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A Brief History of Microbiology Des Moines Area Community College
Chapter 1 A Brief History of Microbiology Azeem Ahmad, Ph.D Des Moines Area Community College (DMACC-URBAN)
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Learning Objectives Invisible world Six classes of microorganisms Prokaryotes, Archaea and Eukaryotes Viruses Spontaneous generation Koch postulates Gram stain Infection and disease Genetics Modern microbiology
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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 © 2012 Pearson Education Inc. 3
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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
Protozoa and bacteria-microbial world was looked at and started to describe
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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 © 2012 Pearson Education Inc. 6
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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 © 2012 Pearson Education Inc. 7
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Figure 1.4 Cells of the bacterium Streptococcus
Prokaryotic bacterial cells Nucleus of eukaryotic cheek cell
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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 © 2012 Pearson Education Inc. 9
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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 © 2012 Pearson Education Inc. 11
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Figure 1.6 Locomotive structures of protozoa-overview
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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 © 2012 Pearson Education Inc. 13
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Figure 1.7 Algae-overview
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Figure 1.9 Viruses infecting a 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? © 2012 Pearson Education Inc. 16
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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 © 2012 Pearson Education Inc. 17
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The Golden Age of Microbiology
Pasteur’s Experiments When the “swan-necked” flasks remained upright, no microbial growth appeared When the flask was tilted, dust from the bend in the neck seeped back into the flask and made the infusion cloudy with microbes within a day © 2012 Pearson Education Inc. 18
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Figure Louis Pasteur
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Figure 1.12 Pasteur’s experiments with “swan-necked” flasks
Steam escapes from open end of flask. Dust from air settles in bend. Air moves in and out of flask. Months Infusion is heated. Infusion sits; no microbes appear. Infusion remains sterile indefinitely.
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The Golden Age of Microbiology
The Scientific Method Spontaneous generation debate led in part to scientific method Observation leads to question Question generates hypothesis Hypothesis is tested through experiment(s) Results prove or disprove hypothesis Accepted hypothesis leads to theory/law Reject or modify hypothesis © 2012 Pearson Education Inc. 21
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Figure 1.13 The scientific method
Observations Question Repeat Experimental data support hypothesis Accept hypothesis Theory or law Experiment, including control groups Hypothesis Observations Reject hypothesis Experimental data do not support hypothesis Modify hypothesis Modified hypothesis
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Figure 1.14 Pasteur's application of the scientific method
Observation: Fermenting grape juice Microscopic analysis shows juice contains yeasts and bacteria. Hypothesis Experiment Observation Conclusion Day 1: Flasks of grape juice are heated sufficiently to kill all microbes. Day 2 I. Spontaneous fermentation occurs. No fermentation; juice remains free of microbes Reject hypothesis I. Flask is sealed. II. Air ferments grape juice. No fermentation; juice remains free of microbes Reject hypothesis II. Flask remains open to air via curved neck. III. Bacteria ferment grape juice into alcohol. Bacteria reproduce; acids are produced. Modify hypothesis III; bacteria ferment grape juice into acids. Juice in flask is inoculated with bacteria and sealed. IV. Yeasts ferment grape juice into alcohol. Yeasts reproduce; alcohol is produced. Accept hypothesis IV; yeasts ferment grape juice into alcohol. Juice in flask is inoculated with yeast and sealed.
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Table 1.1 Some Industrial Uses of Microbes
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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 © 2012 Pearson Education Inc. 25
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Figure Robert Koch
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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 © 2012 Pearson Education Inc. 27
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Figure 1.16 Bacterial colonies on agar
Bacterium 6 Bacterium 7 Bacterium 5 Bacterium 8 Bacterium 4 Bacterium 9 Bacterium 3 Bacterium 10 Bacterium 2 Bacterium 11 Bacterium 1 Bacterium 12
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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 © 2012 Pearson Education Inc. 29
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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 © 2012 Pearson Education Inc. 30
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Figure 1.17 Results of Gram staining
Gram-positive Gram-negative
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Figure 1.19 Some scientific disciplines and applications
BIOLOGISTS MODERN DISCIPLINES Bacteriology (bacteria) Protozoology (protozoa) Mycology (fungi) Parasitology (protozoa and animals) Phycology (algae) Pre-1857 Leeuwenhoek Linnaeus Taxonomy Semmelweiss Snow Infection control Epidemiology The Golden Age of Microbiology (1857–1907) Industrial microbiology Pasteur Pasteurization Food and beverage technology Microbial metabolism Genetics Genetic engineering Buchner Koch Koch’s postulates Etiology Ivanowski Virology Beijerinck Winogradsky Environmental microbiology Ecological microbiology Gram Microbial morphology Lister Nightingale Antiseptic medical techniques Hospital microbiology Jenner von Behring Kitasato Serology Immunology Ehrlich Chemotherapy Fleming Pharmaceutical microbiology
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Table 1.3 Fields of Microbiology
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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 © 2012 Pearson Education Inc. 34
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The Modern Age of Microbiology
How Do Genes Work? Microbial genetics Molecular biology Recombinant DNA technology Gene therapy © 2012 Pearson Education Inc. 35
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The Modern Age of Microbiology
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 © 2012 Pearson Education Inc. 36
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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 Cat scratch disease caused by unculturable organism © 2012 Pearson Education Inc. 37
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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 © 2012 Pearson Education Inc. 38
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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 © 2012 Pearson Education Inc. 39
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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 © 2012 Pearson Education Inc. 40
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Fungus colony (Penicillium)
Figure Effects of penicillin on a bacterial “lawn” in a petri dish Fungus colony (Penicillium) Zone of inhibition Bacterial colonies (Staphylococcus)
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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 © 2012 Pearson Education Inc. 42
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