MICR 201 Microbiology for Health Related Sciences

1. Lecture 5: Survey of the microbial world Edith Porter, M.D. MICR 201 Microbiology for Health Related Sciences

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

3. Classification of microorgansims

4. Taxonomy • 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)

5. Phylogeny (or systematics) • 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

6. Cladogram to Establish the Evolutionary Relationship of Microorganisms

7. Three domain system (Carl Woese)

8. Model of the origin of eukaryots

9. Major differences between domains (1)

10. Major differences between domains (2)

11. Important to Remember • 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

12. Prokaryotes

13. The Prokaryotes

14. Selected bacterial life forms • Obligate intracellular bacteria • Cannot proliferate outside of a host cell • Selected human pathogens • Rickettsia • Chlamydia

15. Rickettsia • Transmitted by ticks or lice • Infects vascular endothelial cells • R. rickettsii: Rocky Mountain spotted fever http://www.lincolner.com/Lincoln%20page%203/images/rocky%20mountain%20spotted%20fever1.jpg

16. Chlamydia (1)

17. Chlamydia (2)

18. Eukaryotes

19. Fungi • 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

20. Comparison of fungi and bacteria , absorptive

21. Yeast and molds Yeasts Molds Multicellular Septated and unseptated hyphae Mass of hyphae is mycelium Aspergillus spec., Rhizopus spec. • Unicellular • Proliferate by budding or fission • Candida albicans

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

23. Fungal diseases • 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!

24. Medically relevant fungi • 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. Protozoa • 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

26. Medically Important Phyla of Protozoa • Archaezoa: Trichomonas, Giardia • Amaebazoa: Entamoeba • Apicomplexa: Plasmodium • Ciliophora: Balantidum • Euglenozoa: Trypanosoma

27. Life cycle of Plasmodium vivax

28. Helminths

29. Characteristics of Helminths • 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

31. Life Cycle of Helminths • Monoecious (hermaphroditic) • Male and female reproductive systems in one animal • Dioecious • Separate male and female • Egg  larva(e)  adult

32. Trematodes (Flukes) • Oral sucker: food uptake • Incomplete digestive tract • Ventral Sucker: Attachment • Mostly hermaphroditic (monoecious)

33. Life Cycle of Paragonimus westermani (Lung fluke)

34. Cestodes(Tape Worms) • Sucker for attachment • No digestive tract • Food uptake by absorption • Hermaphrodites (monoecious) • Scolex, neck, proglottides

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

36. Important to Remember • 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

37. Helminths • 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