6/1/2011mdufilho1 chapter 1 a brief history of microbiology
TRANSCRIPT
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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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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– 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 ofeukaryotic cheek cell
Prokaryoticbacterial cells
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The Early Years of Microbiology
• Fungi– 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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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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The Early Years of Microbiology
• Algae– 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 1.9 Viruses infecting a bacterium
Virus
Bacterium
Virusesassemblinginside 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 Flask sealed Flask coveredwith gauze
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Figure 1.12 Pasteur’s experiments with “swan-necked” flasks
Steam escapesfrom open endof flask.
Infusionis heated.
Infusion sits;no microbes appear.
Months
Air moves inand out of flask.
Infusion remainssterile indefinitely.
Dust fromair settlesin bend.
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Figure 1.14 Pasteur's application of the scientific method
Observation:
Hypothesis Experiment Observation Conclusion
Fermentinggrape juice
Microscopic analysisshows juice containsyeasts and bacteria.
Day 1: Flasks of grapejuice are heated sufficientlyto kill all microbes.
Day 2
I. Spontaneousfermentationoccurs.
II. Air fermentsgrape juice.
III. Bacteria fermentgrape juiceinto alcohol.
IV. Yeasts fermentgrape juiceinto alcohol.
Juice in flask is inoculated withyeast and sealed.
Juice in flask is inoculated withbacteria and sealed.
Flask remainsopen to airvia curved neck.
Flask is sealed.
No fermentation;juice remainsfree of microbes
No fermentation;juice remainsfree of microbes
Bacteria reproduce;acids are produced.
Yeasts reproduce;alcohol is produced.
Reject hypothesis I.
Reject hypothesis II.
Modify hypothesis III; bacteria fermentgrape juice intoacids.
Accept hypothesis IV; yeasts fermentgrape juice intoalcohol.
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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 Gram-
negative– Gram procedure used to separate into two
groups
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The Golden Age of Microbiology
• How Can We Prevent Infection and Disease?
– 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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