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Introduction: The microbial world, Classification, Taxonomy, Nomenclature

Introduction: The microbial world, Classification, Taxonomy, Nomenclature. Objectives. To understand the broad classification of microbes as bacteria, fungi, protozoa, helminths , viruses, and prions To know the differences between prokaryotes and eukaryotes

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Introduction: The microbial world, Classification, Taxonomy, Nomenclature

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  1. Introduction: The microbial world, Classification, Taxonomy, Nomenclature

  2. Objectives • To understand the broad classification of microbes as bacteria, fungi, protozoa, helminths, viruses, and prions • To know the differences between prokaryotes and eukaryotes • To discuss the basis of bacterial taxonomy • To have an overview of the morphology,staining and lifecycles of bacteria, fungi, protozoa, and helminthes • To outline the immune response for protection against microbial invasion

  3. } = Prokaryote = Eukaryote Three Domains • All living organisms can be classified into one of three major groups called domains • Bacteria • Archaea • Eukarya

  4. Bacteria & Archaea • Both have same shape, size & appearance • Major differences exist in their chemical composition • Archaea • lack peptidoglycan • means "ancient" because use ancient energy mechanisms • Grow in harsh environments e.g high salt, very high temp

  5. Classes of infectious organisms Eukaryotes Arthropods(insects, ticks & mites) Helminthes (worms) Fungi Protozoa Prokaryotes Archaea Bacteria Viruses Prions

  6. Prokaryotes Vs. Eukaryotes

  7. Domain Kingdom Phyla Class Order Family Genus Species Microbial taxonomy is commonly called prokaryotic taxonomy. The widely accepted prokaryotic taxonomy is Bergey’s Manual of Systematic Bacteriology, first published in 1923 by the American Society for Microbiology.

  8. Bacterial Naming • Adopts the species and generic names • Species: • basic unit of classification • collection of strains with common characteristic • Genus (plural: Genera) • group of bacterial organisms having in common several structural, biochemical & physiological traits • Group of species make up the genus • Every organism is identified by its genus and species • The generic name is the first name and starts with a capital letter • The species name is the second name and starts with a small letter Example: genusspecies Staphylococcus aureus Staphylococcus epidermidis

  9. Bacterial classification - mixture of characteristics • Macroscopic • Colonies: color, size, shape, smell • Haemolytic/ non-haemolytic • Special growth requirements • Microscopic • Shape: cocci, rods, curved, or spiral • Staining properties • Respiration • Aerobic, Anaerobic, Microaerophilic • Reproduction: • Sporing, non-Sporing • Biochemical characteristics • Fermentation of sugars • Production of enzymes • Antigenicity • Molecular (Genotype)

  10. Microscopic • Size, shape and configuration of the organisms • cocci, rods, curved, or spiral • Ability to retain the Gram stain • gram-positive or gram-negative

  11. Gram-negative bacilli Gram-positive cocci

  12. Classification of Bacteria • True bacteria • Spirochaetes • Mycoplasmas • Riickettsiae & Chlamydiae • Filamentous bacteria

  13. PROKARYOTES Diagrammatic structure of a bacterium

  14. Comparison of Eukaryotic microbes

  15. Fungi Yeast cells e.g. Candida • Diverse group of saphrophytic organisms • getting nutrients from dead organic matter • Two basic forms: • Filamentous, mold-like: • Consist of threads(mycelia) that elongate and branch • Example: Mold & mushrooms • Yeast-like, single cells, round • Divide by budding, larger than bacteria • Example: Candida Fungal mould

  16. Parasites Classification

  17. Protozoa • Single-celled eukaryotes, larger than bacteria • Some are motile with flagella • Can have 2 forms during the lifecycle: • Trophozoite- larger form, metabolically active, motile, dividing • Cyst- smaller form, metabolically inactive, not dividing, can survive harsh conditions

  18. Some Protozoa(unicellular) of medical importance

  19. E. histolytica (trophozoite) E. coli (trophozoite) Iodine stained wet preparation Showing: Cystsof Entamoeba coli and Entamoeba histolytica E. coli cyst (more than 4 nuclei) E. histolytica cyst (4 nuclei) Edited by A. Qareeballa

  20. Protozoa: Flagellates Trichomonas vaginalis : Sexually transmitted One life cycle stage: Flagellated trophozoite Giardia lamblia : Transmitted by faeco-oral route Has a two life cycle stages: Flagellated trophozoite & Cyst

  21. Leishmania : Amastigote form inside macrophages PROTOZOA Ring stage of P. falciparum (malaria parasite)

  22. Helminths – worms Largest and multicellular Most have 3 stages in life-cycle: Egg Larva Adult

  23. Viruses • No cellular structure, not living cells • Obligate intracellular pathogens • Viruses must enter host cells to multiply & cause disease • Genome has DNA or RNA • surrounded by protein capsid coat

  24. Defense against microbes • Innate immunity • Inborn, non-specific • Adaptive immunity • Acquired, specific, Immunological memory

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