Topic 1 - BACTERIAL CLASSIFICATION SCHEMES
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Topic contentCharacterisation of speciesBinomial systemProblems of classificationPhylogenetic classification
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Characterisation Why?..Great number and diversity of
organisms.Classification: Grouping of related organism together.Many m/o look alike to be classified
according to the structureLiterally hundreds of bacterial species are
small rods or small cocci.
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Figures 4.1a, 4.2a, 4.2d, 4.4a, 4.4b, 4.4c
Basic ShapesBacillus (rod-shaped) Coccus (spherical)Spiral
SpirillumVibrioSpirochete
Arrangements
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Figure 4.7a
Prokaryotic Cells: ShapesAverage size: 0.2 –1.0 µm 2 – 8 µmMost bacteria are monomorphicA few are pleomorphic
Figure 4.6
The Cell WallPrevents osmotic lysisMade of peptidoglycan (in bacteria)
Gram-Positive Bacterial Cell Wall
Figure 4.13b
Gram-Negative Bacterial Cell Wall
Figure 4.13c
Thick peptidoglycanTeichoic acids
Gram-positiveCell Wall
Figure 4.13b–c
Thin peptidoglycan Outer membrane Periplasmic space
Gram-positiveCell Wall
Motile CellsRotate flagella to run or tumbleMove toward or away from stimuli (taxis)Flagella proteins are H antigens
(e.g., E. coli O157:H7)
Figure 4.7
Arrangements of Bacterial Flagella
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History of Binomial NomenclatureFather of taxonomy?Two name system,Latin scientific name.Formal system of naming organismsOrganizing,classifying and naming organisms
into groups-according to the specific criteria.How to write these names??Vibrio choleraeStaphylococcus spE.coli
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Genus and species Genus - capitalized species – specific epithet.
Example: Escherichia coli,E.coli
• Information gained: shape,who discovered,where it is found,what disease they cause.
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General problemsEstablishing a standard names for organisms
so that we can communicate about themUsually classified according to their
phylogenetic or evolutionary, but not always easy
Leads to introduction of a dichotomous key
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Dichotomous keyHas paired statements describing
characteristic of organismsPaired statement can only have one
statement trueEach paired statement relate to each other
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Figure 10.8
Dichotomous Key
Reasons causing problems1. Deciding what constitutes a species –
because of some bacteria have the similar characteristics so taxonomist try to tolerate the organism within species
2. Deciding what constitutes a kingdom – because most of organism having sexually reproduction so have very factors affecting the variable of the characteristics
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Focusing on bacterial classificationOther organism categorized from domain to
species, but for prokaryotic cell, start from strain to genus
However facing problems reaching the classes and orders level
Wide range of studies needed on identification and building up taxonomy of bacteria
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Phylogenetic hierarchyGrouping organism according to common properties that implies that a group of organisms evolved from common ancestors.
Each species retains some characteristics of the ancestor.
12/04/23 MIC250 by Miss Rashidah Iberahim 26
Hierarchy domain – Bacteriakingdom – none assign for bacteriaphylum – Proteobacteriaclass – Gamma-proteobacteriaorder – Enterobacterialesfamily – Enterobacteriaceagenus – EschericiaSpecies – E.coli
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start
Three domain system classification
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Terminologies (answer)Taxa – subdivisions used to classify organism:
domain, kingdom, phylumPhylogeny / sytematic – the evolutionary
history of a group of organism; phylogenetic relationships are evolutionary relationship
Taxonomy – the science of the classification of organism
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The enD
Short lecture ,but!!!MAKE MORE revision on it….
TQ
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