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Introduction
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What are microbes?
Where can they be found?
How big are they?
Fig. 1.7
Types of Microbes
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They include
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Bacteria
Protozoa
Fungi
Algae
*Helminths
*Viruses
*Prions
Bacteria
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Unicellular
Prokaryotic
Cell walls contain peptidoglycan
Have many shapes
Generally reproduce by binary fission
Obtain nourishment from organic or inorganic
substances of photosynthesis
Archaea
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Prokaryotic cells
Cell walls lack peptidoglycan (if present)
Not known to cause human disease
Mainly found in extreme environments
Fungi
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Eukaryotes
May be multicellular or unicellular
May reproduce sexually or asexually
Obtain nourishment by absorbing organic
material from their environments
Cell walls composed of chitin
Protozoa
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Eukaryotes
Unicellular
Classified by type of movement
May live as free entities or parasites
May reproduce sexually or asexually
Algae
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Photosynthetic eukaryotes
May produce sexually or asexually
May be unicellular or multicellular
Cell walls composed of cellulose
Helminths
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Multicellular animal parasites
Viruses
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Acellular organisms
Composed mainly of protein and nucleic
acid; may contain lipids
Obligate intracellular parasites
Prions
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Proteinaceous infectious particles
Composed of protein
6 processes that define life
1.
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growth
reproduction & heredity
metabolism
movement and/or irritability
capacity to transport substances into & out
of cell
cell support, protection & storage
mechanisms
History of Microbiology
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Supernatural
Miasma theory- disease is caused by an
altered chemical in the air
Zaccharias Jansen created the first
microscope (1600). No technology prior to
this
Modification of Microbe Definition
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Thiomargarita nambiensis- large enough to
be seen without a microscope
Viruses and prions- not living organisms
Microbes are easier to study
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Microorganisms are easier to study than
macroorganisms (organisms visible with the
naked eye) because of
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Relative simplicity
Rapid reproduction
Adapatility
History of Microbiology
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Antoni van Leeuwenhoek- discovered
“animalcules”
Robert Hooke- (1678)- developed the
compound microscope; confirmed
Leeuwenhoek’s findings; marked the
beginning of the cell theory
Spontaneous Generation
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Spontaneous generation- theory that living
things arise from nonliving things
Debate of this theory
Francesco Redi
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In his experiment, he used 3 jars containing
meat and left the jar open. He took 3 other
jars containing meat and sealed them. Days
later, only the open jar contained organisms.
Opponents said sealing the jar prevented
fresh air to enter, therefore, microbes could
not grow. He modified his experiment using
a mesh gauze, which was thin enough to
allow air, but prevent microbes.
Fig. 1.p010
John Needham
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Boiled nutrient broth and placed them into
sealed containers. Days later, microbes
grew.
What are some reasons this may have
happened?
Lazarro Spallanzani
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In his experiment, he sealed flasks of nutrient
broth then boiled them. He transferred the
broth into sealed containers and no microbes
grew. Needham suggested the “vital force”
needed for microbes to grow was kept out of
the flask by the seals
Laurent Lavosier
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Showed importance of oxygen to life.
Spallanzani opponents claimed there wasn’t
enough oxygen to support life in his sealed
flasks
Shultz and Schwann
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Thought air was the source of microbes. The
passed air through chemicals into heat
treated flasks. No microbes grew.
Opponents said the chemicals prevented
microbial growth
Louis Pasteur
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Louis Pasteur resolved the debate of spontaneous
generation. He set up flasks with beef broth, boiled
them and left them open. Other flasks containing
boiled beef broth were sealed. A few days later,
microbes were present in the open flasks, but not the
sealed ones. Pasteur suggested that microbes are
present in the air and are capable of contaminating
non living solutions. Then, he set up another series
of flasks with boiled beef broth containing an S
shaped opening. A few days later, no microbes were
present.
Louis Pasteur
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These S shaped flasks allowed air to enter (filling the
oxygen requirement), but prevented microbes from
entering (they are presumably “caught” in the S
shaped openings). He showed microbes are present
in air and can contaminate sterile solutions, but the
air itself does not create microbes. He also showed
these microbes can be destroyed by heat or
microbial access can be blocked. These discoveries
formed the basis of aseptic techniques- techniques
used to prevent microbial contamination
Louis Pasteur
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(1822-1895)
Showed microbes caused
fermentation & spoilage
Disproved spontaneous
generation of m.o.
Developed aseptic
techniques.
Developed a rabies vaccine.
The Golden Age of Microbiology
(1857-1914)
During this time rapid advances in
microbiology were made and spearheaded
by Pasteur and Robert Koch
Were possible due to advances in
microscopy and other technology of the
Industrial Revolution
Germ Theory of Disease
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Many diseases are caused by the growth of
microbes in the body and not by sins, bad
character, or poverty, etc.
Aseptic Techniques
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Ignaz Semmelweis showed that physicians
who do not disinfect their hands can transmit
disease to patients.
Joseph Lister began using phenol as a
disinfectant. The number of deaths from
childbirth fever decreased.
Robert Koch
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Robert Koch (1876) set out to discover the causative
agent of anthrax. He took a sample of blood from
cattle that died of anthrax and cultured it. Samples
from the culture were then injected into healthy
animals. After these animals became sick and died,
he isolated the bacteria in their blood and cultured it.
He found that both sets of organisms were identical.
This experiment established a sequence of steps for
relating a specific organism to a specific disease.
These steps are known as Koch’s postulates
Koch’s Postulates
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1) the same pathogen must be present in every case
of disease
2) pathogen must be isolated from diseased host
and grown in pure culture
3) pathogen from pure culture must cause disease
when inoculated into a healthy susceptible laboratory
animal
4) pathogen must be isolated from inoculated
animal and must be shown to be the original
organism
Robert Koch
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(1843-1910)
Established a sequence of
experimental steps to
show that a specific m.o.
causes a particular
disease.
Developed pure culture
methods.
Identified cause of
anthrax, TB, & cholera.
Edward Jenner
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Edward Jenner (1796) discovered from milkmaids
that those who contracted cowpox became mildly ill,
but never contracted smallpox. Jenner decided to
determine the validity. He obtained permission to
use an 8 year old “volunteer” and inoculated him with
scrapings from cowpox pustules. The child became
ill, but never got smallpox. This process was termed
vaccination. Protection from the disease or recovery
from the disease is called immunity.
Louis Pasteur
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Pasteur (1880) found that aged microbes also confer immunity.
He was working on isolating the causative agent of cholera
using chickens. He inoculated chickens with cholera and they
became sick and died. Allegedly, he went away for the
summer, and his cholera samples aged. When he came back,
he used these aged cultures to inoculate the chickens. These
chickens became mildly ill but did not die. Then (allegedly) he
inoculated these same chickens with a regular strength batch
since he ran out of new chickens. He found that these chickens
did not get sick at all. He determined these aged cultures lost
the ability to cause disease and was able to confer immunity.
Magic Bullet
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Paul Ehrlich (1910) speculated about a
“magic bullet”, a chemical which could
destroy a pathogen without affecting the
host. Prior to this, the only chemical being
used was quinine, to treat malaria. Ehrlich
eventually discovered salvarsan, effective
against syphilis.
Alexander Fleming
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(1928), while doing experiments, left a Petri
dish which became contaminated by mold.
He noted an area of inhibition around the
mold, an area where no bacterial growth
occurred. However, the usefulness of this
mold, used to produce penicillin, did not
occur until the 1940s.
Types of Study
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Bacteriology- study of bacteria
Mycology- study of fungi
Parasitology- study of parasites
Immunology- study of the immune system
Virology- study of viruses
Phycology (algology)- study of algae
Protozoology- study of protozoa
Benefits of Microbes
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Recycle vital elements
Recycle water
Bioremediation
Pest control
Food
Emerging Infectious Disease
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EID’s may occur due to:
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evolutionary changes to existing organisms
spread of diseases to new geographic regions
increased human exposure to new diseases in areas undergoing
ecological change (construction, deforestations)
increased number of patients with depressed immune systems
disruptions in human population, such as crowding or immigration
lack of immunization
lack of nourishment
mass production and packaging of food
animal migration
People Involved in Classification
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Charles Darwin (1859) proposed the theory of
natural selection
Carolus Linnaeus (1735-1759)- divided organisms
into plant and animal and created a 2 name system
Carl von Nageli (1857)- proposed bacteria and fungi
be placed into the plant kingdom
Ernst Haeckel (1866)- proposed kingdom Protista to
include bacteria, protozoa, algae and fungi; Fungi
were placed into their own kingdom in 1959
Robert G. E. Murray (1968)- proposed the kingdom
Prokaryotae
Evolution- living things change
gradually over millions of years
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Changes favoring survival are retained &
less beneficial changes are lost.
All new species originate from preexisting
species.
Closely related organism have similar
features because they evolved from common
ancestral forms.
Evolution usually progresses toward greater
complexity.
Naming micoorganisms
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Binomial (scientific) nomenclature
Gives each microbe 2 names
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Genus - noun, always capitalized
species - adjective, lowercase
Both italicized or underlined
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Staphylococcus aureus (S. aureus)
Bacillus subtilis
(B. subtilis)
Escherichia coli
(E. coli)
More Classification
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Robert Whittaker (1969)- proposed a 5
kingdom system
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Monera (Prokaryotae)- bacteria
Protista-protozoa and algae
Fungi-yeasts, molds
Plantae-plants
Animalia-vertebrates, invertebrates
Carl R. Woese (1978) proposed 3 domains to
be placed above kingdom
Fig. 1.15
Taxonomy - system for organizing,
classifying & naming living things
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Domain - Archaea, Bacteria &
Eukarya
Kingdom - 5
Phylum or Division
Class
Order
Family
Genus
species
3 domains
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Eubacteria -true bacteria, peptidoglycan
Archaea –odd bacteria that live in extreme
environments, high salt, heat, etc
Eukarya- have a nucleus, & organelles
Methods of Classifying and Identifying
Microbes
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Chapter 4 pgs 107-108
Bergey’s Manual of Determinative Bacteriology
Morphological Characteristics
Differential Staining
Biochemical Tests
Serology
DNA base composition
Using rRNA sequencing,
Scientific Method
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Form a hypothesis - a tentative explanation
that can be supported or refuted by
observation & experimentation
A lengthy process of experimentation,
analysis & testing either supports or refutes
the hypothesis.
Results must be published & repeated by
other investigators.
Scientific Method
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If hypothesis is supported by a growing
body of evidence & survives rigorous
scrutiny, it moves to the next level of
confidence - it becomes a theory
Evidence of a theory is so compelling that
the next level of confidence is reached - it
becomes a Law or principle
Fig. 1.11