Classification of
Microorganism
lecture V
 Taxonomy
(Greek) ---taxis to
arrange, to order
nomos
law
The science of classifying organisms
Provides universal names for organisms
Provides a reference for identifying
organisms
Species Definition
 Eukaryotic
species:
A group of closely related
organisms that breed among
themselves
Species Definition
 Prokaryotic species:
A
population of cells with similar
characteristics (same growth
requirements etc.)
Clone: Population of cells derived
from a single cell (pure culture
concept)
Strain: Genetically different cells
within a clone (E.coli 0157:H7)
Species Definition
Viral
species:
Population of viruses with
similar characteristics
(Enteroviruses—Polio,Coxsackie
& Echovirus) that occupies a
particular ecological niche (GI
tract)
Taxon (sn.) Taxa (pl.)
Arrangement
of organisms
into taxonomic categories
Reflect degree of
evolutionary (phylogenetic)
relatedness
Classification history
Aristotle
Plants,
or
Animals
Classification history (cont.)
 Edward
Chatton (1937)
Introduced the term
procaryote
Cells without nucleus
Classification history (cont.)
 Robert
H. Whittaker (1969)
 Five-Kingdom System
 Animals
 Plants
 Fungi
 Protista
 Procaryotes
Five-Kingdom System (cont.)
 Based
on physical description
Nutritional
requirements
Patterns of development
Type of flagella
Five-Kingdom System
 Considers
procaryotes (bacteria)
the ancestors of all eucaryotes
Kingdom Procaryotae
(bacteria)
 Unicellular
 Asexual
reproduction
 Flagella composed of flagellin
 Adsorptive nutrition
Categories of procaryotes
(bacteria)
 With
cell wall
 Gram + and Gram  Archaeobacteria
 Without cell wall
 Mycoplasma
Gram negative
Outer and inner membranes
 Thin peptidoglycan
 No endospore-forming

Gram positive
 No
outer membrane
 Thick peptidoglycan
 Some spore-forming
Archaeobacteria
 Extreme
environments
 Cell wall (no peptidoglycan)
 Share some genetic features with
eucaryotes
Bacteria without cell wall
Mycoplasma
Highly
pleomorphic
Very small
Sterols (as eucaryotes)
Kingdom Protista
 Mostly unicellular
 Multicellular lack tissue
organization
Vorticella
 All asexual reproduction, many
sexual
 Phagocytosis
 Flagella formed by microtubules
Kingdom Fungi
 Unicellular
yeast
 Multicellular molds
 Mushrooms
 Absorptive nutrition
 Most lack flagella
Kingdom Plantae
 All
multicellular
 Green algae, Mosses and Ferns
 Conifers and flowering plants
Kingdom Plantae (cont.)
 Photosynthetic
nutrition
 Mostly sexual reproduction
Kingdom Animalia
 All
multicellular
 Sponges, worms, insects, etc.
 Ingestive nutrition
 Sexual reproduction
Classification history (cont.)
 Carl
R. Woese (1978)
3 domains
Based on molecular
characteristics of
ribosomal RNA
Ribosomal RNA (rRNA)
nucleotide sequencing
Homology (%)
agg uag cug cug gga cca cga ggg aca gac
agg uag auc cug gga cca gga ggg aca gac
agg gua cau cug gga cca cga cac aca cag
a= adenine
g= guanine
u= uracil
c= cytosine
90
70
RNA building blocks
Eubacteria
Gram +
Myco-
Archea
Methanogens
Eucarya
Animals
Plants-Fungi
Gram
plasma
Halophiles
Thermoacidophiles
Unknown ancestor
Protists
Prokaryotes
Figure 10.6
Endosymbiotic Theory
Figure 10.2
Figure 10.3
Three-Kingdom System
 Based
on Molecular biology and
biochemistry mostly rRNA
sequencing
Archaea
Eubacteria
Eucaryotes
Three-Kingdom System (cont.)
 Archaeobacteria
(unusual cell
walls no peptidoglycan)
 Eubacteria (peptidoglycan)
 Eucaryotes (plants, animals, fungi
and protists)
Taxonomic hierarchy
 Kingdom
 Phylum
 Class
 Order
 Family
 Genus
 Species
•Enterobacteriaceae
•Escherichia
•coli
Binomial System
 Carolus

Linneaus
Two-parts latinized, italicized name
 i.e. Escherichia (genus) coli (species)
 Escherichia spp.
Strains
Minor
differences within same
species
Derived from one cell
More than 50 strains of
pathogenic E. coli
E.
coli strain O157:H7
E. coli strain O55
Source
of
Genus
Scientific binomial
name
Kbebsiella pneumoniae Honors Edwin
Klebs
Pfiesteria piscicida
Honors Lois
Pfiester
Salmonella
Honors Daniel
typhimurium
Salmon
Streptococcus pyogenes Chains of cells
(strepto-)
Penicillium notatum Tuftlike (penicill-)
Trypanosoma cruzi
Corkscrew-like
(trypano-, borer;
soma-body)
Source of
Specific epithet
The disease
Disease in fish
Stupor (typh-) in
mice (muri-)
Forms pus (pyo)
Spores spread in
wind (nota)
Honors
Oswaldo Cruz
Bergey’s Manual of Systematic
Bacteriology
Gram staining
 Cell wall
 Type
 Presence
 Phage typing

Biochemical
characteristics
 Serological tests
 Nucleic acid
characteristics

Testing methods used to differentiate
organisms and place them into the
right category
Bacteriophages
 Bacterial
viruses
Mobilization of genes
among bacteria
Diphteria toxin
Phage Typing
Figure 10.13
Dichotomous Key
Serology




Combine known antiserum +
unknown bacterium
Slide agglutination
ELISA
Western blot
Figure 10.10
Genetics

DNA base composition


DNA fingerprinting



Guanine + cytosine
moles% (GC)
Electrophoresis of
restriction enzyme
digests
rRNA sequencing
Polymerase Chain
Reaction (PCR)
Figure 10.14
Classification of Viruses
Non-cellular
organisms
 Family, genus, species and
strains
 Non-binomial,
i.e.
Human immunodeficiency
virus (HIV)
Rotavirus
Viral species
Population
of viruses with
similar morphology, and
nucleic acid, that infect similar
cells
 DNA
Type of nucleic acid
or RNA Never both!!
DNA
single stranded (ss)
double stranded (ds)
RNA
single stranded (ss)
double stranded (ds)