Chapter 10Chapter 10

Classification of Classification of MicroorganismsMicroorganisms

TaxonomyTaxonomy TaxonomyTaxonomy

The science of classifying organismsThe science of classifying organisms Provides universal names for organismsProvides universal names for organisms Provides a reference for identifying Provides a reference for identifying

organisms e.g from an infectionorganisms e.g from an infection

PhylogenyPhylogeny The study of the evolutionary history of The study of the evolutionary history of

organismsorganisms

History of TaxonomyHistory of Taxonomy 17351735 Plant and Animal KingdomsPlant and Animal Kingdoms 18571857 Bacteria & fungi put in the Plant KingdomBacteria & fungi put in the Plant Kingdom 18661866 Kingdom Protista proposed for bacteria, Kingdom Protista proposed for bacteria,

protozoa, algae, & fungi protozoa, algae, & fungi 19371937 "Prokaryote" introduced for cells "without a "Prokaryote" introduced for cells "without a

nucleus" nucleus" 19611961 Prokaryote defined as cells in which Prokaryote defined as cells in which

nucleoplasm is not surrounded by a nucleoplasm is not surrounded by a nuclear nuclear

membranemembrane 19591959 Kingdom FungiKingdom Fungi 19681968 Kingdom Prokaryotae proposedKingdom Prokaryotae proposed 19781978 Two types of prokaryotic cells found (bacteria & Two types of prokaryotic cells found (bacteria &

Archae)Archae)

The Three-Domain SystemThe Three-Domain System

Figure 10.1

The Three-Domain SystemThe Three-Domain System

Table 10.1

Table 10.2

Endosymbiotic Theory: Origin of Endosymbiotic Theory: Origin of EukaryotesEukaryotes

Figure 10.3

Figure 10.2

Classification of OrganismsClassification of Organisms

Living organisms are grouped according to similar Living organisms are grouped according to similar characteristicscharacteristics

Each organism is assigned a unique scientific nameEach organism is assigned a unique scientific name

Binomial nomenclatureBinomial nomenclature Every organism is assigned 2 namesEvery organism is assigned 2 names genus namegenus name; always capitalized, usually a noun; always capitalized, usually a noun species name (specific epithetspecies name (specific epithet); lowercase, usually an ); lowercase, usually an

adjectiveadjective Both names are printed underlined or italicizedBoth names are printed underlined or italicized Example Example Homo sapiens; Homo sapiens; homo means man, sapiens means homo means man, sapiens means

wisewise

Examples of Scientific NamesExamples of Scientific Names

Scientific binomialScientific binomial Source of Genus nameSource of Genus name Source of Source of Specific epithetSpecific epithet

Kbebsiella pneumoniaeKbebsiella pneumoniae Honors Edwin KlebsHonors Edwin Klebs The diseaseThe disease

Pfiesteria piscicidaPfiesteria piscicida Honors Lois PfiesterHonors Lois Pfiester Disease in fishDisease in fish

Salmonella typhimuriumSalmonella typhimurium Honors Daniel SalmonHonors Daniel Salmon Stupor (typh-) in mice Stupor (typh-) in mice (muri-)(muri-)

Streptococcus pyogenesStreptococcus pyogenes Chains of cells (strepto-)Chains of cells (strepto-) Forms pus (pyo-)Forms pus (pyo-)

Penicillium notatumPenicillium notatum Tuftlike (penicill-)Tuftlike (penicill-) Spores spread in wind Spores spread in wind (nota)(nota)

Trypanosoma cruziTrypanosoma cruzi Corkscrew-like (trypano-, Corkscrew-like (trypano-, borer; soma-body)borer; soma-body)

Honors Oswaldo CruzHonors Oswaldo Cruz

Taxonomic HierarchyTaxonomic Hierarchy

Figure 10.5

Species DefinitionSpecies Definition Eukaryotic speciesEukaryotic species::

A group of closely related organisms that breed A group of closely related organisms that breed among themselvesamong themselves

Prokaryotic speciesProkaryotic species:: A population of cells with similar characteristicsA population of cells with similar characteristics Clone: Population of cells derived from a single Clone: Population of cells derived from a single

cellcell Strain: Genetically different cells within a cloneStrain: Genetically different cells within a clone

Viral speciesViral species:: Population of viruses with similar characteristics Population of viruses with similar characteristics

that occupies a particular ecological nichethat occupies a particular ecological niche

Kingdom AnimaliaKingdom Animalia: : Multicellular; no cell walls; chemoheterotrophicMulticellular; no cell walls; chemoheterotrophic

Kingdom Plantae:Kingdom Plantae: Multicellular; cellulose cell walls; usually Multicellular; cellulose cell walls; usually

photoautotrophicphotoautotrophic

Kingdom Fungi:Kingdom Fungi: Unicellular or multicellular;Unicellular or multicellular; Chemoheterotrophic; Chemoheterotrophic;

cell walls of chitin; develop from spores or hyphal cell walls of chitin; develop from spores or hyphal fragmentsfragments

Kingdom Protista:Kingdom Protista: A catchall for eukaryotic organisms that do not fit A catchall for eukaryotic organisms that do not fit

other kingdomsother kingdoms

Classification of Eukaryotes; Domain Classification of Eukaryotes; Domain EukaryaEukarya

Classification of VirusesClassification of Viruses

Are not classified as part of the 3 domainsAre not classified as part of the 3 domains Are not composed of cellsAre not composed of cells Use the host cells machinery to multiplyUse the host cells machinery to multiply Are obligate intracellular parasites Are obligate intracellular parasites

Classification of Classification of ProkaryotesProkaryotes

Figure 10.6

ReferencesReferences

• Bergey’s Manual of Determinative Bergey’s Manual of Determinative BacteriologyBacteriology•Provides identification schemes for Provides identification schemes for identifying bacteria and archaeaidentifying bacteria and archaea

•Morphology, differential Morphology, differential staining, biochemical testsstaining, biochemical tests

•Bergey’s Manual of Systematic Bergey’s Manual of Systematic BacteriologyBacteriology•Provides phylogenetic information Provides phylogenetic information on bacteria and archaeaon bacteria and archaea

•Based on rRNA sequencingBased on rRNA sequencing

•Approved Lists of Bacterial NamesApproved Lists of Bacterial Names•Lists species of known prokaryotesLists species of known prokaryotes

•Based on published articlesBased on published articles

Identification MethodsIdentification Methods Morphological Morphological

characteristicscharacteristics: : Useful for Useful for identifying identifying eukaryoteseukaryotes

Differential Differential stainingstaining: Gram : Gram staining, acid-fast staining, acid-fast stainingstaining

Biochemical testsBiochemical tests: : Determines Determines presence of presence of bacterial enzymesbacterial enzymes

Figure 10.8

Identification MethodsIdentification Methods SerologySerology Combine known Combine known

antiserum antiserum (antibodies) + (antibodies) + unknown unknown bacteriumbacterium

Phage typingPhage typing Bacteriophages Bacteriophages

are bacterial are bacterial viruses. They are viruses. They are specific for specific for which bacteria which bacteria they infectthey infect Figure 10.10

DNA base composition Guanine + cytosine

moles% (GC)

DNA fingerprinting Electrophoresis of

restriction enzyme digests

rRNA sequencing

Polymerase Chain Reaction (PCR)

Figure 10.14

Identification MethodsIdentification Methods

Dichotomous KeyDichotomous Key