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Chapter 1 A Brief History of Microbiology 6/1/2011 MDufilho 1 Introduction • What Does Life Really Look Like? • What is Microbiology? • What kinds of questions do Microbiologists ask? 6/1/2011 MDufilho 2 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 6/1/2011 MDufilho 3 Figure 1.1 Antoni van Leeuwenhoek 6/1/2011 MDufilho 4 Figure 1.2 Reproduction of Leeuwenhoek’s microscope Lens Specimen holder 6/1/2011 MDufilho 5 Figure 1.3 The microbial world 6/1/2011 MDufilho 6 Leeuwenhoek Crypt - Delft 7 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 6/1/2011 MDufilho 8 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 6/1/2011 MDufilho 9 Figure 1.4 Cells of the bacterium Streptococcus Nucleus of Prokaryotic bacterial cells eukaryotic cheek cell 6/1/2011 MDufilho 10 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 11 Figure 1.5 Fungi-overview 6/1/2011 MDufilho 12 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 13 Figure 1.6 Locomotive structures of protozoa-overview 6/1/2011 MDufilho 14 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 15 Figure 1.7 Algae-overview 6/1/2011 MDufilho 16 Figure 1.8 An immature stage of a parasitic worm in blood Red blood cell 6/1/2011 MDufilho 17 Figure 1.9 Viruses infecting a bacterium Virus Bacterium Viruses assembling inside cell 6/1/2011 MDufilho 18 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? 6/1/2011 MDufilho 19 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 6/1/2011 MDufilho 20 Figure 1.10 Redi’s experiments Flask unsealed 6/1/2011 Flask sealed MDufilho Flask covered with gauze 21 Figure 1.11 Louis Pasteur 6/1/2011 MDufilho 22 Figure 1.12 Pasteur’s experiments with “swan-necked” flasks Steam escapes from open end of flask. Infusion is heated. 6/1/2011 Air moves in and out of flask. Infusion sits; no microbes appear. MDufilho Months Dust from air settles in bend. Infusion remains sterile indefinitely. 23 Pasteur Institute – Paris 24 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. 6/1/2011 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 25 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 26 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 27 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 28 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 29 Figure 1.17 Results of Gram staining Gram-positive Gram-negative 6/1/2011 MDufilho 30 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 31 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 32 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 33 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 34 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 35 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 36 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 37 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 6/1/2011 © 2012 Pearson Education Inc. MDufilho 38