	Ancylostomiasis
Helminths	Ascaris lumbricoides	Ascariasis
Helminths	Trichinella spiralis	Trichinellosis

Additional info: These notes cover the structure, classification, and medical importance of eukaryotic microbes and vectors, relevant to Microbiology chapters on cell structure, classification, infectious diseases, and epidemiology.