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Chapter 1: Scope and History of Microbiology
Microorganisms and Microbiology
• Microbiology is the study of microorganisms
• Microscopic, single cell, cluster, chains
carry out life processes independently as single cells
• Viruses- microscopic, non-cellular, RNA or DNA
• Bacteria and their processes and their effects on society, humans, animals and
environment
Two basic themes:
1. Basic- cellular processes
2. Applied – practical problems in agriculture, health and industry
Importance of microorganisms
1. evolution of oxygen and first cells on early Earth
2. activities affect the entire web of life on Earth
Microorganisms and Their Environment
Microbes exist in populations that occupy a location in the environment (habitat)
• Populations of cells rarely live alone and form assemblages of different populations (microbial
communities)
• Microbial communities: free swimming or biofilms (attached to a surface)
• Interactions between communities may be:
1. beneficial – cooperative feeding efforts (waste-nutrient)
2. harmful - waste product is inhibitory
•
Ecosystem: Living organisms together with physical and chemical constituents of environment
Extent of Microbial Life
• Strength is in numbers: 5 x 1030 for prokaryotes (bacteria)
•
Total carbon in this number of small cells equals that of all plants on Earth
• Prokaryotic cells
1. constitute the major portion of biomass on Earth
2. Key reservoirs of essential nutrients for life
•
Most of the prokaryotes are in oceanic and terrestrial subsurfaces
Microbes and Agriculture
• Nitrogen fixation
1. association between plants (legumes) and bacteria
2. reduce need for fertilizer
•
Rumen microbes in cattle and sheep allow them to breakdown/digest grass and hay
•
Nutrient cycling (C, N, and S)
•
Plant and animal diseases
1. Microorganisms and Food
– prevent microbial spoilage of food and food borne disease
– Manufacturing of foods
2. Microorganisms, energy and environment
– Natural gas (methane)
– Ethanol (biofuel)
– Bioremediation
3. Microbes and the future
– Biotechnology-genetic engineering
Microorganisms are especially useful in research…
1. Have relatively simple structures
2. Large numbers of microbes can be used in an experiment to obtain statistically reliable results at a
reasonable cost
3. Reproduce quickly so they are useful for studies involving transfer of genetic information
Microorganisms
1. Bacteria
2. Fungi
3. Protozoa
4. Algae
5. Viruses
Bacteria (singular: bacterium)
•Single-celled organisms
•Prokaryotes
•Shapes:
1. Spherical
2. Rod
3. Spiral
Algae (singular: alga)
•Single-celled microorganisms
•Eukaryotic
•Nucleus and membrane-bound organelles
•Photosynthetic
•Fresh water and marine environments
Fungi (singular: fungus)
•Single-celled microorganisms (Yeasts)
•Multi-cellular microorganisms (Molds)
•Eukaryotic
•Widely distributed in water and soil as decomposers of dead organisms
•Some are important in medicine
Protozoa (singular: protozoan)
•Single-celled, microorganisms
•Eukaryotic
•Have a nucleus (membrane-bound) and other intracellular structures
•Found in a variety of water and soil environments
Viruses
•Acellular entities too small to be seen with a light microscope
•Composed of nucleic acid and protein
•Bacteriophage: viruses that infect bacteria
•Viroids: nucleic acid without a protein coating
•Prions: Infectious proteinaeceous particles
Historical Roots of Microbiology
-1664: Robert Hooke
-1684 – A. V. Leeuwenhoek
-Ferdinand Cohn: founder of bacteriology
- Louis Pasteur: Disproved Spontaneous generation, vaccination, pasteurization
-Robert Koch: germ theory, demonstrates that specific microorganisms cause specific disease
(Koch’s postulates)
Isolation of harmful pathogens
developed techniques that furthered advancement of Microbiology
Theories of Microbiology
•The Cell Theory: All cells are the fundamental units of life and carry out all basic functions of living
things
•The Germ Theory of Disease:
States that microorganisms can invade other organisms and cause
disease
Disproof of Spontaneous Generation
•Francesco Redi
•Lazzaro Spallanzani
•Louis Pasteur
•John Tyndall
Historical Scientists in Microbiology
1. Antony van Leeuwenhoek
2. Louis Pasteur
3. Joseph Lister
4. Edward Jenner
5. Elie Metchnikoff
6. Paul Ehrlich
7. Alexander Fleming
Pasteur’s Further Contributions
•Developed the technique of pasteurization to kill unwanted microorganisms
•Association of specific organisms with particular diseases
•Development of vaccines
Koch’s Postulates
•The microbe must be present in every case of the disease but absent from healthy organisms
•The suspected microbe must be isolated and grown in a pure culture
•The same disease must result when the isolated microbe is inoculated into a healthy host
•The same microbe must be isolated again from the diseased host
Techniques for Studying Microorganisms
•Fannie Hesse suggested that agar could be used as a solidifying agent
•Richard Petri developed the petri dish which was used to contain the solid culture media (agar and
nutrients)
•Robert Koch used these techniques to isolate the bacterium that caused tuberculosis
Work Toward Controlling Infections
•Ignaz Phillip Semmelweis
•Joseph Lister
Emergence of Special Fields of Microbiology
•Immunology
•Virology
•Chemotherapy
•Genetics and Molecular Biology