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CHAPTER
1
The Microbial
World and You
© 2016 Pearson Education, Inc.
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Microbes in Our Lives
Learning Objective
1-1 List several ways in which microbes affect our
lives.
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Microbes in Our Lives
• Microorganisms are organisms that are too small
to be seen with the unaided eye
• Microbes include bacteria, fungi, protozoa,
microscopic algae, and viruses
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Microbes in Our Lives
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A few are pathogenic (disease-producing)
Decompose organic waste
Generate oxygen by photosynthesis
Produce chemical products such as ethanol,
acetone, and vitamins
• Produce fermented foods such as 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?
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Denim fading: Trichoderma
Cotton production: Gluconacetobacter
Bleaching: mushroom peroxidase
Indigo: Escherichia coli
Plastic: bacterial polyhydroxyalkanoate
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Applications of Microbiology 1.1
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Applications of Microbiology 1.2
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Microbes in Our Lives
• Knowledge of microorganisms allows humans to
• Prevent food spoilage
• Prevent disease
• Understand causes and transmission of disease to
prevent epidemics
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Check Your Understanding
 Describe some of the destructive and beneficial
actions of microbes.
1-1
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Naming and Classifying Microorganisms
Learning Objectives
1-2 Recognize the system of scientific
nomenclature that uses two names: a genus
and a specific epithet.
1-3 Differentiate the major characteristics of each
group of microorganisms.
1-4 List the three domains.
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Naming and Classifying Microorganisms
• Carolus Linnaeus established the system of
scientific nomenclature in 1735
• Each organism has two names: the genus and the
specific epithet
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Nomenclature
• Scientific names
• Are italicized or underlined
• The genus is capitalized; the specific epithet is lowercase
• Are "Latinized" and used worldwide
• May be descriptive or honor a scientist
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Nomenclature
• Escherichia coli
• Honors the discoverer, Theodor Escherich
• Describes the bacterium's habitat—the large intestine,
or colon
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Nomenclature
• Staphylococcus aureus
• Describes the clustered (staphylo-) spherical
(coccus) cells
• Describes the gold-colored (aureus) colonies
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Nomenclature
• After the first use, scientific names may be
abbreviated with the first letter of the genus and
the specific epithet:
• Escherichia coli and Staphylococcus aureus are found
in the human body
• E. coli is found in the large intestine, and S. aureus is on
skin
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Check Your Understanding
 Distinguish a genus from a specific epithet.
1-2
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Types of Microorganisms
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Bacteria
Archaea
Fungi
Protozoa
Algae
Viruses
Multicellular Animal Parasites
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Figure 1.1 Types of microorganisms.
Bacteria
Sporangia
Food
particle
Pseudopod
CD4 + T cell
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HIVs
Bacteria
• Prokaryotes
• ”Prenucleus"
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Single-celled
Peptidoglycan cell walls
Divide via binary fission
Derive nutrition from organic or inorganic
chemicals or photosynthesis
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Figure 1.1a Types of microorganisms.
Bacteria
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Archaea
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Prokaryotes
Lack peptidoglycan cell walls
Often live in extreme environments
Include:
• Methanogens
• Extreme halophiles
• Extreme thermophiles
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Fungi
• Eukaryotes
• Distinct nucleus
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Chitin cell walls
Absorb organic chemicals for energy
Yeasts are unicellular
Molds and mushrooms are multicellular
• Molds consist of masses of mycelia, which are
composed of filaments called hyphae
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Figure 1.1b Types of microorganisms.
Sporangia
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Protozoa
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Eukaryotes
Absorb or ingest organic chemicals
May be motile via pseudopods, cilia, or flagella
Free-living or parasitic (derive nutrients from a
living host)
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Figure 1.1c Types of microorganisms.
Food
particle
Pseudopod
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Algae
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Eukaryotes
Cellulose cell walls
Found in freshwater, saltwater, and soil
Use photosynthesis for energy
Produce oxygen and carbohydrates
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Figure 1.1d Types of microorganisms.
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Viruses
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Acellular
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
• Inert outside living hosts
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Figure 1.1e Types of microorganisms.
CD4 + T cell
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HIVs
Multicellular Animal Parasites
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Eukaryotes
Multicellular animals
Not strictly microorganisms
Parasitic flatworms and roundworms are called
helminths
• Some microscopic stages in their life cycles
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Check Your Understanding
 Which groups of microbes are prokaryotes?
Which are eukaryotes?
1-3
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Classification of Microorganisms
• Developed by Carl Woese
• Three domains based on cellular organization
• Bacteria
• Archaea
• Eukarya
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Protists
Fungi
Plants
Animals
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Figure 10.1 Three-Domain System.
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Check Your Understanding
 What are the three domains?
1-4
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A Brief History of Microbiology
Learning Objectives
1-5 Explain the importance of observations made
by Hooke and van Leeuwenhoek.
1-6 Compare spontaneous generation and
biogenesis.
1-7 Identify the contributions to microbiology made
by Needham, Spallanzani, Virchow, and
Pasteur.
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The First Observations
• 1665: Robert Hooke reported that living things are
composed of little boxes, or "cells"
• Marked the beginning of cell theory: All living things are
composed of cells
• The first microbes were observed from 1623–1673
by Anton van Leeuwenhoek
• "Animalcules" viewed through magnifying lenses
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Figure 1.2b Anton van Leeuwenhoek's microscopic observations.
Lens
Location of
specimen on pin
Specimenpositioning screw
Focusing control
Stagepositioning screw
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Microscope replica
Check Your Understanding
 What is the cell theory?
1-5
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The Debate over Spontaneous Generation
• Spontaneous generation: the hypothesis that life
arises from nonliving matter; a "vital force" is
necessary for life
• Biogenesis: the hypothesis that living cells arise
only from preexisting living cells
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The Debate over Spontaneous Generation
• 1668: Francesco Redi filled jars with decaying meat
Conditions
Results
Jars covered with fine net
No maggots
Open jars
Maggots appeared
Sealed jars
No maggots
From where did the maggots come?
What was the purpose of the sealed jars?
Spontaneous generation or biogenesis?
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The Debate over Spontaneous Generation
• 1745: John Needham put boiled nutrient broth into
covered flasks
Conditions
Results
Nutrient broth heated, then placed Microbial growth
in covered flask
From where did the microbes come?
Spontaneous generation or biogenesis?
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The Debate over Spontaneous Generation
• 1765: Lazzaro Spallanzani boiled nutrient solutions
in sealed flasks
Conditions
Results
Nutrient broth placed in flask,
sealed, then heated
No microbial growth
Spontaneous generation or biogenesis?
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The Theory of Biogenesis
• 1858: Rudolf Virchow said cells arise from
preexisting cells
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The Theory of Biogenesis
• 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,
No microbial growth
heated, then immediately
sealed
Spontaneous generation or biogenesis?
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The Theory of Biogenesis
• Pasteur also used S-shaped flasks
• Keep microbes out but let air in
• Broth in flasks showed no signs of life
• Neck of flask traps microbes
• Microorganisms originate in air or fluids, not
mystical forces
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Figure 1.3 Disproving the Theory of Spontaneous Generation.
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Check Your Understanding
 What evidence supported spontaneous
generation?
1-6
 How was spontaneous generation disproved?
1-7
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A Brief History of Microbiology
Learning Objectives
1-8 Explain how Pasteur's work influenced Lister
and Koch.
1-9 Identify the importance of Koch's postulates.
1-10 Identify the importance of Jenner's work.
1-11 Identify the contributions to microbiology made
by Ehrlich and Fleming.
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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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The Golden Age of Microbiology
• Pasteur showed that microbes are responsible for
fermentation
• Fermentation is the microbial conversion of sugar
to alcohol in the absence of air
• Microbial growth is also responsible for spoilage of
food and beverages
• Bacteria that use air spoil wine by turning it to
vinegar (acetic acid)
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The Golden Age of Microbiology
• Pasteur demonstrated that these spoilage bacteria
could be killed by heat that was not hot enough to
evaporate the alcohol in wine
• Pasteurization is the application of a high heat for
a short time to kill harmful bacteria in beverages
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Figure 1.4 Milestones in the Golden Age of Microbiology (1 of 3).
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The Germ Theory of Disease
• 1835: Agostino Bassi showed that a silkworm
disease was caused by a fungus
• 1865: Pasteur showed that another silkworm
disease was caused by a protozoan
• 1840s: Ignaz Semmelweis advocated
handwashing to prevent transmission of puerperal
fever from one obstetrical patient to another
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The Germ Theory of Disease
• 1860s: Applying Pasteur's work showing that
microbes are in the air, can spoil food, and cause
animal diseases, Joseph Lister used a chemical
antiseptic (phenol) to prevent surgical wound
infections
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Figure 1.4 Milestones in the Golden Age of Microbiology (2 of 3).
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The Germ Theory of Disease
• 1876: Robert Koch discovered that a bacterium
causes anthrax and provided the experimental
steps, Koch's postulates, to demonstrate that a
specific microbe causes a specific disease
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Figure 1.4 Milestones in the Golden Age of Microbiology (3 of 3).
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Vaccination
• 1796: Edward Jenner inoculated a person with
cowpox virus, who was then immune from smallpox
• Vaccination is derived from the Latin word vacca,
meaning cow
• The protection is called immunity
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Check Your Understanding
 Summarize in your own words the germ theory of
disease.
1-8
 What is the importance of Koch's postulates?
1-9
 What is the significance of Jenner's discovery?
1-10
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The Birth of Modern Chemotherapy: Dreams of
a "Magic Bullet"
• Treatment of disease with chemicals is called
chemotherapy
• Chemotherapeutic agents used to treat infectious
disease can be synthetic drugs or antibiotics
• Antibiotics are chemicals produced by bacteria
and fungi that inhibit or kill other microbes
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The First Synthetic Drugs
• Quinine from tree bark was long used to treat
malaria
• 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 were synthesized
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A Fortunate Accident—Antibiotics
• 1928: Alexander Fleming discovered the first
antibiotic (by accident)
• Fleming observed that Penicillium fungus made an
antibiotic, penicillin, that killed S. aureus
• 1940s: Penicillin was tested clinically and massproduced
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Figure 1.5 The discovery of penicillin.
Normal
bacterial
colony
Area of
inhibited
bacterial
growth
Penicillium
colony
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Check Your Understanding
 What was Ehrlich's "magic bullet"?
1-11
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Modern Developments in Microbiology
Learning Objectives
1-12 Define bacteriology, mycology, parasitology,
immunology, and virology.
1-13 Explain the importance of microbial genetics
and molecular biology.
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Bacteriology, Mycology, and Parasitology
• Bacteriology is the study of bacteria
• Mycology is the study of fungi
• Parasitology is the study of protozoa and
parasitic worms
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Figure 1.6 Parasitology: the study of protozoa and parasitic worms.
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Immunology
• Immunology is the study of immunity
• Vaccines and interferons are used to prevent and cure
viral diseases
• A major advance in immunology occurred in 1933
when Rebecca Lancefield classified streptococci
based on their cell wall components
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Figure 1.7 Rebecca Lancefield (1895–1981), who discovered differences in the chemical composition of a
polysaccharide in the cell walls of many pathogenic streptococci.
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Virology
• Virology is the study of viruses
• Dmitri Iwanowski in 1892 and Wendell Stanley in
1935 discovered the cause of mosaic disease of
tobacco as a virus
• Electron microscopes have made it possible to
study the structure of viruses in detail
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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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Recombinant DNA Technology
• 1941: George Beadle and Edward Tatum showed
that genes encode a cell's enzymes
• 1944: Oswald Avery, Colin MacLeod, and Maclyn
McCarty showed that DNA is the hereditary
material
• 1953: James Watson and Francis Crick proposed
a model of DNA structure
• 1961: François Jacob and Jacques Monod
discovered the role of mRNA in protein synthesis
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Figure 1.4 Milestones in the Golden Age of Microbiology.
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Check Your Understanding
 Define bacteriology, mycology, parasitology,
immunology, and virology.
1-12
 Differentiate microbial genetics from molecular
biology.
1-13
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Microbes and Human Welfare
Learning Objectives
1-14 List at least four beneficial activities of
microorganisms.
1-15 Name two examples of biotechnology that use
recombinant DNA technology and two
examples that do not.
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Recycling Vital Elements
• Microbial ecology is the study of the relationship
between microorganisms and their environment
• Bacteria convert carbon, oxygen, nitrogen, sulfur,
and phosphorus into forms used by plants and
animals
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Bioremediation: Using Microbes to Clean Up
Pollutants
• Bacteria degrade organic matter in sewage
• Bacteria degrade or detoxify pollutants such as oil
and mercury
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Figure 27.8 Composting municipal wastes.
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Insect Pest Control by Microorganisms
• Microbes that are pathogenic to insects are
alternatives to chemical pesticides
• Prevent insect damage to agricultural crops and disease
transmission
• Bacillus thuringiensis infections are fatal in many
insects but harmless to animals and plants
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Figure 11.21 Bacillus.
Endospore
Collapsed
B. thuringiensis
Toxic crystal
Bacillus thuringiensis. The diamond-shaped
crystals shown next to the endospore are toxic
to insects that ingest them. This electron
micrograph was made using the technique of
shadow casting.
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Modern Biotechnology and Recombinant DNA
Technology
• Biotechnology is the use of microbes for practical
applications, such as producing foods and
chemicals
• Recombinant DNA technology enables bacteria
and fungi to produce a variety of proteins,
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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Check Your Understanding
 Name two beneficial uses of bacteria.
1-14
 Differentiate biotechnology from recombinant DNA
technology.
1-15
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Microbes and Human Disease
Learning Objectives
1-16 Define normal microbiota and resistance.
1-17 Define biofilm.
1-18 Define emerging infectious disease.
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Normal Microbiota
• Bacteria were once classified as plants, giving rise
to 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 1.8 Several types of bacteria found as part of the normal microbiota on the surface of the human tongue.
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Normal Microbiota
• Normal microbiota prevent growth of pathogens
• Normal microbiota produce growth factors such as
vitamins B and 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
• Biofilms can cause infections and are often
resistant to antibiotics
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Figure 1.9 Biofilm on a catheter.
Staphylococcus
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Emerging Infectious Diseases
• When a pathogen invades a host and overcomes
the host's resistance, disease results
• Emerging infectious diseases (EIDs): new
diseases and diseases increasing in incidence
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Emerging Infectious Diseases
• Middle East respiratory syndrome (MERS)
• Caused by Middle East respiratory syndrome
coronavirus (MERS-CoV)
• Common to SARS
• Severe acute respiratory syndrome
• 100 deaths in the Middle East from 2012 to 2014
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Emerging Infectious Diseases
• Avian influenza A (H5N1)
• Influenza A virus
• Primarily in waterfowl and poultry
• Sustained human-to-human transmission has not yet
occurred
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Figure 13.3b Morphology of an enveloped helical virus.
Spikes
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Emerging Infectious Diseases
• Methicillin-resistant Staphylococcus aureus
(MRSA)
• 1950s: Penicillin resistance developed
• 1980s: Methicillin resistance
• 1990s: MRSA resistance to vancomycin reported
• VISA: vancomycin-intermediate S. aureus
• VRSA: vancomycin-resistant S. aureus
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Emerging Infectious Diseases
• West Nile encephalitis (WNE)
• 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 48 states
• Transmitted between birds and to horses and humans
by mosquitoes
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Diseases in Focus 22.2 (1 of 3)
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Emerging Infectious Diseases
• Bovine spongiform encephalopathy
• Caused by a prion
• An infectious protein that also causes Creutzfeldt-Jakob
disease (CJD)
• New variant of CJD in humans is related to cattle that
have been given feed made from prion-infected sheep
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Figure 22.18b Spongiform encephalopathies.
Holes
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Emerging Infectious Diseases
• E. coli O157:H7
• Toxin-producing strain of E. coli
• First seen in 1982; causes bloody diarrhea
• Leading cause of diarrhea worldwide
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Figure 25.11 Pedestal formation by Enterohemorrhagic E. coli (EHEC) O157:H7.
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Emerging Infectious Diseases
• Ebola hemorrhagic fever (EHF)
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Ebola virus
Causes fever, hemorrhaging, and blood clotting
Transmitted via contact with infected blood or body fluids
First identified near Ebola River, Congo
2014 outbreak in Guinea; hundreds killed
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Figure 23.21 Ebola hemorrhagic virus.
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Emerging Infectious Diseases
• Cryptosporidiosis
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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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Figure 25.17 Cryptosporidiosis.
Intestinal
mucosa
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Oocyst
Emerging Infectious Diseases
• AIDS (acquired immunodeficiency syndrome)
• Caused by human immunodeficiency virus (HIV)
• First identified in 1981
• Sexually transmitted infection affecting males and
females
• Worldwide epidemic infecting 35 million people;
6000 new infections every day
• HIV/AIDS in the United States: 26% are female, and
49% are African American
© 2016 Pearson Education, Inc.
Check Your Understanding
 Differentiate normal microbiota and infectious
disease.
1-16
 Why are biofilms important?
1-17
 What factors contribute to the emergence of an
infectious disease?
1-18
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