Chapter 1 A Brief History of Microbiology
What is a microbe/ microorganism? A microbe is a living organism that require a microscope to be seen - Microbial cells range in size from millimeters (mm) to 0.2 micrometer (µm) - Viruses may be ten times smaller Some microbes consist of a single cell Each microbe contains in its genome the capacity to reproduce its own kind
Microbiology Microbiology: The study of organisms too small to be seen without magnification To figure what a microbe is, we have to use tools such as microscopes
The Early Years of Microbiology What Does Life Really Look Like? Antoni van Leeuwenhoek 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
Antoni van Leeuwenhoek Figure 1.1
Reproduction of Leeuwenhoek's microscope Lens Specimen holder Figure 1.2
Microscopes reveal the microbial world Robert Hooke (1635 1703) Built the first compound microscope Used it to observe mold Published Micrographia, the first manuscript that illustrated objects under the microscope Coined the term cell http://archive.nlm.nih.gov/proj/ttp/flash/hooke/hooke.html
Figure 1.3 The microbial world
The Early Years of Microbiology How Can Microbes Be Classified? Carolus Linnaeus developed taxonomic system for naming plants and animals and grouping similar organisms together Leeuwenhoek's microorganisms now grouped into six categories as follows: Bacteria Archaea Fungi Protozoa Algae Small multicellular animals
Microbial structure Two cell types Prokaryote microscopic, unicellular organisms, lack nuclei and membrane-bound organelles Eukaryote unicellular (microscopic) and multicellular, have nucleus and membrane-bound organelles Viruses - Acellular, parasitic particles composed of a nucleic acid and protein
Broad classification of Bacteria & Archaea Prokaryotes Unicellular, lack nuclei, much smaller than eukaryotes Found everywhere there is sufficient moisture (ubiquitous) Some isolated from extreme environments Reproduce asexually Bacterial cell walls contain peptidoglycan; some lack cell walls Archaeal cell walls composed of polymers other than peptidoglycan
Cells of the bacterium Streptococcus (dark blue) and two human cheek cells Prokaryotic bacterial cells Nucleus of eukaryotic cheek cell Figure 1.4
Broad classification of fungi Eukaryotic (have membrane-bound nucleus) Obtain food from other organisms Possess cell walls Fungi Molds multicellular; grow as long filaments; reproduce by sexual and asexual spores Yeasts unicellular reproduce asexually by budding some produce sexual spores
Hyphae Spores Fungi Budding cells Figure 1.5
Broad classification of 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: 1) Pseudopods cell extensions that flow in direction of travel 2) Cilia numerous short protrusions that propel organisms through environment 3) Flagella extensions of a cell that are fewer, longer, and more whiplike than cilia
Locomotive structures of protozoa Nucleus Pseudopods Cilia Flagellum Figure 1.6
Broad classification of Algae Unicellular or multicellular Photosynthetic Simple reproductive structures Categorized on the basis of pigmentation and composition of cell wall Figure 1.7
Other organisms that microbiologists study Parasites: live on or in the body of another organism called the host and it damages the host Viruses: Acellular, parasitic particles composed of a nucleic acid and protein
An immature stage of a parasitic worm in blood Red blood cell Parasitic worm Figure 1.8
A colorized electron microscope image of viruses infecting a bacterium Virus Bacterium Viruses assembling inside cell Figure 1.9
Four questions: the search for answers 1) Is spontaneous generation of microbial life possible? 2) What causes fermentation? 3) What causes disease? 4) How can we prevent infection and disease? The Golden Age of Microbiology
Spontaneous generation: are parents necessary? Spontaneous generation (Abiogenesis) is an early belief that some forms of life could arise from vital forces present in nonliving or decomposing matter (flies from manure, maggots from decaying meat, etc.) Francesco Redi (1660s) = showed that maggots in decaying meat were the offspring of flies Lazzaro Spallanzani (1760s) = showed that a sealed flask of meat broth sterilized by boiling failed to grow microbes Louis Pasteur (1860s) eventually disproved spontaneous generation and proved the Theory of Biogenesis
Can microbial life spontaneously generate- Abiogenesis? Some philosophers and scientists of the past thought living things arose from three processes: 1) Asexual reproduction 2) Sexual reproduction 3) Nonliving matter Aristotle proposed spontaneous generation: Living things can arise from nonliving matter
Francesco Redi s experiments When decaying meat was kept isolated from flies, maggots never developed Meat exposed to flies was soon infested As a result, scientists began to doubt Aristotle's theory Figure 1.10
John Needham s experiments Scientists did not believe animals could arise spontaneously, but believed microbes could. Everyone knew that boiling killed microorganisms, so Needham proposed to test whether or not microorganisms appeared spontaneously after boiling. He boiled beef broth, put it into a flask, sealed it, and waited - sure enough, microorganisms grew. Needham's experiments (1745) with beef gravy and infusions of plant material reinforced the idea of spontaneous generation.
Lazzaro Spallanzani s experiments Thought Needham failed to heat vials sufficiently to kill all microbes or had not sealed vials tightly enough. Microorganisms exist in air and can contaminate experiments. To test his theory, he modified Needham's experiment - he placed the chicken broth in a flask, sealed the flask, drew off the air to create a partial vacuum, then boiled the broth. No microorganisms grew. Proponents of spontaneous generation argued that Spallanzani had only proven that spontaneous generation could not occur without air.
Louis Pasteur Figure 1.11
Pasteur s experiments with swan-necked flasks Figure 1.12 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
Theory of biogenesis: Yes! Parents are necessary!! The idea that living things can only arise from other living things
The scientific method Debate over spontaneous generation led in part to development of scientific method Figure 1.13
Deductive reasoning Theory Hypothesis Observation Scientific Method Inductive reasoning Observation Pattern Tentative hypothesis Confirmation Theory If evidence of a theory is so compelling that the next level of confidence is reached, it becomes a Law or principle If hypothesis is supported by a growing body of evidence and survives rigorous scrutiny, it moves to the next level of confidence - it becomes a theory
Four questions: the search for answers 1) Is spontaneous generation of microbial life possible? 2) What causes fermentation? 3) What causes disease? 4) How can we prevent infection and disease?
What Causes Fermentation? Spoiled wine threatened livelihood of vintners. Some believed air caused fermentation; others insisted living organisms caused fermentation. Vintners funded research of methods to promote production of alcohol and prevent spoilage during fermentation. This debate also linked to debate over spontaneous generation.
Pasteur applied the scientific method to investigate fermentation Figure 1.14
Pasteur's contributions Led to the development of pasteurization: Process of heating liquids just enough to kill most bacteria Began the field of industrial microbiology Intentional use of microbes for manufacturing products
Fermentation and Biochemistry (Buchner s experiments) Demonstrated fermentation does not require living cells Showed enzymes promote chemical reactions resulting in fermentation Began the field of biochemistry http://www.nobelprize.org
Four questions: the search for answers 1) Is spontaneous generation of microbial life possible? 2) What causes fermentation? 3) What causes disease? 4) How can we prevent infection and disease?
Microbial disease devastates human populations Throughout history, microbial diseases have profoundly affected human demographics and cultural practices. Fourteenth century = bubonic plague caused by Yersinia pestis Nineteenth century = tuberculosis caused by Mycobacterium tuberculosis Today = acquired immunodeficiency syndrome (AIDS) caused by the human immunodeficiency virus (HIV)
Microbial disease devastates human populations A.) Medieval church procession to ward off the Black Death (bubonic plague). B.) The AIDS memorial quilt spread before the Washington Monument. Each panel of the quilt memorializes an individual who died of AIDS. C.) Ebola virus 2014 outbreak Nature, Oct 2014. Centre for Infections/Public Health England/SPL
What causes disease? Pasteur developed germ theory of disease Robert Koch studied causative agents of disease (etiology) Anthrax Examined colonies of microorganisms
Figure 1.15 Robert Koch
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
Bacterial colonies on a solid surface (agar) Bacterium 2 Bacterium 1 Bacterium 3 Bacterium 4 Bacterium 6 Bacterium 7 Bacterium 5 Bacterium 8 Bacterium 9 Bacterium 10 Bacterium 11 Bacterium 12 Figure 1.16
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 Introduction of agent into healthy, susceptible host should result in same disease Same agent must be found in the diseased experimental host
Gram stain: A differential staining procedure The Gram stain was devised in 1884 by the Dutch physician Hans Christian Gram (1853 1938) It differentiates between two types of bacteria: Gram-positive bacteria retain the crystal violet stain because of their thicker cell wall Gram-negative bacteria do not retain the crystal violet stain because of their thinner cell wall
Results of Gram staining Gram-positive Gram-negative Figure 1.17
Four questions: the search for answers 1) Is spontaneous generation of microbial life possible? 2) What causes fermentation? 3) What causes disease? 4) How can we prevent infection and disease?
How Can We Prevent Infection and Disease? Semmelweis and handwashing Lister's antiseptic technique Nightingale Medical statistics and nursing Snow infection control and epidemiology Jenner's vaccine field of immunology Ehrlich's "magic bullets" field of chemotherapy
Florence Nightingale Figure 1.18
Scientific disciplines and applications arising from the pioneering work of scientists Figure 1.19
Microbiology and the Basic Chemical Reactions of Life Biochemistry - Began with Pasteur's work on fermentation and Buchner's discovery of enzymes in yeast extract Kluyver and van Niel microbes used as model systems for biochemical reactions Practical applications Design of herbicides and pesticides Diagnosis of illnesses and monitoring of patients' responses to treatment Treatment of metabolic diseases Drug design
How Do Genes Work? Microbial genetics Molecular biology Recombinant DNA technology Gene therapy
Microbial genetics Avery, MacLeod, and McCarty determined genes are part of DNA Beadle and Tatum established that 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
How Do Genes Work? Molecular Biology: Explanation of cell function at the molecular level Pauling proposed that gene sequences could provide understanding of evolutionary relationships and processes Identify existence of microbes that have never been cultured Woese determined cells belong to bacteria, archaea, or eukaryotes Cat scratch disease caused by unculturable organism
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
What Role 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 The flow of energy and food through the earth s ecosystems Photosynthesis: Light fueled conversion of carbon dioxide to organic material Decomposition: Breakdown of dead matter and wastes into simple compounds
How Do We Defend Against Disease? Serology : The study of blood serum Von Behring and Kitasato existence of chemicals and cells that fight infection in the blood Immunology : The study of the body's defenses against specific pathogens Chemotherapy : Fleming discovered penicillin Domagk discovered sulfa drugs
The effects of penicillin on a bacterial "lawn" in a Petri dish. Fungus colony (Penicillium) Zone of inhibition Bacteria (Staphylococcus) Figure 1.20