Microbiology and Taxonomy Review

Chapter 10: Classification of Microorganisms

  • Phylogenetic Relationships:

    • Taxonomy: The science of classifying organisms based on similarities.

    • Systematics: The study of evolutionary relationships among organisms, or phylogeny.

  • Limitations of Two-Kingdom Classification:

    • Does not adequately separate prokaryotes (bacteria and archaea) from eukaryotes.

  • Major Contributions:

    • Linnaeus: Developed the two-kingdom system (Plantae and Animalia).

    • Whittaker: Proposed a five-kingdom system.

    • Woese: Introduced the three-domain system based on rRNA sequences.

  • Advantages of the Three-Domain System:

    • Better reflects evolutionary relationships among organisms.

  • Characteristics of Bacteria, Archaea, and Eukarya:

    • Bacteria: Prokaryotic, possess peptidoglycan cell walls.

    • Archaea: Prokaryotic, distinct membrane lipids, lack peptidoglycan.

    • Eukarya: Eukaryotic, membrane-bound organelles.

  • Characteristics and Classification of Organisms:

    • Eukaryotic Species: Groups of closely related organisms that can interbreed.

    • Prokaryotic Species: Populations of cells with similar characteristics, comprising clones and strains.

  • Scientific Nomenclature:

    • Binomial Nomenclature: Uses genus and species to accurately name organisms, e.g., Streptococcus aureus.

  • Taxonomic Hierarchy:

    • Organisms classified through a series of taxonomic levels.

  • Classification of Eukaryotes:

    • Protista: Autotrophic and heterotrophic organisms, grouped based on rRNA.

    • Fungi: Chemoheterotrophic, with chitin cell walls.

    • Plantae: Multicellular organisms with cellulose cell walls, perform photosynthesis.

    • Animalia: Multicellular, lack cell walls, chemoheterotrophic.

  • Classification of Viruses:

    • Not categorized within the domains, as they are acellular and require a host for replication.

    • Viral Species: Defined by shared characteristics and ecological niches.

  • Methods of Classifying Microorganisms:

    • Classification: Grouping organisms based on shared traits.

    • Identification: Matching characteristics of an unknown microorganism against known organisms.

  • Bergey's Manual:

    • A key resource for determining bacterial and archaeal classifications.

  • Differential Staining and Identification:

    • Morphological characteristics help identify eukaryotes, while staining (e.g., Gram staining) aids bacterial identification.

  • Biochemical Tests:

    • Analyze bacterial enzymes and metabolic pathways.

  • Serological Testing:

    • Uses immune response analysis to identify organisms, particularly with techniques like ELISA and Western Blotting.

  • Phage Typing:

    • Identifies bacterial species' susceptibility to specific bacteriophages.

  • DNA Sequencing and Fingerprinting:

    • Used to compare genetic similarities and differences among organisms.

  • Nucleic Acid Hybridization:

    • Analytical method determining the relatedness of DNA from different organisms, including Southern Blotting and DNA chip technologies.

  • Evolutionary Relationships:

    • Explored through cladograms and dichotomous keys, showcasing evolutionary lineage.