Classification of Microorganisms 2019.pptx

Microbiology

1. Classification of microorganisms, growth properties and characteristics Wewedru Izale , MSc (ID) Microbiology Department, MNRH

2. Introduction The science of organizing, classifying and naming of organisms is called taxonomy. The word comes from the Greek taxis, 'order', nomos , 'law' or 'science'. Taxonomy: Identification - characterizing organisms Classification - arranging into similar groups Nomenclature - naming organisms Prokaryote classification involved techniques used to characterize and identify prokaryotes e.g.. microscopic examination , cultural characteristics, biochemical testing, nucleic acid analysis

3. Taxonomy Taxonomic classification, categories are arranged in hierarchical order and species is basic unit: Domain Kingdom Phylum (pl: Phyla) or Division Class Order Family Genus (pl: Genera ) Species (pl: Species )

4. Taxonomy… Domain/Kingdom Bacteria Phylum Schizomycophyta Class Schizomycetes Order Enterobacteriales Family Enterobacteriaceae Genus Shigella Species dysenteriae

5. Taxonomy… Definition of “species” in microbiology; Type strains: “Known” well-characterized pure cultures; references for the identification of unknowns American Type Culture Collection (ATCC)

6. Taxonomy… Species” vs. “Strain” Species: A specific or defined type of organism, defined by similarity with known species. Strain: Genetic variation within a species.

7. Taxonomy… Nomenclature Scientific name (Systematic Name) Binomial System of Nomenclature Genus name + species name italicized or underlined genus name is capitalized and may be abbreviated species name is never abbreviated. e.g. Bacillus subtilis       B. subtilis

8. Taxonomy… Nomenclature (cont.) Common or descriptive names (trivial names) eg : tubercle bacillus         ( Mycobacterium tuberculosis ) meningococcus ( Neiserria meningitidis ) Group A streptococcus ( Streptococcus pyogenes )

9. Importance of taxonomy Allows the organization of huge amounts of knowledge about the organisms . Allows for predictions & frame hypothesis for further research based on knowledge of similar organisms. Places microorganisms in meaningful and useful groups with precise names . Provides accurate identification of microorganisms (e.g. the need to know the pathogen for a clinical test). Microbial Evolution & Diversity. Universal Phylogenetic Tree.

10. Classification Systems Microscopic morphology ( morphology & staining reaction ) Macroscopic morphology – colony appearance Physiological / biochemical characteristics Chemical analysis Serological analysis Genetic and molecular analysis; G + C base composition DNA analysis using genetic probes Nucleic acid sequencing and rRNA analysis

11. Classification System… Phage typing Bacteriocine typing Animal pathogenicity and Toxigenicity Antimicrobial susceptibility testing.

12. Classification of Microorganisms: Microbes can be classified into four major groups: Protozoa, fungi, viruses and bacteria . 1. Protozoa : These are unicellular organisms with protoplasm differentiated into nucleus and cytoplasm. Diameters in the range of 2-100 μm . The most important groups of medical protozoa are: Amoeba : Entamoeba species. Mode of Motility: pseudopodia.

13. Mastigophora : Mode of Motility: the Flagella. Gastrointestinal flagellates : Giardia intestinalis Urogenital flagellates: Trichomonas vaginalis Tissue and blood flagellates: Trypanosoma , Leishmania

14. Trypanosoma , and Leishmania .

15. Ciliophora : motile by cilia. Example: Balantidium coli .

16. Sporozoa : intracellular infection. Example: Plasmodium that cause Malaria.

17. 2- The Fungi Fungi are saprophytic or parasitic organisms possessing relatively rigid cell walls. Medical fungi: Moulds: Branching filaments; hyphae, mycelium. Usually 2 to 10 μm in width. e.g. Epidermophyton , Trichophyton , Microsporum , Aspergillus . 2. True Yeasts: Ovoid or spherical cells that reproduce asexually by budding or fission and sexually with formation of spores. e.g. Cryptococcus spp . 3. Dimorphic fungi: Produce a vegetative mycelium at room temperature but are yeast like in i nfected lesions/tissue e.g.: Histoplasma . 4- Yeast- like fungi: e.g : Candida ( Pseudomycelium ).

18. 3- The viruses: Viruses consist of DNA or RNA enclosed in a simple protein shell known as a capsid. General properties of viruses: They are very small in size, from 10-400 nm . They contain one kind of nucleic acid (RNA or DNA) as their genome. They are metabolically inert They are obligate intracellular parasites. They are only seen by electron microscope. Depend on the parasitized cell for survival and multiplication

19. 4. The Bacteria Bacteria are classified and identified to distinguish one organism from another ,and to group similar organisms by criteria of interest to microbiologists or other scientists. Bacteria can be classified by: 1. colony shape in culture 2. motility 3. morphological characteristics other than shape e.g. multiple flagella 4. metabolic activity ( Biochemical reactions) eg . sugars they ferment 5. DNA sequence 6. Gram stain reactions

20. Classification of bacteria Bacteria can be classified according to morphology and staining reaction into the following groups: a) Higher bacteria : Filamentous bacteria: Streptomyces (antibiotic producers). b)True bacteria/lower bacteria : 1.Cocci : Gram positive: Staphylococcus, Streptococcus. Gram negative: Neisseria . 2. Bacilli: Gram positive: Bacillus, Clostridum , Corynebacterium . Gram negative: Enterobacteriaceae , Brucella . 3. Spirochetes : Slender flexuous spiral bacteria . E.g. Borrelia , Treponema , Leptospira . 4. Mycoplasma: The Smallest bacteria that lack of a rigid cell wall. 5. Rickettsiae and Chlamydiae : intracellular parasites.

21. Morphological Classification: Morphology and arrangement of bacterial cells are criteria used for classification of bacteria into following groups: 1. Cocci (singular : coccus ). 2 . Rods (bacilli), (singular : rod, bacillus). 3 . Vibrios (singular : vibrio). 4. Spirilla (singular : Spirillum ) 5. Spirochaetes . (Singular: s pirochaete ). 1. Cocci : Round or oval bacteria measuring about 0.5-1.0 µm in diameter. When they are multiplying , cocci may form pairs, chains, or irregular groups.

22. Cocci in pairs are called diplococci , e.g.meningococci and gonococci. Cocci in chains are called streptococci, e.g. Streptococcus pyogenes . Cocci in irregular groups are called Staphytococci , for example, Staphylococcus aureus

23. 2. Rods (bacilli): These are stick-like bacteria with rounded, square, or swollen ends. They measure 1-10 µm in length by 0.3-1.0 µm in width. It may arranged in: A- Chains, for example, Streptobacillus species. B- Branching chains, for example, lactobacilli . C- Mass together, for example, Mycobacterium leprae . D- Remain attached at various angles resembling Chinese letters, for

24. 3-Vibrios: These are small slightly curved rods measuring 3-4 µm in length by 0.5 µm in width. Most vibrios are motile with a single flagellum at one end and show a rapid darting motility. E.g. Vibrio cholerae .

25. 4-Spirochetes: These are flexible, coiled, motile organism, 6-20 µm in length. They progress by rapid body movements. Spirochetes are divided into three main groups: A- Treponemes . B- Borreliae . C- Leptospires

26. Cultural characteristics Bacteria show characteristic type of growth on solid media under appropriate cultural conditions . Colony morphology can be used in presumptive identification. Colonies can be varying in size and diameter, in outline (circular, wavy, rhizoid etc.) elevation ( flat, raised, convex, etc.) and translucency (transparent, opaque, and translucent ). Colonial colour or the changes that they bring about in their surroundings is also used as diagnostic tools in the tentative identification of the bacteria e.g. β – and α – hemolytic colonies.

27. Aerobic and anaerobic conditions Bacteria are also classified based on the requirement of oxygen for their survival . Aerobes use oxygen for respiration. Anaerobes do not use oxygen for respiration. Microaerophiles require low oxygen concentration. Facultative anaerobes can survive in presence or absence of oxygen. Obligate aerobes cannot survive without oxygen. Obligate anaerobes cannot survive in presence of oxygen.

28. Autotrophs and Heterotrophs Autotrophic bacteria obtain carbon from CO2 or use sunlight. Heterotrophic bacteria obtain sugar from the environment ( e.g.living cells/organisms).

29. Classification based on environment/ecology Mesophiles - which require moderate conditions to survive. Neutrophiles - which require moderate conditions to survive. Extremophiles - which can survive in extreme conditions. Acidophiles - which can tolerate low pH conditions. Alkaliphiles - which can tolerate high pH conditions.

30. Classification based on environment/ecology… Thermophiles - which can resist high temperature . Psychrophilic bacteria - which can survive extremely cold conditions . Halophiles - which can survive in highly saline conditions . Osmophiles - which can survive in high sugar osmotic conditions.

31. The End!