classification of microorganisms – chapter 9
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Classification of Microorganisms – Chapter 9. Taxonomy The science of classifying organisms Provides universal names for organisms Provides a reference for identifying organisms Phylogeny The study of the evolutionary history of organisms. The Three-Domain System. Taxonomic Hierarchy. - PowerPoint PPT PresentationTRANSCRIPT
Classification of Microorganisms – Chapter 9
• Taxonomy
• The science of classifying organisms
• Provides universal names for organisms
• Provides a reference for identifying organisms
• Phylogeny
• The study of the evolutionary history of organisms
The Three-Domain System
Taxonomic Hierarchy
Species Definition• Eukaryotic species:
• A group of closely related organisms that breed among themselves and produce offspring that can produce offspring
• Viral species:
• Population of viruses with similar characteristics that occupies a particular ecological niche
• Prokaryotic species:• A population of cells with similar characteristics
•Based on:•morphology
•biochemistry
•genetics
Strain: Genetically different cells within a species
• Animalia: Multicellular; no cell walls; chemoheterotrophic
• Plantae: Multicellular; cellulose cell walls; usually photoautotrophic
• Fungi: Unicellular or multicellular; cell wall structure varies; Chemoheterotrophic
• Protista: A catchall for eukaryotic organisms that do not fit other kingdoms; Predominantly unicellular
Domain Eukarya
References
•• Bergey’s Manual of Determinative Bacteriology
•Provides identification schemes for identifying bacteria and archaea
•Morphology, differential staining, biochemical tests
•• Bergey’s Manual of Systematic Bacteriology
•Provides phylogenetic information on bacteria and archaea
•Based on rRNA sequencing
•• Approved Lists of Bacterial Names•Lists species of known prokaryotes
•Based on published articles
Identification Methods• Morphological characteristics: More useful for
identifying eukaryotes than prokaryotes
• Differential staining:
• Gram staining
• Acid-fast staining
• Special staining
• Negative staining
• (Endo)spore staining
Identification Methods
• Biochemical tests:
• Determines presence of specific bacterial
See Animations → Dichotomous Key (chapter 10 Microbiology Place CD or website)
Miniaturized Rapid Identification – “Enterotube”
Vitek 2 – a more advanced miniaturized rapid identification system
• Combine known antiserum + unknown bacterium or bacterial antigens
• Slide agglutination
• ELISA
• Western blot
Serology
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Another antibody-antigen test
• Rapid “Strep” throat test
• Detects Group A streptococci (i.e. Streptococcus pyogenes) in minutes.
• Can identify different cell types
• Fluorescently labelled antibodies are attached to cells
• Computer detects cells
Flow Cytometry
• DNA fingerprinting
• Electrophoresis of enzymatic digests
• rRNA sequencing
Genetics
Nucleic Acid Hybridization: DNA chip