BIO 203 Lecture 2 Microbes in our lives reading.tiff

BIO 203 Lecture 2 Microbes in our lives reading.tiff - PART...

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Unformatted text preview: PART ONE Fundamentals ofMicrobioJogy Microbes in Our Lives LEARNING OBJECTIVE 1-1 List several ways in which microbes affect our lives. For many people, the words germ and microbe bring to mind a group of tiny creatures that do not quite fit into any of the cat« egories in that old question, “Is it animal, vegetable, or mineral?” Microbes, also called microorganisms, are minute living things that individually are usually too small to be seen with the un- aided eye. The group includes bacteria, fungi (yeasts and molds), protozoa, and microscopic algae. It also includes viruses, those noncellular entities sometimes regarded as straddling the border between life and nonlife (Chapters 11, 12, and 13, respectively). We tend to associate these small organisms only with un— comfortable infections, with common inconveniences such as spoiled food, or with major diseases such as AIDS. However, the majority of microorganisms actually help maintain the balance of life in our environment. Marine and freshwater microorgan- isms form the basis of the food chain in oceans, lakes, and rivers. Soil microbes help break down wastes and incorporate nitrogen gas from the air into organic compounds, thereby recycling chemical elements among soil, water, living organisms, and air. Certain microbes play important roles in photosynthesis, a food- and oxygen—generating process that is critical to life on Earth. Humans and many other animals depend on the microbes in their intestines for digestion and the synthesis of some vitamins that their bodies require, including some B vitamins for metab- olism and vitamin K for blood clotting. Microorganisms also have many commercial applications. They are used in the synthesis of such chemical, products as vitamins, organic acids, enzymes, alcohols, and many drugs. For example, microbes are used to produce acetone and buta- nol, and the vitamins B2 (riboflavin) and B12 (cobalamin) are made biochemically. The process by which microbes produce acetone and butanol was discovered in 1914 by Chaim Weiz— mann, a Russian-born chemist working in England. With the outbreak of World War I in August of that year, the produc- tion of acetone became very important for making cordite (a smokeless form of gunpowder used in munitions). Weizmann’s discovery played a significant role in determining the outcome of the war. The food industry also uses microbes in producing, for example, vinegar, sauerkraut, pickles, soy sauce, cheese, yogurt, bread, and alcoholic beverages. In addition, enzymes from mi~ crobes can nowbe manipulated to cause the microbes to produce substances they normally don’t synthesize, including cellulose, digestive aids, and drain cleaner, plus important therapeutic substances such as insulin. Microbial enzymes may even have helped produce your favorite pair of jeans (see the Applications of Microbiology box). Though only a minority of microorganisms are pathogenic (diseaseaproducing), practical knowledge of microbes is necessary for medicine and the related health sciences. For exampi hospital workers must be able to protect patients from comm: microbes that are normally harmless but pose a threat to the sic and injured. Today we understand that microorganisms are found almo everywhere. Yet not long ago, before the invention of the mien scope, microbes were unknown to scientists. Thousands of per ple died in devastating epidemics, the causes’and transmissic of which were not understood. Entire families died because Val cinations and antibiotics were not available to fight infections. We can get an idea of how our current concepts of microb ology developed by looking at a few historic milestones in m crobiology that have changed our lives. First, however, we wi look at the major groups of microbes and how they are name and classified. MINE UNDERSTANDING W Describe some of the destructive and beneficial actions of microbes. 1-]* Naming (and Classifying Microorganisms LEARNING OBJECTIVES 1-2 Recognize the system of scientific nomenclature that uses two names: a genus and a specific epithet. 1—3 Differentiate the major characteristics of each group of microorganisms. 1-4 List the three domains. Nomenclature The system of nomenclature (naming) for organisms in us: today was established in 1735 by Carolus Linnaeus. -Scientifi< names are latinized because Latin was the language tradition ally used by scholars. Scientific nomenclature assigns each or ganism two names—the genus (plural: genera) is the first name and is always capitalized; the specific epithet (species name: follows and is not capitalized. The organism is referred to by both the genus and the specific epithet, and both names are underlined or italicized. By custom, after a scientific name has been mentioned once, it can be abbreviated with the initial oi the genus followed by the specific epithet. Scientific names can, among other things, describe an 01—. ganism, honor a researcher, or identify the habitat of a species. For example, consider Staphylococcus aureus, a bacterium com— monly found on human skin. Staphylm describes the clustered arrangement of the cells; -coccus indicates that they are shaped like spheres. The specific epithet, omens, is Latin for golden, *The numbers following Check Your Understanding questions refer to the corre- sponding Learning Objectives. ...
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