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MICROBIAL EVOLUTION, SYSTEMATICS AND TAXONOMY

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Title: MICROBIAL EVOLUTION, SYSTEMATICS AND TAXONOMY


1
MICROBIAL EVOLUTION, SYSTEMATICS AND TAXONOMY
  • BY
  • SHEELA
  • M.Sc(Pre.)
    BIOTECHNOLOGY

www.powerpointpresentationon.blogspot.com
2
The Origin and Evolution of Life
  • Life originated more than 3.8 billion years ago
  • All of the compounds necessary for life could
    have formed spontaneously under conditions that
    existed on the early Earth
  • The history of life spans five intervals of
    geologic time

3
Conditions on the Early Earth
  • 4.5 billion years ago
  • Cloud began to condense
  • 4 billion years ago
  • Crust and mantle formed
  • Primitive atmosphere
  • H2, N2, CO, CO2 , probably no O2
  • Hot temperatures

4
STROMOLITES
  • Stromatolites (3.5 bill. Yr)
  • Rocks with distinctive layer structure
  • Look identical to living mats of microbes
  • Layers of microbes and sediment
  • Top layer uses photosynthesis
  • Lower layers use top layers byproducts

5
Early Evolution and Rise of O2
  • First organisms had simple metabolism
  • Atmosphere was O2 free, must have been anaerobic
  • Probably chemoheterotrophs
  • Obtained nutrients from organic material
  • Obtained nutrients from inorganic material
  • Modern archaea appear to be close to the root of
    the tree of life
  • Obtaining energy from chemical reactions
    involving hydrogen, sulfur and iron compounds
    (all abundant on early Earth)

6
Early Evolution
  • Natural selection probably resulted in rapid
    diversification
  • Modern DNA has enzymes that reduce the rate of
    mutations
  • RNA is not so lucky, more likely to have copying
    errors
  • Higher mutation rate in early evolution than now

7
Photosynthesis
  • Most important new metabolic process evolved
    gradually
  • Organisms that lived close to ocean surface
    probably developed means of absorbing sunlight
    (UV in particular)
  • Once absorbed, developed method of turning it
    into energy
  • Modern organisms of purple sulfur bacteria and
    green sulfur bacteria much like early
    photosynthetic microbes, use H2S instead of H2O
    for photosynthesis

8
Photosynthesis
  • Using water for photosynthesis developed later,
    perhaps 3.5 billion years ago
  • First appearing in cyanobacteria (blue-green
    algae)
  • By product of O2, released into atmosphere

9
Rise of O2
  • O2 is highly reactive
  • O2 could not accumulate in atmosphere until
    surface rock was saturated
  • Rocks 2-3 bill. Yr old called banded iron
    formations, show atmosphere had lt1 of current
    amount of O2
  • Rock evidence suggests that O2 amounts in
    atmosphere began to rise about 2.0 bill. Yr ago

10
Origin of Prokaryotic and Eukaryotic Cells
11
Where Did Organelles Come From ?
  • Membranous enclosures
  • Nucleus
  • ER
  • Endosymbiosis
  • Mitochondria
  • Chloroplasts
  • Both have self-replicating DNA, divide
    independently of cell

12
Endosymbiotic Theory
Cyanophora paradoxa
13
Early Eukaryotes
  • Fossil evidence dates to 2.1 bill. Yr ago
  • Dates to when O2 rising in atmosphere
  • DNA evidence suggests that prokaryotes and
    eukaryotes separated from common ancestor much
    earlier
  • O2 played a key role in eukaryote evolution
  • Cells can produce energy more efficiently using
    aerobic metabolism than anaerobic metabolism

14
Primitive Life The RNA World and Molecular
Coding
  • The first life forms may have been
    self-replicating RNAs (RNA life). These were both
    catalytic and informational. Eventually, DNA
    became the genetic repository of cells, and the
    three-part systemDNA, RNA, and proteinbecame
    universal among cells .

15
Possible mechanism of evolution of life
16
Taxonomy Science of classification
  • 1.7 million organisms identified so far
  • All Species Inventory (2001-2025)
  • To identify all species of life on Earth
    (estimated to be 10 100 million)
  • Phylogeny
  • The study of the evolutionary history of organisms

17
Taxonomy
  • Taxonomy - Systematic - is the science of the
    classification of organisms, with the goal of
    showing relationships among organisms.
  • Taxonomy also provides a means of identifying
    organisms.
  • Taxa (Taxon) taxonomic category designed to
    show degrees of similarities among organisms

18
Taxonomy
  • Three major areas of activity
  • Nomenclature naming of organisms
  • Classification the process of ordering of
    organisms in group based on common properties
  • Identification of unknown organisms

19
Nomenclature
  • Every recognized species on earth (at least in
    theory) is given a two-part scientific name. This
    system is called "binomial nomenclature.
  • The scientific name of each species is made up of
    a generic name (generic epithet) and a specific
    name (specific epithet).
  • The genus is the first level of taxonomic
    organization, in a way, because all species that
    are thought to be most closely related, are
    placed together in a genus.
  • Genus is capitalized whole name in italic,
    Latinized

20
Classification
  • 1735 Plant and Animal Kingdoms
  • 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
  • 1968 Kingdom Prokaryotae proposed
  • 1978 Two types of prokaryotic cells found

21
Genetic study in Classification
  • In Genetic - Homologous genes means that the
    genes have similar sequences.
  • In systematic homologous means that genes have a
    common ancestor
  • Orthologs are homologous genes that belong to
    different species but still retain their original
    function
  • Orthologs genes can be used in the construction
    of Phylogenetic trees.
  • The classical example is the 16S ribosomal RNA
    gene

22
16S rRNA
23
The Three-Domain System
24
The Three-Domain System
25
Prokaryotes
  • Historically, prokaryotes were classified on the
    basis of their phenotype.
  • Phenotypic characterization is based on the
    information carried in the products of the genes.
  • Modern characterization is based on the sequence
    of the genes i.e. the genome.
  • This is genetic information and can also tell us
    something about the evolution of the organism.

26
Identification Methods
  • Morphological characteristics
  • Useful for identifying prokaryotes and eukaryotes
  • Differential staining
  • Gram staining, acid-fast staining
  • Cell wall structure
  • Biochemical tests
  • Determine presence of bacterial enzymes,
    metabolic activities
  • Immunological tests
  • Determine antigens
  • toxins
  • Genetic tests
  • Determine presence or structure of genes

27
Ribosomal RNA Sequences as a Tool of Molecular
Evolution
  • Comparative ribosomal RNA sequencing is now a
    routine procedure involving the amplification of
    the gene encoding 16S ribosomal RNA, sequencing
    it, and analyzing the sequence in reference to
    other sequences.

28
Microbial Evolution  Microbial Phylogeny Derived
from Ribosomal RNA Sequences
29
Genetics
  • DNA base composition
  • Guanine cytosine moles (GC)
  • DNA fingerprinting
  • Electrophoresis of restriction enzyme digested
    DNA
  • rRNA sequencing
  • Polymerase Chain Reaction (PCR)

30
Nucleic Acid Hybridization
31
RIBOTYPING
  • Ribotyping is the use of E. Coli rRNA to probe
    chromosomal DNA in southern blot for typing
    bacterial strains. This method is based on the
    fact that the rRNA genes are scattered throughout
    the chromosome of most bacteria and therefore
    polymorphic restriction endonuclease patterns
    result when chromosomes are digested and probe
    with rRNA.

32
THANK YOU
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