Transcript Document

Chapter 1
A Brief
History of
Microbiology
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Introduction
• What Does Life Really Look Like?
• What is Microbiology?
• What kinds of questions do Microbiologists ask?
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The Early Years of Microbiology
• What Does Life Really Look Like?
– Antoni van Leeuwenhoek (Dutch)
– Began making and using simple microscopes
– Often made a new microscope for each specimen
– Examined water and visualized tiny animals, fungi,
algae, and single-celled protozoa: “animalcules”
– By end of 19th century, these organisms were called
microorganisms
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Figure 1.1 Antoni van Leeuwenhoek
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Figure 1.2 Reproduction of Leeuwenhoek’s microscope
Lens Specimen holder
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Figure 1.3 The microbial world
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Leeuwenhoek Crypt - Delft
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The Early Years of Microbiology
• How Can Microbes Be Classified?
– Carolus Linnaeus developed taxonomic system
for grouping similar organisms together
– Leeuwenhoek’s microorganisms grouped into six
categories:
– Bacteria
– Archaea
– Fungi
– Protozoa
– Algae
– Small multicellular animals
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The Early Years of Microbiology
• Bacteria and Archaea
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–
–
–
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Unicellular and lack nuclei
Much smaller than eukaryotes
Found everywhere there is sufficient moisture
Reproduce asexually
Two kinds
– Bacteria – cell walls contain peptidoglycan
– Archaea – cell walls composed of polymers
other than peptidoglycan
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Figure 1.4 Cells of the bacterium Streptococcus
Nucleus of
Prokaryotic
bacterial cells eukaryotic cheek cell
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The Early Years of Microbiology
• Fungi
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–
–
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Eukaryotic (have membrane-bound nucleus)
Obtain food from other organisms
Possess cell walls
Include
– Molds – multicellular; grow as long filaments;
reproduce by sexual and asexual spores
– Yeasts – unicellular; reproduce by budding or
sexual spores
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Figure 1.5 Fungi-overview
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The Early Years of Microbiology
• Protozoa
– Single-celled eukaryotes
– Similar to animals in nutrient needs and cellular
structure
– Live freely in water; some live in animal hosts
– Asexual (most) and sexual reproduction
– Most are capable of locomotion by
– Pseudopodia
– Cilia
– Flagella
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Figure 1.6 Locomotive structures of protozoa-overview
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The Early Years of Microbiology
• Algae
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–
–
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Unicellular or multicellular
Photosynthetic
Simple reproductive structures
Categorized on the basis of pigmentation,
storage products, and composition of cell wall
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Figure 1.7 Algae-overview
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Figure 1.8 An immature stage of a parasitic worm in blood
Red blood cell
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Figure 1.9 Viruses infecting a bacterium
Virus
Bacterium
Viruses
assembling
inside cell
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The Golden Age of Microbiology
• Scientists searched for answers to four
questions
– Is spontaneous generation of microbial life
possible?
– What causes fermentation?
– What causes disease?
– How can we prevent infection and disease?
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The Golden Age of Microbiology
• Some thought living things arose from
three processes
– Asexual reproduction
– Sexual reproduction
– Nonliving matter
• Aristotle proposed spontaneous
generation
– Living things can arise from nonliving matter
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Figure 1.10 Redi’s experiments
Flask unsealed
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Flask sealed
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Flask covered
with gauze
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Figure 1.11 Louis Pasteur
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Figure 1.12 Pasteur’s experiments with “swan-necked” flasks
Steam escapes
from open end
of flask.
Infusion
is heated.
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Air moves in
and out of flask.
Infusion sits;
no microbes appear.
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Months
Dust from
air settles
in bend.
Infusion remains
sterile indefinitely.
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Pasteur Institute – Paris
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Figure 1.14 Pasteur's application of the scientific method
Observation:
Microscopic analysis
shows juice contains
yeasts and bacteria.
Fermenting
grape juice
Hypothesis
Experiment
Observation
Conclusion
Day 1: Flasks of grape
Day 2
juice are heated sufficiently
to kill all microbes.
I. Spontaneous
fermentation
occurs.
II. Air ferments
grape juice.
III. Bacteria ferment
grape juice
into alcohol.
IV. Yeasts ferment
grape juice
into alcohol.
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Flask is
sealed.
Flask remains
open to air
via curved neck.
Juice in flask is
inoculated with
bacteria and sealed.
Juice in flask is
inoculated with MDufilho
yeast and sealed.
No fermentation;
juice remains
free of microbes
Reject
hypothesis I.
No fermentation;
juice remains
free of microbes
Reject
hypothesis II.
Bacteria reproduce;
acids are produced.
Modify hypothesis
III; bacteria ferment
grape juice into
acids.
Yeasts reproduce;
alcohol is produced.
Accept hypothesis
IV; yeasts ferment
grape juice into
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alcohol.
The Golden Age of Microbiology
• What Causes Disease?
– Pasteur developed germ theory of disease
– Robert Koch studied causative agents of
disease
– Anthrax
– Examined colonies
of microorganisms
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The Golden Age of Microbiology
• Koch’s Contributions
– Simple staining techniques
– First photomicrograph of bacteria
– First photomicrograph of bacteria in diseased
tissue
– Techniques for estimating CFU/ml
– Use of steam to sterilize media
– Use of Petri dishes
– Techniques to transfer bacteria
– Bacteria as distinct species
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The Golden Age of Microbiology
• Koch’s Postulates
– Suspected causative agent must be found in
every case of the disease and be absent from
healthy hosts
– Agent must be isolated and grown outside
the host
– When agent is introduced into a healthy,
susceptible host, the host must get the disease
– Same agent must be found in the diseased
experimental host
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The Golden Age of Microbiology
• Gram’s Stain
– Danish scientist Hans Christian Gram developed
more important staining technique than Koch’s
in 1884
– Involves the applications of a series of dyes
– Some microbes are left purple, now labeled
Gram-positive
– Other microbes are left pink, now labeled Gramnegative
– Gram procedure used to separate into two
groups
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Figure 1.17 Results of Gram staining
Gram-positive Gram-negative
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The Golden Age of Microbiology
• How Can We Prevent Infection and
Disease?
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Semmelweis and handwashing
Lister’s antiseptic technique
Nightingale and nursing
Snow – infection control and epidemiology
Jenner’s vaccine – field of immunology
Ehrlich’s “magic bullets” – field of
chemotherapy
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The Modern Age of Microbiology
• What Are the Basic Chemical Reactions of Life?
– Biochemistry
– Began with Pasteur’s and Buchner’s works
– Microbes used as model systems for biochemical
reactions
– Practical applications
– Design of herbicides and pesticides
– Diagnosis of illness and monitoring responses to
treatment
– Treatment of metabolic diseases
– Drug design
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The Modern Age of Microbiology
How do Genes Work?
• Microbial Genetics
– Avery, MacLeod, and McCarty: genes are
contained in molecules of DNA
– Beadle and Tatum: a gene’s activity is related to
protein function
– Translation of genetic information into protein
explained
– Rates and mechanisms of genetic mutation
investigated
– Control of genetic expression by cells described
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The Modern Age of Microbiology
• Molecular Biology
– Explanation of cell function at the molecular level
– Pauling proposed that gene sequences could
– Provide understanding of evolutionary
relationships/processes
– Establish taxonomic categories
– Identify microbes that have never been cultured
– Woese determined cells belong to bacteria,
archaea, or eukaryotes
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The Modern Age of Microbiology
• Recombinant DNA Technology
– Genes in microbes, plants, and animals
manipulated for practical applications
– Production of human blood-clotting factor by
E. coli to aid hemophiliacs
• Gene Therapy
– Inserting a missing gene or repairing a defective
one in humans by inserting desired gene into
host cells
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The Modern Age of Microbiology
• What Roles Do Microorganisms Play in the
Environment?
– Bioremediation uses living bacteria, fungi,
and algae to detoxify polluted environments
– Recycling of chemicals such as carbon,
nitrogen, and sulfur
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The Modern Age of Microbiology
• How Do We Defend Against Disease?
– Serology
– The study of blood serum
– Blood contains chemicals and cells that fight
infection
– Immunology
– The study of the body’s defense against specific
pathogens
– Chemotherapy
– Fleming discovered penicillin
– Domagk discovered sulfa drugs
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The Modern Age of Microbiology
• What Will the Future Hold?
– Microbiology is built on asking and answering
questions
– The more questions we answer, the more
questions we have
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