Chapter Summary
Microbes in Our Lives (p. 2)
1. Living things too small to be seen with the unaided eye are called microorganisms.
2. Microorganisms are important in maintaining Earth’s ecological balance.
3. Some microorganisms live in humans and other animals and are needed to maintain good health.
4. Some microorganisms are used to produce foods and chemicals.
5. Some microorganisms cause disease.
Naming and Classifying Microorganisms (pp. 2–6)
Nomenclature (p. 2)
1. In a nomenclature system designed by Carolus Linnaeus (1735), each living organism is assigned two names.
2. The two names consist of a genus and a specific epithet, both of which are underlined or italicized.
Types of Microorganisms (pp. 3–6)
Bacteria (pp. 3–4)
3. Bacteria are unicellular organisms. Because they have no nucleus, the cells are described as prokaryotic.
4. The three major basic shapes of bacteria are bacillus, coccus, and spiral.
5. Most bacteria have a peptidoglycan cell wall; they divide by binary fission, and they may possess flagella.
6. Bacteria can use a wide range of chemical substances for their nutrition.
Archaea (p. 4)
7. Archaea consist of prokaryotic cells; they lack peptidoglycan in their cell walls.
8. Archaea include methanogens, extreme halophiles, and extreme thermophiles.
Fungi (p. 4)
9. Fungi (mushrooms, molds, and yeasts) have eukaryotic cells (cells with a true nucleus). Most fungi are multicellular. Have chitin cell wall.
10. Fungi obtain nutrients by absorbing organic material from their environment.
Protozoa (pp. 4, 6)
11. Protozoa are unicellular eukaryotes.
12. Protozoa obtain nourishment by absorption or ingestion through specialized structures. No cell wall, change shape easily (ameba).
Algae (p. 6)
13. Algae are unicellular or multicellular eukaryotes that obtain nourishment by photosynthesis. Have other plant like properties too.
14. Algae produce oxygen and carbohydrates that are used by other organisms.But have little medical importance, only one related to disease.
Viruses (p. 6)
15. Viruses are noncellular entities that are parasites of cells.
16. Viruses consist of a nucleic acid core (DNA or RNA) surrounded by a protein coat. An envelope may surround the coat.
Multicellular Animal Parasites (p. 6)
17. The principal groups of multicellular animal parasites are flatworms and roundworms, collectively called helminths.
18. The microscopic stages in the life cycle of helminths are identified by traditional microbiological procedures.
domain / Single/ multi cell / Cell wall / food / Genetic material / Living?bacteria / prokaryote / single / Y / photosynthesis or nutrients / DNA / Y
algae / eukaryote / single or multi / Y / photosynthesis / DNA / Y / Little medical relevance; important for ecosystem.
fungi / eukaryote / single or multi / Y chitin / nutrients / DNA / Y / plant like
protozoa / eukaryote / single / N / nutrients / DNA / Y / ameba
Virus (viroid, prion) / Not living / no cell / nocell / parasitic; Can’t get food on its own. / DNA or RNA / N
Classification of Microorganisms (p. 6)
19. All organisms are classified into Bacteria, Archaea, and Eukarya. Eukarya include protists, fungi, plants, and animals.
A Brief History of Microbiology (pp. 6–16)
The First Observations (p. 7)
1. Robert Hooke observed that cork was composed of “little boxes”; he introduced the term cell (1665).
2. Hooke’s observations laid the groundwork for development of the cell theory, the concept that all living things are composed of cells.
3. Anton van Leeuwenhoek, using a simple microscope, was the first to observe microorganisms (1673).
The Debate over Spontaneous Generation (p. 8)
4. Until the mid-1880s, many people believed in spontaneous generation, the idea that living organisms could arise from nonliving matter.
5. Francesco Redi demonstrated that maggots appear on decaying meat only when flies are able to lay eggs on the meat (1668).
6. John Needham claimed that microorganisms could arise spontaneously from heated nutrient broth (1745).
7. Lazzaro Spallanzani repeated Needham’s experiments and suggested that Needham’s results were due to microorganisms in the air entering his broth (1765).
8. Rudolf Virchow introduced the concept of biogenesis: living cells can arise only from preexisting cells (1858).
9. Louis Pasteur demonstrated that microorganisms are in the air everywhere and offered proof of biogenesis (1861).
10. Pasteur’s discoveries led to the development of aseptic techniques used in laboratory and medical procedures to prevent contamination by microorganisms.
11. John Tyndall arranged sealed flasks of boiled infusion in air tight box. After dusk settled and carefully opened box, the liquid remain sterile.
The Golden Age of Microbiology (pp. 9–11)
11. The science of microbiology advanced rapidly between 1857 and 1914.
Fermentation and Pasteurization (p. 9)
12. Pasteur found that yeast ferment sugars to alcohol and that bacteria can oxidize the alcohol to acetic acid, making the wine oily and sour. Later Pasteur’s contribution includes the silk worm industry, idetified 3 separate diseases caused by 3 microorganisms.
13. A heating process called pasteurization is used to kill bacteria in some alcoholic beverages and milk.
The Germ Theory of Disease (pp. 9, 11)
14. Agostino Bassi (1835) and Pasteur (1865) showed a causal relationship between microorganisms and disease.
15. Agnaz Semmelweis recognized a connection between autopsies and puereral fever due to not washing hands between the two activities. Joseph Lister introduced the use of a disinfectant to clean surgical wounds in order to control infections in humans (1860s).
16. Robert Koch proved that microorganisms cause disease. He used a sequence of procedures, now called Koch’s postulates (1876), that are used today to prove that a particular microorganism causes a particular disease.
1). The causative agent must be found in every case of the disease.
2). The disease organism must be isolated and cultured in vitro.
3). Inoculationof the same culture to healthy, susceptable animal must induce the same disease.
4). The disease organism must be isolated again from the inoculated animal.
Vaccination (p. 11)
17. In a vaccination, immunity (resistance to a particular disease) is conferred by inoculation with a vaccine.
18. In 1798, Edward Jenner demonstrated that inoculation with cowpox material provides humans with immunity to smallpox.
19. About 1880, Pasteur discovered that avirulent bacteria could be used as a vaccine for fowl cholera; he coined the word vaccine.
20. Modern vaccines are prepared from living avirulent microorganisms or killed pathogens, from isolated components of pathogens, and by recombinant DNA techniques.
21. Elie Metchinikoff discovered cellular immunity, phagocytes.
The Birth of Modern Chemotherapy: Dreams of a “Magic Bullet” (pp. 12–13)
21. Chemotherapy is the chemical treatment of a disease.
22. Two types of chemotherapeutic agents are synthetic drugs (chemically prepared in the laboratory) and antibiotics (substances produced naturally by bacteria and fungi to inhibit the growth of other microorganisms).
23. Paul Ehrlich introduced an arsenic-containing chemical called salvarsan to treat syphilis (1910).
24. Alexander Fleming observed that the Penicillium fungus inhibited the growth of a bacterial culture. He named the active ingredient penicillin (1928).
25. Penicillin has been used clinically as an antibiotic since the 1940s.
26. Researchers are tackling the problem of drug-resistant microbes.
Modern Developments in Microbiology (pp. 13–16)
27. Bacteriology is the study of bacteria, mycology is the study of fungi, and parasitology is the study of parasitic protozoa and worms.
28. Microbiologists are using genomics, the study of all of an organism’s genes, to classify bacteria, fungi, and protozoa.
29. The study of AIDS, analysis of the action of interferons, and the development of new vaccines are among the current research interests in immunology.
30. New techniques in molecular biology and electron microscopy have provided tools for advancing our knowledge of virology.
31. The development of recombinant DNA technology has helped advance all areas of microbiology.
Microbes and Human Welfare (pp. 16–18)
1. Microorganisms degrade dead plants and animals and recycle chemical elements to be used by living plants and animals.
2. Bacteria are used to decompose organic matter in sewage.
3. Bioremediation processes use bacteria to clean up toxic wastes.
4. Bacteria that cause diseases in insects are being used as biological controls of insect pests. Biological controls are specific for the pest and do not harm the environment.
5. Using microbes to make products such as foods and chemicals is called biotechnology.
6. Using recombinant DNA, bacteria can produce important substances such as proteins, vaccines, and enzymes.
7. In gene therapy, viruses are used to carry replacements for defective or missing genes into human cells.
8. Genetically modified bacteria are used in agriculture to protect plants from frost and insects and to improve the shelf life of produce.
Microbes and Human Disease (pp. 18–21)
1. Everyone has microorganisms in and on the body; these make up the normal microbiota, or flora.
2. The disease-producing properties of a species of microbe and the host’s resistance are important factors in determining whether a person will contract a disease.
3. Bacterial communities that form slimy layers on surfaces are called biofilms.
4. An infectious disease is one in which pathogens invade a susceptible host.
5. An emerging infectious disease (EID) is a new or changing disease showing an increase in incidence in the recent past or a potential to increase in the near future.
Units of Measurement (p. 55)
1. The standard unit of length is the meter (m).
2. Microorganisms are measured in micrometers, µm (10–6 m), and in nanometers, nm (10–9 m). 1m = 103 mm = 106 mm =109 nm = 1012 pm = 1015Å
Microscopy: The Instruments (p. 55)
1. A simple microscope consists of one lens; a compound microscope has multiple lenses.
Light Microscopy (pp. 56, 58–62)
Compound Light Microscopy (pp. 56, 58–59)
2. The most common microscope used in microbiology is the compound light microscope (LM).
3. The total magnification of an object is calculated by multiplying the magnification of the objective lens by the magnification of the ocular lens.
4. The compound light microscope uses visible light.
5. The maximum resolution, or resolving power (the ability to distinguish two points) of a compound light microscope is 0.2 µm; maximum magnification is 2000x.
6. Specimens are stained to increase the difference between the refractive indexes of the specimen and the medium.
7. Immersion oil is used with the oil immersion lens to reduce light loss between the slide and the lens. Refraction is the bending of light as it passes through from one medium to another of different density. The index of refraction is a measured of the speed at which light pases through the material. Immersion oil has the same index of refraction as glass, not air.
8. Brightfield illumination is used for stained smears or sections.
9. Unstained cells are more productively observed using darkfield, phase-contrast, or DIC(Differential Interference Contrast, Nomarski) microscopy.
Darkfield Microscopy (p. 59)
10. The darkfield microscope shows a light silhouette of an organism against a dark background. Light does not transmitted directly through the specimen, rather, it reflect off the specimen at an angle.
11. It is most useful for detecting the presence of extremely small organisms.
Phase-Contrast Microscopy (pp. 59–60)
12. A phase-contrast microscope brings direct and reflected or diffracted light rays together (in phase) to form an image of the specimen on the ocular lens. Has a special condemser and objective lens that accentuate the differences in the refractive index of various structures within the organism.
13. It allows the detailed observation of living organisms.
Differential Interference Contrast (DIC) Microscopy (p. 60)
14. The DIC microscope provides a colored, three-dimensional image of the object being observed. A refined phase contrast scope.
15. It allows detailed observations of living cells.
Fluorescence Microscopy (pp. 61–62)
16. In fluorescence microscopy, specimens are first stained with fluorochromes and then viewed through a compound microscope by using an ultraviolet light source.
17. The microorganisms appear as bright objects against a dark background.
18. Fluorescence microscopy is used primarily in a diagnostic procedure called fluorescent-antibody (FA) technique, or immunofluorescence.
Confocal Microscopy (p. 62)
19. In confocal microscopy, a specimen is stained with a fluorescent dye and illuminated with short-wavelength light.
20. Using a computer to process the images, two-dimensional and three-dimensional images of cells can be produced.
Two-Photon Microscopy (p. 62)
21. In TPM, a live specimen is stained with a fluorescent dye and illuminated with long-wavelength light.
Scanning Acoustic Microscopy (p. 63)
22. Scanning acoustic microscopy (SAM) is based on the interpretation of sound waves through a specimen.
23. It is used to study living cells attached to surfaces such as cancer cells, artery plaque, and biofilms.
Electron Microscopy (pp. 63–65)
24. Instead of light, a beam of electrons is used with an electron microscope. Shorter the wave length, bettr the resolution.
25. Instead of glass lenses, electromagnets control focus, illumination, and magnification.
26. Thin sections of organisms can be seen in an electron micrograph produced using a transmission electron microscope (TEM). Magnification: 10,000–100,000x. Resolving power: 2.5 nm.
27. Three-dimensional views of the surfaces of whole microorganisms can be obtained with a scanning electron microscope (SEM). Magnification: 1000–10,000x. Resolving power: 20 nm. It usually used with the freeze – fracture technique, producing a natural surface. Metal can be sparayed on.
Scanned-Probe Microscopy (p. 65)
28. Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) produce three-dimensional images of the surface of a molecule.
Preparation of Specimens for Light Microscopy (pp. 68–72)
Preparing Smears for Staining (pp. 68–69)
1. Staining means coloring a microorganism with a dye to make some structures more visible.
2. Fixing uses heat or alcohol to kill and attach microorganisms to a slide.
3. A smear is a thin film of material used for microscopic examination.
4. Bacteria are negatively charged, and the colored positive ion of a basic dye will stain bacterial cells.
5. The colored negative ion of an acidic dye will stain the background of a bacterial smear; a negative stain is produced.
Simple Stains (p. 69)
6. A simple stain is an aqueous or alcohol solution of a single basic dye.