PowerPoint PresentationMicrobiology
AN INTRODUCTION
EIGHTH EDITION
Taxonomy
Taxonomy
Provides a reference for identifying organisms
Goal of showing relationships among organisms
Taxon
Learning objectives:
Discuss the limitations of a 2-kingdom classification system.
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Cummings
Taxonomy
Systematics or phylogeny
The study of the evolutionary history of organisms and their
relationships
All Species Inventory (2001-2025)
Two-kingdom system not based upon natural classification based upon
ancestral relationships (e.g., DNA sequencing places fungi closer
to animals than plants)
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Cummings
Taxonomy History
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"
1961 Prokaryote defined as cells in which nucleoplasm is not
surrounded by a nuclear membrane
1959 Kingdom Fungi
1978 Two types of prokaryotic cells found
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The Three-Domain System
List characteristics of 3-domain system
Classified by cell type, cell wall, rRNA, membrane lipid structure,
tRNA, sensitivity to antibiotics
A domain can be divided into kingdoms
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The Three-Domain System
Figure 10.1
3-domain recognizes 3 types of cells. Eukarya includes Kingdoms
Fungi, Plantae, and Animalia, plus certain protists
Peptidoglycan Unusual cell walls
Phylogenetic Hierarchy
Table 10.2
Prokaryotic relationships determined by rRNA sequencing
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Endosymbiotic Theory
Figure 10.3
Figure 10.2
Similarities in rRNA sequences supporting endosymbiotic
theory
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Cummings
Scientific Names
Learning objectives:
Explain why scientific names are used.
Binomials (Genus Species) used by scientists worldwide which
enables them to share knowledge efficiently and accurately
Scientific binomial
Streptococcus pyogenes
Trypanosoma cruzi
Taxonomic Hierarchy
Similar species are grouped into a genus; similar genera are
grouped into a family, etc.
Kids Kingdom
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Cummings
Species Definition
Eukaryotic species:
A group of closely related organisms that breed among
themselves
Prokaryotic species:
Culture: bacteria grown at a give time in media
Clone: Population of cells derived from a single cell
Strain: Genetically different cells within a clone
Viral species:
Population of viruses with similar characteristics that occupies a
particular ecological niche
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Cummings
Domain Eukarya
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; currently being assigned to kingdoms
Viruses not placed in a kingdom (must have host)
Learning objectives: List the major characteristics used to
differentiate the three kingdoms of multicellular Eukarya.
Define protist.
Prokaryotes
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Cummings
References
• Bergey’s Manual of Determinative Bacteriology (for lab
identification) Provides identification schemes for identifying
bacteria and archaea
Morphology, differential staining, biochemical tests, cell wall
composition, oxygen requirements (treatment)
• Bergey’s Manual of Systematic Bacteriology Provides phylogenetic
information on bacteria and archaea
Based on rRNA sequencing
• Approved Lists of Bacterial Names Lists species of known
prokaryotes
Based on published articles
Learning objectives:
Describe how staining and biochemical tests are used to identify
bacteria
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Methods to Classify and Identify Microbes
Morphological characteristics (aided by staining)
Presence of certain enzymes
Phage typing (susceptibility of bacteria to phages)
Fatty acid profiles
Percentage of G-C pairs in nucleic acid
Number and sizes of DNA fragments (fingerprints) produced by
restriction enzymes
Sequence of bases in rRNA
Polymerase chain reaction (PCR) to detect DNA
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Identification Methods
Biochemical tests: Determines presence of bacterial enzymes
Figure 10.8
Morphology and differential staining important to proper treatment
for microbial diseases
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Cummings
Numerical Identification
Figure 10.9
Rapid identification tools for groups of medically important
bacteria (e.g., enterics) are designed to perform several
biochemical tests simultaneously.
The value for each positive test is circled and compared to a
computerized listing.
In this case a confirma-tory test is advised.
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Serology
Slide agglutination
Differentiate Western blotting from Southern blotting.
Explain how serological tests and phage typing can be used to
identify an unknown bacterium.
Left grainy appearance is positive for agglutination – bacteria was
mixed with antibodies produced in response to same strain
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Cummings
Western Blot
Figure 10.12
Proteins separated by electrophoresis can be detected by their
reactions with antibodies
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Cummings
Phage Typing
Figure 10.13
Determining which phages a bacterium is susceptible to:
The tested strain was grown over entire plate; known phages are
placed in different squares; plaques (areas of lysis) appear dark
indicating sensitivity to a specific phage
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Flow Cytometry Uses
Used to identify bacteria in a sample without culturing the
bacteria
Differences in electrical conductivity between species
Fluorescence of some species
Figure 18.11
Genetics
rRNA sequencing
Describe how newly discovered microbe can be classified by: DNA
base composition, rRNA sequencing, DNA fingerprinting, PCR, and
nucleic acid hybridization
Plasmids from 7 different bacteria digested with same restriction
enzyme: none of these bacteria happen to be identical (source of
hospital-acquired infections).
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Cummings
Nucleic Acid Hybridization
Figure 10.15
Greater degree of hybridization (pairing of two strands of DNA,
each from a different microbe) indicates greater similarity
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Nucleic Acid Hybridization: DNA probe
Figure 10.16
Nucleic Acid Hybridization: DNA chip
Figure 10.17
Dichotomous Key
Learning objectives:
Dichotomous key: successive questions with two possible
answers.
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Cummings
Cladogram
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Cummings
Cladogram
Figure 10.5
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