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• 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

Yeast

• 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

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.

Medically Important Phyla

• Zygomycota

• Ascomycota

• Basidiomycota

• Deuteromycota (Asexual Fungi)

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.

Examples of Fungal Disease

Protozoa

Diverse Unicellular Eukarya Pathogens

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

Protists Are NOT Monophyletic

Archaezoa

• Lack Mitochondria, but possess relics called mitosomes.

• Move by means of Flagella

• Possess two nuclei.

Giardia intestinalis

Microspora

• No mitochondria • No microtubules• Obligate intra-

cellular pathogens

• Common in AIDS

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

Plasmodium species

Eugelnozoa

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

• Possess unique single mitochondrion called kinetoplasts.

• Many are Parasitic

Helminths

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

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

Schistosoma Life Cycle

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

Comparative Anatomy

Nematoda Diseases