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
Haploid
Gametophyte
(n)
Spores
Egg
Sperm
Zygote
Sporocyte
Sporangia
Sporophyte
(2n)
Embryo
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 intracellular 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