Session 4 - Taxonomy

• taxis


  arrangement or order
• nomos


  Greek word that means "law"
• nemein


  means to distribute or govern.\
• Taxonomy


  the science of biological classification.
• Taxa or Taxon


  a group or level of classification or hierarchy categorized at different levels
• Systematics or phylogeny


  the study of diversity of organism and their evolutionary relationship
• Dichotomous Key


  means of assigning an organism to a specific taxonomic category.
• Taxonomic categories or hierarchy


  An ordered group of taxonomic ranks used to classify organisms from general to specific
• Taxonomic Categories (from general to specific)

  Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
• What are the five (5) major taxonomic characteristics:

  • Morphological characters
  • Physiological characters
  • Geographic and behavioral characters
  • Molecular Characters
  • Ecological Characters
• Morphological characters

  • General external and internal morphology
  • Special structures
  • Embryology
  • Karyology and other cytological factors
• Physiological characters

  • Metabolic factors
  • Body secretions
  • Genic sterility factors
• Molecular characters

  • Immunological distance
  • Electrophoretic differences
  • DNA hybridization
  • DNA-RNA sequence
• Ecological Characters

  • Habitats
  • Food
  • Seasonal variation
  • Parasite and host
• Classification


  taxa are classify based on the similarities in phenotypic (phenetic) characteristics which are expressed in an organism and can be examined visually or can be tested by other means.
• What are the three (3) systems of Classification?

  Artificial, Natural, Phylogenetic
• Artificial System 


  share the same characteristics but they are not closely related to one another genetically.
• Natural System 


  with many of the same characteristics and highly predictive.
• Phylogenetic (Phyletic) System


  classifying organism on the basis of descent from a common ancestor.
• Methods of Classification:

  1. Phenotypic (Phenetic) Classification System
  2. Genotypic Classification System
• Phenotypic (Phenetic) Classification System - groups do not necessarily reflect genetic similarity or evolutionary relatedness. Instead, groups are based on convenient, observable characteristics.

  Genotypic Classification System - - considers characteristics of the genome.
• Classification on Hierarchy

  1. Family
  2. Genus
  3. Species
• Species

  • groups of populations that can potentially interbreed freely within and among themselves.
  • collection of bacterial strains that share common physiologic and genetic features and differ notably from other microbial species.
• Subspecies


  are taxonomic subgroups within a species
• Clone


  is a population of cells derived from a single parent cell and identical.
• Strain


  came from pure cultures of the same species are not identical in all ways.
• Subspecies:

  1. Biotype - a group of organisms having the same or nearly the same genotype
  2. Serotype - a group of organisms within a species that have the same type and number of surface antigens.
  3. Genotype may be given to groups below the subspecies level that share specific but relatively minor characteristics.
• Types of Strains:

  1. Serovar
  2. Biovar
  3. Morphovar
  4. Isolate
• Serovar


  a strain differentiated by serological means. Strains vary in their antigenic properties.
• Biovar


  strains that are differentiated by biochemical or other non-serological means.
• Morphovar


  a strain which is differentiated on the basis of morphological distinctions.
• Isolate


  a pure culture derived from a heterogeneous, wild population of microorganisms.
• Strain Differentiation Methods:

  1. Protein Profile
  2. Immunological Reaction
  3. Flow Cytometry
  4. Phage Typing
• Nomenclature


  branch of taxonomy concerned with the assignment of names to taxonomic groups in agreement with published rules.
• Carolus Linnaeus


  He introduced a formal system of classification dividing living organisms.
• Every organism is assigned a genus and a species of Latin or Greek derivation by the addition of the appropriate suffix.
• Microorganisms are named according to established rules and guidelines set forth in the International Code of Nomenclature of Bacteria (ICNB) or the Bacteriological Code (BC).
• The taxonomic classification scheme for prokaryotes is found in Bergey’s Manual of Systematic Bacteriology.
• Rules governing microbial nomenclature is limited to two taxa, genus and species known as binomial nomenclature.
• Pointers on How to write the scientific name:

  1. Suffixes for order and family are written as -ales and –aceae.
  2. The genus and specific epithet (species), both names are printed underlined or italicized.
  3. The genus name is always capitalized in first letter and is always a noun. The species name is lowercase in first letter and is usually an adjective.
  4. The name may be abbreviated by using the uppercase form of the first letter of the genus designation followed by a period (.) and the full species name, which is never abbreviated.