Classification of Microorganisms Part 1 Chapter 10 Classification of Microorganisms Part 1

Terminology Taxonomy Systematics or phylogeny The science of classifying organisms Provides universal names for organisms Provides a reference for identifying organisms Systematics or phylogeny The study of the evolutionary history of organisms

The Study of Phylogenetic Relationships All Species Inventory (2001-2025) To identify all species of life on Earth Historic Background 1735 Plant and Animal Kingdoms 1857 Bacteria & fungi put in the Plant Kingdom 1866 Kingdom Protista proposed for bacteria, protozoa, algae, & fungi 1937 "Prokaryote" introduced for cells "without a nucleus"

The Study of Phylogenetic Relationships 1961 Prokaryote defined as cells in which nucleoplasm is not surrounded by a nuclear membrane 1959 Kingdom Fungi 1968 Kingdom Prokaryotae proposed 1978 Two types of prokaryotic cells found (sequence in rRNA) 1979 Three domain system proposed (Woese) above 5 kingdoms (based on the rRNA nucleotide sequence)

The Three-Domain System Table 10.1

The Three-Domain System Figure 10.1

The Three-Domain System Table 10.2

Endosymbiotic Theory Figure 10.2 Figure 10.3

A Phylogenetic Hierarchy Implies that a group of organisms evolved from a common ancestor Some of the information used to classify comes from fossils Fossil evidence not available for most prokaryotes Phylogeny for prokaryotes based on DNA hybridization and rRNA sequencing

Classification of Organisms Rules for classifying and naming living organisms several scientific entities are responsible for establishing rules Scientific nomenclature (binomial nomenclature): genus and specific epithet (species) Bacteria or prokaryotic scientific names taken from Latin (genus can be taken from Greek) or Latinized by adding suffix “-ales” & “-aceae”. If reclassified, old name is often written in parentheses e.g. Enterococcus (Streptococcus) faecalis

References • Approved Lists of Bacterial Names Based on published articles • Approved Lists of Bacterial Names Lists species of known prokaryotes Based on rRNA sequencing • Bergey’s Manual of Systematic Bacteriology Provides phylogenetic information on bacteria and archaea Morphology, differential staining, biochemical tests • Bergey’s Manual of Determinative Bacteriology Provides identification schemes for identifying bacteria and archaea

Scientific Nomenclature Honors Oswaldo Cruz Corkscrew-like (trypano-, borer; soma-body) Trypanosoma cruzi Spores spread in wind (nota) Tuftlike (penicill-) Penicillium notatum Forms pus (pyo-) Chains of cells (strepto-) Streptococcus pyogenes Stupor (typh-) in mice (muri-) Honors Daniel Salmon Salmonella typhimurium Disease in fish Honors Lois Pfiester Pfiesteria piscicida The disease Source of Specific epithet Honors Edwin Klebs Kbebsiella pneumoniae Source of Genus name Scientific binomial

Taxonomic hierarchy Figure 10.5

Species Definition Eukaryotic species: a group of closely related organisms that breed (interbreed) among themselves but does not breed with individuals of another species Prokaryotic species: a population of cells with similar characteristics Clone: Population of cells derived from a single cell Strain: Genetically different cells within a clone

Domain Eukarya Animalia: Multicellular; no cell walls; chemoheterotrophic Plantae: Multicellular; cellulose cell walls; usually photoautotrophic Fungi: Chemoheterotrophic; unicellular or multicellular; cell walls of chitin; develop from spores or hyphal fragments Protista: A catchall for eukaryotic organisms that do not fit other kingdoms

Prokaryotes Figure 10.6

Classification of viruses Viral species: population of viruses with similar characteristics that occupies a particular ecological niche Viruses are not classified as part of the three-domain system Ecological niche of a virus is its specific host cell Viruses may be more closely related to their hosts than other viruses