6/1/2011MDufilho1 Chapter 1 A Brief History of Microbiology

6/1/2011MDufilho2 Introduction What Does Life Really Look Like? What is Microbiology? What kinds of questions do Microbiologists ask?

6/1/2011MDufilho3 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

6/1/2011MDufilho4 Figure 1.1 Antoni van Leeuwenhoek

6/1/2011MDufilho5 Figure 1.2 Reproduction of Leeuwenhoek’s microscope Specimen holder Lens

6/1/2011MDufilho6 Figure 1.3 The microbial world

Leeuwenhoek Crypt - Delft 7

6/1/2011MDufilho8 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

6/1/2011MDufilho9 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

6/1/2011MDufilho10 Figure 1.4 Cells of the bacterium Streptococcus Nucleus of eukaryotic cheek cell Prokaryotic bacterial cells

6/1/2011MDufilho11 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.

6/1/2011MDufilho12 Figure 1.5 Fungi-overview

6/1/2011MDufilho13 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.

6/1/2011MDufilho14 Figure 1.6 Locomotive structures of protozoa-overview

6/1/2011MDufilho15 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.

6/1/2011MDufilho16 Figure 1.7 Algae-overview

6/1/2011MDufilho17 Figure 1.8 An immature stage of a parasitic worm in blood Red blood cell

6/1/2011MDufilho18 Figure 1.9 Viruses infecting a bacterium Virus Bacterium Viruses assembling inside cell

6/1/2011MDufilho19 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?

6/1/2011MDufilho20 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

6/1/2011MDufilho21 Figure 1.10 Redi’s experiments Flask unsealed Flask sealed Flask covered with gauze

6/1/2011MDufilho22 Figure 1.11 Louis Pasteur

6/1/2011MDufilho23 Figure 1.12 Pasteur’s experiments with “swan-necked” flasks Steam escapes from open end of flask. Infusion is heated. Infusion sits; no microbes appear. Months Air moves in and out of flask. Infusion remains sterile indefinitely. Dust from air settles in bend.

Pasteur Institute – Paris 24

6/1/2011MDufilho25 Figure 1.14 Pasteur's application of the scientific method Observation: Hypothesis Experiment Observation Conclusion Fermenting grape juice Microscopic analysis shows juice contains yeasts and bacteria. Day 1: Flasks of grape juice are heated sufficiently to kill all microbes. Day 2 I. Spontaneous fermentation occurs. II. Air ferments grape juice. III. Bacteria ferment grape juice into alcohol. IV. Yeasts ferment grape juice into alcohol. Juice in flask is inoculated with yeast and sealed. Juice in flask is inoculated with bacteria and sealed. Flask remains open to air via curved neck. Flask is sealed. No fermentation; juice remains free of microbes Bacteria reproduce; acids are produced. Yeasts reproduce; alcohol is produced. Reject hypothesis I. Reject hypothesis II. Modify hypothesis III ; bacteria ferment grape juice into acids. Accept hypothesis IV ; yeasts ferment grape juice into alcohol.

6/1/2011MDufilho26 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.

6/1/2011MDufilho27 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.

6/1/2011MDufilho28 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.

6/1/2011MDufilho29 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.

6/1/2011MDufilho30 Figure 1.17 Results of Gram staining Gram-positive Gram-negative

6/1/2011MDufilho31 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 © 2012 Pearson Education Inc.

6/1/2011MDufilho32 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.

6/1/2011MDufilho33 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 © 2012 Pearson Education Inc.

6/1/2011MDufilho34 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 © 2012 Pearson Education Inc.

6/1/2011MDufilho35 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.

6/1/2011MDufilho36 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.

6/1/2011MDufilho37 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.

6/1/2011MDufilho38 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.