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Main Themes of Microbiology
Chapter 1
Copyright © The McGraw-Hill Companies, Inc) Permission required for reproduction or display.
2
Scientific method
• Hypothesis - a conditional explanation that can be verified or falsified (is testable).
Experimental Design
• Independent variable
• Dependent variable
• Controlled conditions
Scientific Theories and Laws Are the Most Important Results of Science
• Scientific theory
• Widely tested
• Supported by extensive evidence
• Accepted by most scientists in a particular area
• Scientific law, law of nature has no known exceptions.
Microbiology Accomplishments
• Cell Theory (Robert Hooke, Antonie van Leeuwenhoek, Theodor Schwann, Matthias Jakob Schleiden)
• Abiogenesis debate (Francesco Redi, Lazzaro Spallanzani, Louis Pasteur, John Tyndall, Ferdinand Cohn)
• Germ Theory of Disease/Sanitation (Louis Pasteur, Robert Koch, Joseph Lister)
• Vaccination (Edward Jenner, Louis Pasteur, Maurice Hillerman)
• Antibiotics ( Paul Ehrlich, Alexander Fleming, Gerhard Domagk, Howard Florey and Ernst Chain)
The Discovery of Microbes
• People have long been aware of the effects of microbial growth
• Spoilage, disease, decomposition
• Microbes are too small to be seen even with hand lenses
• Microscopes changed that
Robert Hooke
• 1665
• English naturalistand architect
• May have been the first to see microorganisms
• Coined the word “cell” to describe what he saw while viewing tree barkfrom a cork oak.
Antonie van Leeuwenhoek
• 1674
• Dutch fabric merchant
• First person to accurately describe living microbes
• Used a simple microscope
• Made and reported many detailed observations
LensSpecimen
holder
Focusscrew
Handle
(a)
(b)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a and inset: © Kathy Park Talaro/Visuals Unlimited; b: © Science VU/Visuals Unlimited
Cell Theory
• Proposed by Theodor Schwann and Matthias Jakob Schleiden in 1839
• States that:
All living things or organisms are made of cells and their products.
New cells are created by old cells dividing into two.
Cells are the basic building units of life.
The Spontaneous Generation Debate
• Biogenesis: living things originate from other living things
• Spontaneous generation (abiogenesis): life rapidly appears from non-living things.
Origins of Abiogenesis
• No distinction between living and non-living in the early human mind
• Aristotle: 400 BC – Favored spontaneous generation
• Concluded that aphids, fleas, flies, and even mice could spontaneously form from other organic materials
Disproval of Abiogenesis
• Francesco Redi (1668) Disproved spontaneous generation of maggots
• Lazzaro Spallanzani (1768) Proved that microorganisms can be killed by boiling
• Nicolas Appert, the father of canning.
Louis Pasteur
• Used swan-necked flasks to disprove abiogenesis conclusively (1859)
• The discovery led to invention of pasteurization and autoclave.
Pasteur’s Experiment
Microbesbeingdestroyed
Vigorous heatis applied.
Broth free oflive cells (sterile)
Neck intact; airbornemicrobes are
trapped at base,and broth is sterile.
Neck on secondsterile flaskis broken;
growth occurs.
Discovery of Endospores
• John Tyndall (1876)
• Described heat-resistant microbes from hay infusions
• Used discontinuous heating used to sterilize (tyndalization)
• Ferdinand Cohn (1876)
• Discovered and described endospores in some soil bacteria (Bacillus)
Germ Theory of Disease
• Epidemics caused by miasma, a noxious form of "bad air"
• John Snow (1849) tied cholera outbreak to a contaminated water source
Germ Theory of Disease
• Louis Pasteur – showed that silkworm disease was caused by a protozoan parasite
• Robert Koch – proved that a specific bacteria caused a specific disease - linked Bacillus anthracis to anthrax in cattle; described several postulates for proving the etiological (causative) agent of disease (1884)
Koch’s Postulates
• A specific microorganism causes an infectious disease
• Isolate microorganism
• Infection with pure microbe results in disease
• Re-isolate microorganism from infected individual
Development of Aseptic Techniques
• Ignaz Semmelweiss (1847)– proposed that surgeons wash their hands with chlorinated lime solution to prevent transmission of childbirth fever
• Joseph Lister (1870s) – introduced aseptic techniques; used carbolic acid (phenol) to clean hands, wounds and operating rooms to reduce the number of post-operative infections.
Vaccination
• The earliest documented examples of vaccination from India and China (17th century), to protect against the small pox
• The Anatolian Ottoman Turks used inoculation of small pox scab matter to protect against the disease.
• Edward Jenner (1796), the “father” of vaccination
• Luis Pasteur developed killed vaccines to protect against anthrax and rabies
• Maurice Ralph Hilleman developed 36 vaccines.
Recent Developments in Technology
• Restriction Enzymes
• Polymerase Chain Reaction (PCR)
• Biofilms
• Small RNAs
Microbial Classification
• Taxonomy is the science of classifying living things. Taxa (singular: taxon) categories that show the degree of similarity between organisms
• Systematics or Phylogeny is the study of the evolutionary history of organisms.
• Nomenclature naming living organisms.
• Identification studying of traits of a specific organism in order to put it into a specific group
The Five Kingdom
Model
EU
KA
RY
OT
ES
PR
OK
AR
YO
TE
S
Seed plants
First eukaryoticcells appeared 2 billion years ago.
(Protista)PROTISTS
First multicellularorganisms appeared 0.6 billion years ago.
Sponges
Flatworms
Nematodes
Echinoderms
ChordatesArthropods
Annelids
Mollusks
ANIMALS(Animalia)
Molds
Clubfungi
Yeasts
(Myceteae)FUNGI
Ciliates
Amoebas
Flagellates
Apicomplexans
Early eukaryotes
Bacteria
First cells appeared3–4 billion years ago.
Earliest cell2 cell types5 kingdoms
Archaea
MONERA
Dinoflagellates
Diatoms
Brownalgae
Redalgae
Green algae
Slimemolds
(Plantae)PLANTS
Ferns
Angiosperms
Gymnosperms
Mosses
Robert Whittaker (1959)
Taxonomy
• Kingdom Kings
• Phylum Play
• Class Chess
• Order On
• Family Fine
• Genus Green
• Species Satin
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominoidea
Genus: Homo
Species: sapiens
Kingdom: Protistaincludes protozoa and algae
Phylum: Ciliophoraonly protozoawith cilia
Class: HymenostomeaSingle cells withregular rows ofcilia; rapid swimmers
Order: HymenostomatidaElongate oval cells withcilia in the oral cavity
Family: ParameciidaeCells rotate while swimmingand have oral grooves.
Genus: ParameciumPointed, cigar-shaped cells withmacronuclei and micronuclei
Species: Caudatum Cells cylindrical, long and pointed at one end
()
Domain: Eukarya (All eukaryotic organisms)
Domain: Eukarya (All eukaryotic organisms)
Lemur
Sea starSea squirt
New Views of Phylogeny
• Based on 16S RNA sequence
Domain Bacteria Domain Archaea Domain Eukarya
Cyanobacteria
ChlamydiasSpirochetes
Gram-positivebacteria
Endosporeproducers
Gram-negativebacteria
Methaneproducers
Prokaryotesthat live inextreme salt
Prokaryotesthat live inextreme heat
Eukaryotes
Ancestral Cell Line (first living cells)
Nomenclature
• Designed by Carilus Linnaeus
• Every organism has a two-name (binomial) designation – Genus species
• Note italics and the capitalization!
Conclusions:
• The scientific method is a process of observation, hypothesis generation, data collection, analysis of results, and dissemination of findings. Proper experimental design, repetition of measurements or experiments is critical if one is to determine the validity of findings.
• Scientific theories are thoroughly tested before being accepted. They can be modified after being accepted.
• The major accomplishments of microbiology are: Cell Theory, disproval of abiogenesis, germ theory of disease and invention of sanitation, discovery of vaccination and antibiotics.
Conclusions:
• The five kingdom model of classification of the living world is based on structural similarities, cellular organization, and nutritional type, and it includes Monera (Bacteria and Archaebacteria), Protists, Plants, Fungi, and Animals.
• The taxonomic categories from top to bottom are: kingdom, philum, class, order, family, genus and species.
• The Woese-Fox phylogenetic system is based on the similarity of 16S RNA sequence, and includes domains Bacteria, Archea and Eucarya