Eukaryotes and Viruses Chapters 12 and 13
Fungi Heterotrophic, Mainly Opportunistic Pathogens
Distinguishing Characteristics of Chemoheterotrophic Fungi 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 CO 2 are common triggers
Fungal Lifecycle Haplodiplontic Lifecycles Asexual Cycle Sexual Cycle
Haplodiplontic Life Cycle Gametophyte (n) Egg Haploid Spores Sperm Sporocyte Zygote Sporangia Sporophyte (2n) Embryo Diploid
Genetically Identical to the parent Genetically Haploid Several Types Conidia Blastoconidia Arthroconidia Chlamydoconidia Sporangiospores Asexual Spores
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
Viral Characteristics and Structure Why Viruses aren t Alive
General Characteristics of Viruses Name derives from the Latin for poison Obligatory intracellular parasites Referred to as filterable Contain a single type of nucleic material The nucleic material is covered in a protein coat. Use the synthesis machinery of the host to multiply.
Why are they not Alive? No independent metabolism or reproduction No single phylogenetic origin No cellular structure No ribosomes Though they DO evolve and reproduce.
Host Range Viruses have a specific subset of cell types they will infect, referred to as Host Range. Most viruses can only infect a single species Some viruses can cross species barriers Numerous factors influence host range Viruses that infect bacteria are referred to as bacteriophage or simply phage.
Viral Particle Size Poxviridae Lentiviruses Staphylococcus Bacteria 1 μm in diameter Picornaviridae Bacteriophage
Viral Structure A Virion is a complete, infectious viral particle and is composed of Nucleic Acid Capsid and Envelope
Nucleic Acid Only a single type of nucleic acid (RNA or DNA) is present in any species of virus. Unlike cellular life, viral nucleic acid can be either single or double-stranded (again only a single type per species) Size of the genetic structure can range from a few thousand base pairs to a quarter of a million
Capsid and Envelope Capsids are regular repeating protein structures composed of capsomeres. Some viral species also have a host-derived envelope surrounding the capsid Some viral species have protein/ carbohydrate spikes rising from the surface that can be used for identification
Viral Morphology
Viral Taxonomy How do you do a taxonomy of something that isn t alive?
Viral Taxonomy Without a shared phylogeny there is no use for the higher taxons (Domain, Kingdom, Phylum, and Class) Typically viral species are referred to by Order, Family, Genus and a descriptive common name (in place of a species epithet) Based on Nucleic Acid type Strategy of replication Morphology Host range
Viral Replication No, not 1 becomes 2, more like 1 becomes 1000.
Growing Bacteriophage
Growing Animal Viruses
Viral Identification Polyphasic Identification Morphology Detection of Antibodies Western Blotting of known viral proteins Nucleic Methodologies PCR RFLP RNA PCR
Lytic Bacteriophage Cycle Attachment Release Penetration Biosynthesis Maturation
Lysogenic Bacteriophage Cycle Lytic Cycle
Animal Unenveloped DNA Viral Replication
DNA vs. RNA Viral Replication There are various types of RNA viruses. Replication of the Genetic Material can be simple or a multistep process. +RNA, direct translation and replication by viral protein -RNA, indirect translation and replication by viral protein dsrna, direct translation and relication by viral protein Retroviruses, conversion of RNA to DNA, integration and then production by host.
Comparison Bacteriophage Attachment to Cell Wall proteins. Viral DNA is injected into cell No removal of capsid required Biosynthesis in cytoplasm Lysogeny Host cell lysed for release Animal Attachment to plasma membrane proteins and glycoproteins. Capsid enters cells Capsid removed by enzymes Biosynthesis in nucleus or cytoplasm Latency Enveloped viruses bud and nonenveloped rupture.
Viruses and Cancer One of many factors
Oncogenic Viruses Some viruses and known to help trigger cancers, called oncogenic viruses. These viruses affect oncogenes, natural parts of our genetic structure that can cause cancer. The process of becoming cancerous is termed transformation. Oncogenic Viruses integrate into the host genetic material.
Known Oncogenic Viruses Type of Virus Viral Species Associated Cancer DNA Human Papillomavirus Cervical Cancer Epstein-Barr Virus Hepatitis B Virus Kaposi Sarcoma-Associated Hepervirus Merkel Cell Polyomavirus Burkitt s Lymphoma Liver Cancer Kaposi Sarcoma Merkel Cell Carcinoma RNA Human T-Lymphotropic Virus 1 Leukemia Hepatitis C Virus Liver Cancer
Latency, Persistence and the Prions
Acute, Latent, and Persistent Viral Infections Acute Infections are those that cause immediate proliferation. Latent infections can occur by itself or after an acute infection, where the viral load remains undetected for a long period of time before reemerging quickly. Persistent Infections are ones where the viral load build over a long period of time.
Graph of Acute, Latent and Persistent Viral Infections
Prions Prions are infectious protein particles Prions are altered forms of a normal protein in the host that can catalyze the alteration of other normal protein particles to the prion state They cause neurological degradation and death with no known treatment. Since each prion protein is infectious, they are extremely resistant to control measures.
Prion Reaction PrP C + PrP Sc 2 PrP Sc