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

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Presentation on theme: "Introduction: The microbial world, Classification, Taxonomy, Nomenclature."— Presentation transcript:

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

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

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

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

6 Prokaryotes Vs. Eukaryotes

7 Features of cells ProkaryoticEukaryotic Size0.3-2µm2-20µm ChromosomeSingle, circularMultiple NucleusNo nuclear envelope; no nucleoli Membrane bound; nucleoli present Membrane bound organnelles Not presentPresent Ribosomes70S ribosomes (50S & 30S subunits) 80S ribosomes (60S & 40S subunits Cell wallUnique chemical components, peptidoglycan Not present (except in plant cells), no peptidoglycan Plasma membrane No carohydrates; most lack sterols Carbohydrates & sterols present Mitochodria Cytoskeleton & Chloroplasts NoYes Chloroplast only in plant & algae

8 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.

9 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: genus species Staphylococcus aureus Staphylococcusepidermidis

10 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)

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

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13 Gram-positive cocci Gram-negative bacilli

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15 Classification of Bacteria  True bacteria  Spirochaetes  Mycoplasmas  Riickettsiae & Chlamydiae  Filamentous bacteria

16 PROKARYOTES Diagrammatic structure of a bacterium

17 Comparison of Eukaryotic microbes HelminthsProtozoaFungi Multicellular Single celled Single or multicellular Cell organization Organic compounds derived from host Organic compounds Source of energy MacroscopicMicroscopic Microscopic or macroscopic Size

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

19 Parasites Classification

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

21 of medical importance Some Protozoa (unicellular) of medical importance Amoeboids (Pseudopods) Ciliates (cilia) Zooflagellates (flagella) Sporozoa (no locomotion) Entamoeba histolytica Entamoeba coli) Balantidium coliTrichomonas vaginalis Giardia lamblia Leishmania tropica Plasmodium Toxoplasma gondii Cryptosporidium

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

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

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

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

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

28 Defense against microbes Innate immunity Innate immunity Inborn, non-specific Inborn, non-specific Adaptive immunity Adaptive immunity Acquired, specific, Immunological memory Acquired, specific, Immunological memory


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