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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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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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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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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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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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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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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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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Western Blot
Figure 10.12
Proteins separated by electrophoresis can be detected by their reactions with antibodies
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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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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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Cladogram
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Cladogram
Figure 10.5