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 Three Domains = Eukaryote
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
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. Features of cells Prokaryotic Eukaryotic Size 0.3-2µm 2-20µm
Chromosome
Single, circular
Multiple
Nucleus
No nuclear envelope; no nucleoli
Membrane bound; nucleoli present
Membrane bound organnelles
Not present
Present
Ribosomes
70S ribosomes (50S & 30S subunits)
80S ribosomes (60S & 40S subunits
Cell wall
Unique chemical components, peptidoglycan
Not present (except in plant cells), no peptidoglycan
Plasma membrane
No carohydrates; most lack sterols
Carbohydrates & sterols present
Mitochodria Cytoskeleton
& Chloroplasts No
Yes
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
Staphylococcus epidermidis

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

13. Gram-negative bacilli
Gram-positive cocci

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

16. PROKARYOTES
Diagrammatic structure of a bacterium

17. Comparison of Eukaryotic microbes
Helminths
Protozoa
Fungi
Multicellular
Single celled
Single or multicellular
Cell organization
Organic compounds derived from host
Organic compounds
Source of energy
Macroscopic
Microscopic
Microscopic or macroscopic
Size

18. Fungi 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
Yeast cells e.g. Candida
Fungal mould

19. Parasites Classification

20. 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

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

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

23. 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

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

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

26. Nematehelminths (Nematodes or round worms)
Platyhelminths
(flat worms
Cestodes
e.g. Tape worm
Trematodes (Flukes)
e.g. Schistosoma
Nematehelminths (Nematodes or round worms)
E.g. Ascaris

27. 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

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