eukaryotes and viruses chapters 12 and 13. fungi heterotrophic, mainly opportunistic pathogens
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Distinguishing Characteristics of Fungi
• Chemoheterotrophic• Cells walls composed of Chitin• Diverse Metabolic Capabilities for
Complex Carbohydrates• Xerophilic• Aerobic/Facultative Anaerobes• Prefer Low pH
Filamentous Fungi
• Hyphae (individual strands)– Septate– Coenocytic
• Mycelium (mass of hyphae)
• Aerial Hyphae• Mass of Conidia
Dimorphic Fungi
• Medically very important
• Hyphae in the Environment, Yeast in the host
• Temperature and CO2 are common triggers
Haplodiplontic Life Cycle
Gametophyte(n)
Sporophyte(2n)
Egg
Sperm
Zygote
Embryo
Sporangia
Sporocyte
Spores
Haploid
Diploid
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.
Zygomycota
• Coenocytic Hyphae• Not a
phylogentically distinct group.
• Sporoangiospores and Zygospores
• Rhizopus is a common genus.
Ascomycota
• Septate Hyphae and Yeasts
• Largest group of classified fungi
• Most Deuteromycota are classified in this group by Genetics
• Ascospores (in an ascus) and Conidia
Basidiomycota
• Septate Hyphae• Basidiospores
produced on Basidium, some produce conidia (though this is crude terminology)
Deuteromycota
• 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.
Protozoans
• 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
Archaezoa
• Lack Mitochondria, but possess relics called mitosomes.
• Move by means of Flagella
• Possess two nuclei.
Giardia intestinalis
Amoebozoa
• Phylogenetically these organisms are not linked to a definite clade.
• Movement through pseudopods
Apicomplexa
• Named for the Apical complex, an organelle used for cell penetration.
• Complex Lifecycles with both a definitive and intermediate host
Eugelnozoa
• Hemoflagellates, more appropriately called Kinetoplastids, are the pathogenic members.
• Possess unique single mitochondrion called kinetoplasts.
• Many are Parasitic
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
Platyhelminthes
• 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)
Trematodes
• Flukes• Ventral and Oral
Sucker to attach to host tissue.
• Life Cycles involve more than a single host and mutiple developmental stages
Cestodes
• 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
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