Transcript What is a Microbe?

In the Name of GOD
What is a Microbe?
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They are the oldest form of life on earth. Microbe
fossils date back more than 3.5 billion years to a time
when the Earth was covered with oceans that regularly
reached the boiling point, hundreds of millions of years
before dinosaurs roamed the earth.
Without microbes, we couldn’t eat or breathe.
Without us, they’d probably be just fine.
Understanding microbes is vital to understanding the
past and the future of ourselves and our planet.
Microbiology
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Microbiology is the study of living
microorganisms (microbes) , simple in structure,
and usually small in size, include bacteria, algae,
fungi, protozoa, and viruses.
Pure microbiology
Applied microbiology
Medical Microbiology
The study of relationships
between humans and
microbes, including:
- Infection
- Infective disease
- Colonisation
- Transmission of infective
agents
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Development of microscopy
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1590: Hans and Zacharias Janssen (Dutch lens
grinders) mounted two lenses in a tube to
produce the first compound microscope.
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1660: Robert Hooke (1635-1703) published
"Micrographia", containing drawings and
detailed observations of biological materials
made with the best compound microscope and
illumination system of the time.
Development of microscopy
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1676: Anton van Leeuwenhoek
(1632-1723) was the first person
to observe microorganisms.
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1883: Carl Zeiss and Ernst Abbe
pioneered developments in
microscopy (such as immersion
lenses and apochromatic lenses
which reduce chromatic
aberration) which persist until
the present day.
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1931: Ernst Ruska constructed
the first electron microscope.
The History of Microbiology
Timeline
____1600_______1700_______ 1800_________ 1900_______2000 ____
1677
Observed "little animals" (Antony
Leeuwenhoek)
 1796
First scientific Small pox vaccination
(Edward Jenner)
 1850
Advocated washing hands to stop the
spread of disease (Ignaz Semmelweis)
 1861
Disproved spontaneous generation
(Louis Pasteur)
 1862
Supported Germ Theory of Disease
(Louis Pasteur)
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The History of Microbiology
1867
Practiced antiseptic surgery (Joseph
Lister)
 1876
First proof of Germ Theory of
Disease with B. anthracis discovery
(Robert Koch)
 1881
Growth of Bacteria on solid media
(Robert Koch)
 1882
Outlined Kochs postulates (Robert
Koch)
 1882
Developed acid-fast Stain (Paul
Ehrlich)
 1884
Developed Gram Stain (Christian
Gram)
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The History of Microbiology
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1885
First Rabies vaccination (Louis
Pasteur)
1887
Invented Petri Dish (R.J. Petri)
1892
Discovered viruses (Dmitri
Iosifovich Ivanovski)
1899
Recognized viral dependence on
cells for reproduction (Martinus
Beijerinck)
1900
Proved mosquitoes carried the
yellow fever agent (Walter Reed)
The History of Microbiology
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1910
Discovered cure for syphilis (Paul Ehrlich)
1928
Discovered Penicillin (Alexander Fleming)
1977
Developed a method to sequence DNA (W.
Gilbert & F. Sanger)
1983
Polymerase Chain Reaction invented (Kary
Mullis)
1995
First microbial genomic sequence published
(H. influenzae) (TIGR)
2003
Complete sequence of human genome was
published
Spontaneous generation controversy:
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Aristotle (384-322) and others believed that living
organisms could develop from non-living materials.
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1688: Francesco Redi (1626-1697) was an Italian physician
who refuted the idea of spontaneous generation by
showing that rotting meat carefully kept from flies will not
spontaneously produce maggots.
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1836: Theodor Schwann (1810-1882) passed air through
red hot tubes and observed no growth , and helped
develop the cell theory of living organisms, namely that all
living organisms are composed of one or more cells and
that the cell is the basic functional unit of living
organisms.
Spontaneous generation controversy:
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1861: Louis Pasteur's (18221895) famous experiments
with swan-necked flasks
finally proved that
microorganisms do not arise
by spontaneous generation.
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John Tyndall (1820-1893)
proved that dust carried
germs.
Proof that microbes cause disease
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1546: Hieronymus Fracastorius (Girolamo Fracastoro) wrote
"On Contagion" ("De contagione et contagiosis morbis et
curatione"), the first known discussion of the phenomenon of
contagious infection.
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1835 Agostino Bassi de Lodi showed that a disease affecting
silkworms was caused by a fungus - the first microorganism to
be recognized as a contagious agent of animal disease.
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1847: Ignaz Semmelweiss (1818-1865), a Hungarian physician
who decided that doctors in Vienna hospitals were spreading
childbed fever while delivering babies. He started forcing
doctors under his supervision to wash their hands before
touching patients.
Proof that microbes cause disease
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Friedrich Henle proposed criteria for providing that
microorganisms were responsible for causing human disease
(the germ theory of disease) in 1840.
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1857: Louis Pasteur proposed the "germ theory" of disease.
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1867: Joseph Lister (1827-1912) introduced antiseptics in
surgery. By spraying carbolic acid on surgical instruments,
wounds and dressings, he reduced surgical mortality due to
bacterial infection considerably.
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1878: Joseph Lister developed the first pure culture
techniques. He made serial dilutions in liquid media to obtain
Bacterium ( Lactobacillus) lactis.
Proof that microbes cause disease
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1876: Robert Koch (1843-1910).
German bacteriologist was the first
to cultivate anthrax bacteria outside
the body using blood serum at body
temperature. Building on pasteur's
"germ theory", he subsequently
published "Koch's postulates"
(1884), the critical test for the
involvement of a microorganism in a
disease:
1-The agent must be present in
every case of the disease.
2-The agent must be isolated and
cultured in vitro.
3-The disease must be reproduced
when a pure culture of the agent is
inoculated into a susceptible host.
4-The agent must be recoverable
from the experimentally-infected
host
Procaryote: primitive nucleus
Procaryotes include the Eubacteria (true bacteria) and archaebacteria
(ancient bacteria)
Phylogenetic tree of life
Prokaryotes and eukaryotes
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Strain: progeny and subcultures of a single colony
isolate in pure culture.
Species: a collection of strains that share many
features in common and differ considerably from
other strains.
1- structural traits of shape, size mode of movement,
resting stage, Gram strain reaction, macroscopic
growth
2- biochemical and nutritional traits, end products,
3- physiologic traits relative to oxygen, temperature,
pH, response to antimicrobial agents
4- ecologic traits
5- DNA base composition, homology, genetic traits
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Species biotype (biovar): within a species
collection or cluster, a strain that is chosen
arbitrarily to best represent that species .
Biotype strains are used as reference strains
Serotype( serovar)
Pathotype (pathovar)
Morphotype (morphovars)
Phage type (phagovar)
Taxonomy and nomenclature of bacteria
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Microbes observed earlier by van Leeuwenhoek,
were assigned to 6 species in the class chaos by
Linnaeus.
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Otto Muller organized bacteria in to genera and
species according to classification methods of
Carolus Linnaeus in 1770s. ( beginning of the
taxonomic classification of microbes)
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Cohn classified bacteria. (1872)
Taxonomy and nomenclature of bacteria
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Important landmarks in the advance of bacterial
taxonomy were classification of Chester (1901),OrhaJensen(1919) and Buchanan(1919-1925)
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Committee of bacterial and viral taxonomy (Murphy 1995)
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ICSB regularly providing lists of resent validly
published species names and proposed changes in
nomenclature first in the “international journal of
systematic and evolutionary microbiology” (IJSEM)
Taxonomy and nomenclature of bacteria
The status of microbial scheme is reviewed about
every 10 years in successive editions of
“Bergey`s manual of systematic bacteriology “
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Recent advice on characterization
methodologies and the definition of the species
level is presented by Stackebrandt et al.(2002) “
species should be based on the description of
more than one and preferably at least to 10
strains.
Classification of bacteria
(Bergey`s manual of systematic bacteriology)
Kingdom procaryotae :
1- Gracillicutes (Gram- bacteria)
2- Firmicutes (Gram+ bacteria)
3- Tenericutes (cell wall-less bacteria: Mycoplasma
/ Mollicutes)
4- Mendosicutes (Archaebacteria)
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Numerical identification
Based on surveys that
define tables of the
expected frequency of
positively in a series of
tests for each species.”
Unknown” isolate
compare with this table.
Bacterial classification
1- Phenotypic classification
of bacteria
 Microscopic morphology
 Colonial morphology
 Biochemical tests
 Biotyping
 Serotyping
 Antibiogram patterns
 Phage typing
Bacterial classification
2- Analytic classification of bacteria
 Cell wall fatty-acid analysis
 Whole cell analysis
 SDS-PAGE* analysis of proteins (fingerprinting)
 Multifocus locus enzyme electrophoresis
*sodium doddecyl sulfate polyacrylamide gel electrophoresis
Bacterial classification
3- Genotypic classification of bacteria
 Guanine - cytosine ratio to adenine-thymidine in DNA (detect
heterogeneity at genus level-25%-75%). S.aureus: %32-%36; E.coli,
shigella,salmonell:48%-53%;M.tubeculosis :62%-70%
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DNA-DNA hybridization techniques (comparison of base sequence
compatibility between strains)- > 70% binding and <5% difference = in
same species; E.coli100%; B.subtilis1%; p.aeruginosa : %1-3%
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Nucleic acid sequence analysis (i.e. rRNA sequencing) E.coli:100%;
B.fragilis: 72%
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Plasmid analysis
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Ribotyping
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Chromosomal DNA fragment analysis