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Chapter 1
The Microbial
World and You
© 2013 Pearson Education, Inc.
Copyright © 2013 Pearson Education, Inc.
Lectures prepared by Christine L. Case
Lectures prepared by Christine L. Case
© 2013 Pearson Education, Inc.
Microbes in Our Lives
 Microorganisms are organisms that are too small to
be seen with the unaided eye
 Have to use microscopes to see them
 Germ refers to a rapidly growing cell
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Microbes in Our Lives
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Decompose organic waste
The food chain for the oceans, lakes and rivers.
Photosynthetic
Produce industrial chemicals such as ethanol
and acetone
 Aid in digestion of food and vitamin synthesis
 Produce fermented foods such as pickles, soy
sauce, vinegar, cheese, and bread
 Produce products used in manufacturing
(e.g., cellulase) and disease treatment (e.g., insulin)
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Designer Jeans: Made by Microbes?
 Stone-washing: Trichoderma
 Indigo: E. coli
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Microbes in Our Lives
 Knowledge of microorganisms allows humans to
 Prevent food spoilage
 Prevent disease occurrence
 Led to aseptic techniques to prevent contamination
in medicine and in microbiology laboratories
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Naming and Classifying Microorganisms
 Carolus Linnaeus established the system of
scientific nomenclature
 Each organism has two names: the genus and
species
 Genus is ALWAYS capitalized.
 species is ALWAYS lower case.
 Both words have to either be in ITALICS or
UNDERLINED.
 Examples:
1. Staphylococcus aureus, S. aureus
2. Streptococcus pyogenes, S. pyogenes
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Scientific Names
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Which is a correct scientific name?
a. Baker’s yeast
b. Saccharomyces cerevisiae
c. Saccharomyces cerevisiae
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Types of Microorganisms
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Bacteria
Archaea
Fungi
Protozoa
Algae
Viruses
Helminths
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Figure 1.1 Types of microorganisms.
Sporangia
Bacteria
Prey
Pseudopods
CD4+ T cell
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HIVs
Bacteria
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Prokaryotes- no nucleus
Peptidoglycan cell walls
Binary fission- 1 parent cell  2 daughter cells
For energy, use organic chemicals, inorganic
chemicals, or photosynthesis
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Figure 1.1a Types of microorganisms.
Bacteria
(a) The rod-shaped bacterium Haemophilus influenzae,
one of the bacterial causes of pneumonia.
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Archaea
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Prokaryotic
Lack peptidoglycan in cell walls
Live in extreme environments
Include:
 Methanogens
 Extreme halophiles
 Extreme thermophiles
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Figure 4.5b Star-shaped and rectangular prokaryotes.
Rectangular bacteria
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Fungi
 Eukaryotes
 Chitin cell walls
 Use organic chemicals for energy
 Types:
1. Molds and mushrooms are multicellular,
which are composed of filaments called hyphae
2. Yeasts are unicellular
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Figure 1.1b Types of microorganisms.
Sporangia
(b) Mucor, a common bread mold, is a type of fungus.
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Protozoa
 Eukaryotes- has nucleus
 Absorb or ingest organic chemicals
 May be motile via pseudopods, cilia, or flagella
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Figure 1.1c Types of microorganisms.
Prey
Pseudopods
(c) An ameba, a protozoan, approaching a food particle.
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Algae
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Eukaryotes
Cellulose cell walls
Use photosynthesis for energy
Produce molecular oxygen and organic compounds
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Figure 1.1d Types of microorganisms.
(d) The pond alga Volvox.
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Viruses
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Acellular- tiny particles
Consist of DNA or RNA core
Core is surrounded by a protein coat
Coat may be enclosed in a lipid envelope
Are replicated only when they are in a living host cell
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Figure 1.1e Types of microorganisms.
CD4+ T cell
HIVs
(e) Several human immunodeficiency viruses (HIVs), the
causative agent of AIDS, budding from a CD4+ T cell.
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Helminths
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Eukaryotes
Multicellular animals
Parasitic flatworms and roundworms
Microscopic stages in life cycles
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Figure 1.6 Parasitology: the study of protozoa and parasitic worms.
Rod of
Asclepius,
symbol of the
medical
profession.
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A parasitic guinea worm (Dracunculus medinensis)
is removed from the subcutaneous tissue of a patient
by winding it onto a stick. This procedure may have
been used for the design of the symbol in part (a).
Classification of Microorganisms
 Three domains
 Bacteria
 Archaea
 Eukarya
 Protists
 Fungi
 Plants
 Animals
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Figure 10.1 The Three-Domain System.
Eukarya
Bacteria
Origin of chloroplasts
Animals
Fungi
Origin of mitochondria
Amebae
Mitochondria
Slime molds
Cyanobacteria
Proteobacteria
Chloroplasts
Archaea
Plants
Extreme
halophiles
Methanogens
Ciliates
Green
algae
Dinoflagellates
Diatoms
Hyperthermophiles
Gram-positive
bacteria
Euglenozoa
Giardia
Thermotoga
Horizontal gene transfer
occurred within the
community of early cells.
Mitochondrion degenerates
Nucleoplasm grows larger
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A Brief History of Microbiology
 Ancestors of bacteria were the first life on Earth
 The first microbes were observed in 1673
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The First Observations
 1665: Robert Hooke reported that living things are
composed of little boxes, or cells
 1673–1723: Anton van Leeuwenhoek described live
microorganisms
 1858: Rudolf Virchow said cells arise from
preexisting cells
 Cell theory: All living things are composed of cells and
come from preexisting cells
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Figure 1.2b Anton van Leeuwenhoek’s microscopic observations.
Lens
Location of specimen
on pin
Specimen-positioning
screw
Focusing control
Stage-positioning screw
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Microscope replica
The Debate over Spontaneous
Generation
 Spontaneous generation: the hypothesis that living
organisms arise from nonliving matter;
a “vital force” forms life
 Biogenesis: the hypothesis that living organisms
arise from preexisting life
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Evidence Pro and Con
 1668: Francesco Redi filled 6 jars with
decaying meat
Conditions
Results
Three jars covered with fine net
No maggots
Three open jars
Maggots appeared
From where did the maggots come?
What was the purpose of the sealed jars?
Spontaneous generation or biogenesis?
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Evidence Pro and Con
 1745: John Needham put boiled nutrient broth into
covered flasks
Conditions
Results
Nutrient broth heated, then placed Microbial growth
in sealed flask
From where did the microbes come?
Spontaneous generation or biogenesis?
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Evidence Pro and Con
 1765: Lazzaro Spallanzani boiled nutrient solutions
in flasks
Conditions
Results
Nutrient broth placed in flask,
heated, then sealed
No microbial growth
Spontaneous generation or biogenesis?
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Evidence Pro and Con
 1861: Louis Pasteur demonstrated that
microorganisms are present in the air
Conditions
Results
Nutrient broth placed in flask,
heated, NOT sealed
Microbial growth
Nutrient broth placed in flask,
heated, then sealed
No microbial growth
Spontaneous generation or biogenesis?
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Figure 1.3 Disproving the Theory of Spontaneous Generation.
Pasteur first poured
beef broth into a
long-necked flask.
Next he heated the neck
of the flask and bent it
into an S-shape; then he
boiled the broth for
several minutes.
Microorganisms did not
appear in the cooled solution,
even after long periods.
Bend prevented microbes
from entering the flask.
Microorganisms were
present in the broth.
Microorganisms were not
present in the broth after
boiling.
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Microorganisms were
not present even after
long periods.
The Golden Age of Microbiology
 1857–1914
 Beginning with Pasteur’s work, discoveries included
the relationship between microbes and disease,
immunity, and antimicrobial drugs
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Fermentation and Pasteurization
 Pasteur showed that microbes are responsible for
fermentation
 Fermentation is the conversion of sugar to alcohol to
make beer and wine
 Pasteur showed microbial growth is also responsible
for spoilage of food
 Pasteur demonstrated that spoilage bacteria could be
killed by heat
 Pasteurization is the application of a high heat for a short
time
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The Germ Theory of Disease
 1840s: Ignaz Semmelweis advocated handwashing
to prevent transmission of puerperal fever from one
obstetrical patient to another
 1860s: Applying Pasteur’s work showing microbes
are in the air, can spoil food, and cause animal
diseases, Joseph Lister used a chemical disinfectant
to prevent surgical wound infections
 1876: Robert Koch proved that a bacterium
causes anthrax and provided the experimental
steps, Koch’s postulates, to prove that a specific
microbe causes a specific disease
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Koch’s Postulates
1. Take a specimen from a sick person.
2. Grow it out on media.
3. Inoculate a healthy person with the specimen from
the media.
4. When person demonstrates disease symptoms,
take a specimen from him/her and grow it on
media.
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Vaccination
 1796: Edward Jenner inoculated a person with
cowpox virus, who was then protected from smallpox
 Vaccination is derived from vacca, for cow
 Immunity- protection given from a vaccine
 First time a living virus was use to produce immunity
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The Birth of Modern Chemotherapy
 Chemotherapy- treatment of a disease with
chemicals
 Types:
1. Synthetic Drugs- prepared from chemicals in a lab
2. Antibiotics- chemicals produced by bacteria and
fungi that inhibit or kill other microbes
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The First Synthetic Drugs
 Paul Ehrlich- speculated about a “magic bullet”
that could destroy a pathogen without harming the
host
 1910: Ehrlich developed a synthetic arsenic drug,
salvarsan, to treat syphilis
 1930s: Sulfonamides(made from dyes) were synthesized
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A Fortunate Accident—Antibiotics
 1928: Alexander
Fleming discovered the
first antibiotic
 Fleming observed that
Penicillium fungus
made an antibiotic,
penicillin, that killed S.
aureus
 1940s: Penicillin was
tested clinically and
mass produced
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Modern Developments in Microbiology
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Bacteriology- study of bacteria
Mycology- study of fungi
Virology- study of viruses
Parasitology- study of protozoa and parasitic
worms (helminths)
 Immunology- study of immunity
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Recombinant DNA Technology
 Microbial genetics: the study of how microbes
inherit traits
 Molecular biology: the study of how DNA directs
protein synthesis
 Genomics: the study of an organism’s genes; has
provided new tools for classifying microorganisms
 Recombinant DNA: DNA made from two different
sources
 In the 1960s, Paul Berg inserted animal DNA into bacterial
DNA, and the bacteria produced an animal protein
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Biotechnology
 Recombinant DNA technology, a new technique
for biotechnology, enables bacteria and fungi to
produce a variety of proteins, including vaccines and
enzymes
 Missing or defective genes in human cells can be replaced
in gene therapy
 Genetically modified bacteria are used to protect crops
from insects and from freezing
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Microbial Ecology
 Studies the relationship between bacteria and
plants/animals
 Bacteria recycle carbon, nutrients, sulfur, and phosphorus
that can be used by plants and animals
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Bioremediation
 Bacteria degrade organic matter in sewage
 Bacteria degrade or detoxify pollutants such as oil
and mercury
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Figure 27.10 Composting municipal wastes.
Solid municipal wastes being turned by a specially designed machine
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Biological Insecticides
 Microbes that are
pathogenic to insects
are alternatives to
chemical pesticides in
preventing insect
damage to agricultural
crops and disease
transmission
 Bacillus thuringiensisfatal in many insects but
harmless to other
animals, including
humans, and to plants
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Biotechnology
 Biotechnology, the use of microbes to produce
foods and chemicals, is centuries old
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Figure 28.8 Making cheddar cheese.
The milk has been coagulated by the
action of rennin (forming curd) and is
inoculated with ripening bacteria for
flavor and acidity. Here the workers are
cutting the curd into slabs.
The curd is chopped into small cubes to
facilitate efficient draining of whey.
The curd is milled to allow even more
drainage of whey and is compressed into
blocks for extended ripening. The longer the
ripening, the more acidic (sharper) the cheese.
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Normal Microbiota
 Bacteria were once classified as plants, giving rise to
use of the term flora for microbes
 This term has been replaced by microbiota
 Microbes normally present in and on the human
body are called normal microbiota
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Figure 1.7 Several types of bacteria found as part of the normal microbiota on the surface of the human tongue.
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Normal Microbiota
 Prevent growth of pathogens
 Produce growth factors, such as folic acid and
vitamin K
 Resistance is the ability of the body to ward off
disease
 Resistance factors include skin, stomach acid, and
antimicrobial chemicals
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Biofilms
 Microbes attach to solid surfaces and grow into
masses
 They will grow on rocks, pipes, teeth, and medical
implants
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Figure 1.8 Biofilm on a catheter.
Staphylococcus
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Infectious Diseases
 When a pathogen overcomes the host’s resistance,
disease results
 “ It is time to close the book on infectious diseases, the
war against pestilence is over.”- Luther Terry, 1964
Surgeon General of the US
 “ Infectious diseases a rising peril; Death rates in US up
58% since 1980.”- David Satcher, 1999 Surgeon General
of the US
 Emerging infectious diseases (EIDs): new
diseases and diseases increasing in incidence
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What changed since the 1960s?
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Organisms have changed or adapted.
People are living longer.
Population is more mobile.
Emerging diseases and Reemerging diseases.
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H1N1 influenza
 Swine flu
 Seen in the US for the
first time in April 2009
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Avian Influenza A
 Influenza A virus
 Primarily in waterfowl
and poultry
 Sustained human-tohuman transmission
has not occurred yet
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MRSA
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Methicillin-resistant Staphylococcus aureus
1950s: Penicillin resistance developed
1980s: Methicillin resistance
1990s: MRSA resistance to vancomycin reported
 VRSA: vancomycin-resistant S. aureus
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West Nile Encephalitis
 Caused by West Nile
virus
 First diagnosed in the
West Nile region of
Uganda
in 1937
 Appeared in New York
City in 1999
 In nonmigratory birds
in 47 states
 September 2012- 172
cases in MS
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Bovine Spongiform Encephalopathy
 Caused by a prion
 Also causes
Creutzfeldt-Jakob
disease (CJD)
 New variant CJD in
humans is related to
cattle that have been
fed sheep offal for
protein
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Escherichia coli O157:H7
 Toxin-producing strain
of E. coli
 First seen in 1982
 Leading cause of
diarrhea worldwide
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Cryptosporidiosis
 Cryptosporidium
protozoa
 First reported in 1976
 Causes 30% of
diarrheal illness in
developing countries
 In the United States,
transmitted via water
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Acquired immunodeficiency syndrome
(AIDS)
 Caused by human immunodeficiency virus (HIV)
 First identified in 1981
 Worldwide epidemic infecting 33 million people;
7500 new infections every day
 Sexually transmitted infection affecting males and
females
 HIV/AIDS in the United States: 26% are female, and
49% are African American
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