Eukaryotes and Viruses. Chapters 12 and 13

Transcription

1 Eukaryotes and Viruses Chapters 12 and 13

2 Fungi Heterotrophic, Mainly Opportunistic Pathogens

3 Distinguishing Characteristics of Chemoheterotrophic Fungi Cells walls composed of Chitin Diverse Metabolic Capabilities for Complex Carbohydrates Xerophilic Aerobic/Facultative Anaerobes Prefer Low ph

4 Vegetative Growth Filamentous Fungi Yeasts Dimorphic Fungi

5 Filamentous Fungi Hyphae (individual strands) Septate Coenocytic Mycelium (mass of hyphae) Aerial Hyphae Mass of Conidia

6 Yeast Bud Bud Scar Pseudohyphae

7 Dimorphic Fungi Medically very important Hyphae in the Environment, Yeast in the host Temperature and CO 2 are common triggers

8 Fungal Lifecycle Haplodiplontic Lifecycles Asexual Cycle Sexual Cycle

9 Haplodiplontic Life Cycle Gametophyte (n) Egg Haploid Spores Sperm Sporocyte Zygote Sporangia Sporophyte (2n) Embryo Diploid

10 Genetically Identical to the parent Genetically Haploid Several Types Conidia Blastoconidia Arthroconidia Chlamydoconidia Sporangiospores Asexual Spores

11 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.

12 Medically Important Phyla Zygomycota Ascomycota Basidiomycota Deuteromycota (Asexual Fungi)

13 Zygomycota Coenocytic Hyphae Not a phylogentically distinct group. Sporoangiospores and Zygospores Rhizopus is a common genus.

14 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

15 Basidiomycota Septate Hyphae Basidiospores produced on Basidium, some produce conidia (though this is crude terminology)

16 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)

17 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.

18 Examples of Fungal Disease

19 Protozoa Diverse Unicellular Eukarya Pathogens

20 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

21 Protists Are NOT Monophyletic

22 Archaezoa Lack Mitochondria, but possess relics called mitosomes. Move by means of Flagella Possess two nuclei. Giardia intestinalis

23 Microspora No mitochondria No microtubules Obligate intracellular pathogens Common in AIDS

24 Amoebozoa Phylogenetically these organisms are not linked to a definite clade. Movement through pseudopods

25 Apicomplexa Named for the Apical complex, an organelle used for cell penetration. Complex Lifecycles with both a definitive and intermediate host

26 Plasmodium species

27 Eugelnozoa Hemoflagellates, more appropriately called Kinetoplastids, are the pathogenic members. Possess unique single mitochondrion called kinetoplasts. Many are Parasitic

28 Helminths The Worms

29 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

30 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)

31 Trematodes Flukes Ventral and Oral Sucker to attach to host tissue. Life Cycles involve more than a single host and mutiple developmental stages

32 Schistosoma Life Cycle

33 Cestodes Tapeworms Three body sections, scolex, neck and proglottids No digestive system Mature proglottids are released through feces of host.

34 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

35 Comparative Anatomy

36 Nematoda Diseases

37 Viral Characteristics and Structure Why Viruses aren t Alive

38 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.

39 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.

40 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.

41 Viral Particle Size Poxviridae Lentiviruses Staphylococcus Bacteria 1 μm in diameter Picornaviridae Bacteriophage

42 Viral Structure A Virion is a complete, infectious viral particle and is composed of Nucleic Acid Capsid and Envelope

43 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

44 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

45 Viral Morphology

46 Viral Taxonomy How do you do a taxonomy of something that isn t alive?

47 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

48 Viral Replication No, not 1 becomes 2, more like 1 becomes 1000.

49 Growing Bacteriophage

50 Growing Animal Viruses

51 Viral Identification Polyphasic Identification Morphology Detection of Antibodies Western Blotting of known viral proteins Nucleic Methodologies PCR RFLP RNA PCR

52 Lytic Bacteriophage Cycle Attachment Release Penetration Biosynthesis Maturation

53 Lysogenic Bacteriophage Cycle Lytic Cycle

54 Animal Unenveloped DNA Viral Replication

55 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.

56 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.

57 Viruses and Cancer One of many factors

58 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.

59 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

60 Latency, Persistence and the Prions

61 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.

62 Graph of Acute, Latent and Persistent Viral Infections

63 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.

64 Prion Reaction PrP C + PrP Sc 2 PrP Sc