1. Lecture 5: Survey of the microbial world Edith Porter, M.D. 1

2.  Classification of microorganisms ▪ Taxonomy ▪ Three domain system: Bacteria, Archaea, Eukarya  Prokaryotes ▪ Bacteria ▪ Archaea  Eukaryotes ▪ Protozoa ▪ Algae ▪ Fungi ▪ Helminths 2

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4.  The science of classifying organisms  Provides universal names for organisms  Provides a reference for identifying organisms  Initially based on morphology and biochemical assays  Now based on nucleic acid sequencing (16S and 18S rRNA analysis) 4

5.  The study of the evolutionary history of organisms  All Species Inventory (2001–2025)  To identify all species of life on Earth  Species definition  Eukaryotes: breed among themselves  Prokaryotes: > 97% homology in 16S rRNA  Cladograms used to establish relation ship 5

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11. Taxonomy is the science of classification using a hierarchical system Universal ancestor The three domains differ in presence of a nucleus (eukarya), ether linked lipids (archaea) and use of formylmethionine as started amino acid in protein synthesis (bacteria) Cladograms are used to establish evolutionary relationships 11

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14.  Obligate intracellular bacteria  Cannot proliferate outside of a host cell  Selected human pathogens  Rickettsia  Chlamydia 14

15.  Transmitted by ticks or lice  Infects vascular endothelial cells  R. rickettsii: Rocky Mountain spotted fever 15 http://www.lincolner.com/Lincoln %20page%203/images/rocky%2 0mountain%20spotted%20fever 1.jpg

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19. 19  Eukaryotic  Aerobic or facultatively anaerobic  Chemoheterotrophic  Most are decomposers  Asexual and sexual spore formation  For Reproduction, not endurance!!  Broad use of fungi  Food, food production, drugs  Mycology is the study of fungi

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21. YEASTS  Unicellular  Proliferate by budding or fission  Candida albicans MOLDS  Multicellular  Septated and unseptated hyphae  Mass of hyphae is mycelium  Aspergillus spec., Rhizopus spec. 21

22.  Switch growth phase depending on environmental conditions  Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C 22

23.  Systemic mycoses: Deep within body  Subcutaneous mycoses: Beneath the skin  Cutaneous mycoses: Affect hair, skin, and nails  Superficial mycoses: Localized, e.g., hair shafts  Opportunistic mycoses: Caused by normal microbiota or environmental fungi  Note: antibiotics do not work against fungi! 23

24. 24  Yeasts  Candida: Candidiasis  Cryptococcus: Meningitis  Molds  Aspergillus: Lung infection in neutropenic patients  Rhizopus, Mucor: in diabetes patients  Dimorphic  Coccidioides: Lung infections  Histoplasma: Lung infections  Dermatophytes  Trichophyton, Epidermophyton: Tinea

25.  Eukaryotic  Always unicellular  Chemoheterotrophs  Digestion in vacuoles  Often complex life cycles with multiple hosts and vectors  Some produce cysts  Resistant survival forms  Vegetative form is a trophozoite  Reproduction  Asexual  Sexual reproduction 25

26.  Archaezoa: Trichomonas, Giardia  Amaebazoa: Entamoeba  Apicomplexa: Plasmodium  Ciliophora: Balantidum  Euglenozoa: Trypanosoma 26

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29.  Eukaryotic  Multicellular, organ differentiation  Kingdom: Animalia  Phylum: Platyhelminthes (flatworms) ▪ Class: Trematodes (flukes) ▪ Class: Cestodes (tapeworms)  Phylum: Nematodes (roundworms)  Chemoheterotrophic  Multiple hosts  Intermediate host  Definitive host: adult form develops, sexual reproduction 29

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31.  Monoecious (hermaphroditic)  Male and female reproductive systems in one animal  Dioecious  Separate male and female  Egg  larva(e)  adult 31

32.  Oral sucker: food uptake  Incomplete digestive tract  Ventral Sucker: Attachment  Mostly hermaphroditic (monoecious) 32

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34.  Sucker for attachment  No digestive tract  Food uptake by absorption  Hermaphrodites (monoecious)  Scolex, neck, proglottides 34

35.  Dioecious (male, female)  Complete digestive tract  Caenorrhabditis elegans: model system Necator americanus (hook worm) 35

36.  Fungi  Molds (septated, unseptated), yeast, dimorphic  Sexual and asexual spores  Mycoses: local or systemic impairment of host defense  Protozoa: always unicellular, often vectors  Helminths: always multicellular, complex life cycles 36

37. 37  Eukaryotic  Multicellular, organ differentiation  Kingdom: Animalia  Phylum: Platyhelminthes (flatworms) ▪ Class: Trematodes (flukes) ▪ Class: Cestodes (tapeworms)  Phylum: Nematodes (roundworms)  Chemoheterotrophic  Multiple hosts  Intermediate host  Definitive host: adult form develops, sexual reproduction