Eukaryotes and viruses
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Eukaryotes and Viruses. Chapters 12 and 13. Fungi. Heterotrophic, Mainly Opportunistic Pathogens. Distinguishing Characteristics of Fungi. Chemoheterotrophic Cells walls composed of Chitin Diverse Metabolic Capabilities for Complex Carbohydrates Xerophilic Aerobic/Facultative Anaerobes

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Eukaryotes and Viruses

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Eukaryotes and Viruses

Chapters 12 and 13


Heterotrophic, Mainly Opportunistic Pathogens

Distinguishing Characteristics of Fungi

  • Chemoheterotrophic

  • Cells walls composed of Chitin

  • Diverse Metabolic Capabilities for Complex Carbohydrates

  • Xerophilic

  • Aerobic/Facultative Anaerobes

  • Prefer Low pH

Vegetative Growth

  • Filamentous Fungi

  • Yeasts

  • Dimorphic Fungi

Filamentous Fungi

  • Hyphae (individual strands)

    • Septate

    • Coenocytic

  • Mycelium (mass of hyphae)

  • Aerial Hyphae

  • Mass of Conidia


  • Bud

  • Bud Scar

  • Pseudohyphae

Dimorphic Fungi

  • Medically very important

  • Hyphae in the Environment, Yeast in the host

  • Temperature and CO2 are common triggers

Fungal Lifecycle

  • Haplodiplontic Lifecycles

  • Asexual Cycle

  • Sexual Cycle

Haplodiplontic Life Cycle














Asexual Spores

  • Genetically Identical to the parent

  • Genetically Haploid

  • Several Types

    • Conidia

    • Blastoconidia

    • Arthroconidia

    • Chlamydoconidia

    • Sporangiospores

Sexual Spores

  • Haploid Spores Arising from a Diploid Cell

  • Genetic Recombination of compatible mating types

  • Fungi are classified on the basis of their sexual cycles.

Medically Important Phyla

  • Zygomycota

  • Ascomycota

  • Basidiomycota

  • Deuteromycota (Asexual Fungi)


  • Coenocytic Hyphae

  • Not a phylogentically distinct group.

  • Sporoangiospores and Zygospores

  • Rhizopus is a common genus.


  • Septate Hyphae and Yeasts

  • Largest group of classified fungi

  • Most Deuteromycota are classified in this group by Genetics

  • Ascospores(in an ascus) and Conidia


  • Septate Hyphae

  • Basidiospores produced on Basidium, some produce conidia (though this is crude terminology)


  • Depreciated, though still used Taxon

  • Holding Phyla with no observed sexual state

  • Most have been reclassified as Ascomycota based on Genetics

  • Leads to confusion over nomenclature

    • Telomorph : Sexual State (preferred name)

    • Anamorph : Asexual State (common name)

Fungal Disease

  • Mycoses are not common but difficult to treat.

  • Mycoses are defined by the depth of tissue affected.

  • Most fungi are either superficial or opportunistic pathogens… though overt pathogens exist.

Examples of Fungal Disease


Diverse Unicellular Eukarya Pathogens


  • Phylogenetically, a diverse and ill-defined group.

  • Medically we are worried about the heterotrophs, not the photosynthetic phyla

  • Complex lifecycles with unique stages

    • Trophozoite

    • Schizogony

    • Cyst

Protists Are NOT Monophyletic


  • Lack Mitochondria, but possess relics called mitosomes.

  • Move by means of Flagella

  • Possess two nuclei.

Giardia intestinalis


  • No mitochondria

  • No microtubules

  • Obligate intra-cellular pathogens

  • Common in AIDS


  • Phylogenetically these organisms are not linked to a definite clade.

  • Movement through pseudopods


  • Named for the Apical complex, an organelle used for cell penetration.

  • Complex Lifecycles with both a definitive and intermediate host

Plasmodium species


  • Hemoflagellates, more appropriately called Kinetoplastids, are the pathogenic members.

  • Possess unique single mitochondrion called kinetoplasts.

  • Many are Parasitic


The Worms

Characteristics of Pathogens

  • They may lack a digestive system

  • They have a reduced nervous system

  • Lacking or atrophied movement systems

  • Complex reproductive systems

  • May be dioecious or monoecious


  • Flatworms, so called for overall flat body plan.

  • Actually the Subphylum Neodermata

  • All have a Neodermis (also called a cuticle) to protect them from the host and lack adaptations such as eyepores (found in free-living flatworms)


  • Flukes

  • Ventral and Oral Sucker to attach to host tissue.

  • Life Cycles involve more than a single host and mutiple developmental stages

Schistosoma Life Cycle


  • Tapeworms

  • Three body sections, scolex, neck and proglottids

  • No digestive system

  • Mature proglottids are released through feces of host.

Phylum Nematoda

  • Roundworms, due to the circular body cross-section.

  • Not to be confused with Phylum Annileda, the segmented worms (i.e. Earthworms)

  • Complete digestive systems

  • Sexually dimorphic

  • Numerous through out the environment

Comparative Anatomy

Nematoda Diseases

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