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Part I INTRODUCTION TO MICROBIOLOGY 1 The Evolution of Microorganisms and Microbiology CHAPTER OVERVIEW This chapter introduces the field of microbiology and discusses the importance of microorganisms not only as causative agents of disease, but also as important contributors to food production, antibiotic manufacture, vaccine development, and environmental management. It presents a brief history of the science of microbiology and an overview of the microbial world. The origin of life and microbial evolution is put in the context of microbial phylogenies. CHAPTER OBJECTIVES After reading this chapter you should be able to: define the science of microbiology and describe some of the general methods used in the study of microorganisms discuss the historical concept of spontaneous generation and the experiments that were performed to disprove this erroneous idea discuss how Koch’s postulates are used to establish the causal link between a suspected microorganism and a disease describe some of the various activities of microorganisms that are beneficial to humans describe prokaryotic and eukaryotic morphology and the distribution of microorganisms among the three domains in which living organisms are categorized discuss the origin of life, the RNA world, and the evolution of microorganisms CHAPTER OUTLINE I. Microbiology Introduction A. Microbes are found everywhere and are indispensable for cycling of essential elements on earth B. Most microbes are beneficial to society by producing foods, oxygen, and commercial products, and by enhancing human health; some microbes cause disease II.Members of the Microbial World A. Microbiology is the study of organisms too small to be clearly seen by the unaided eye (i.e., microorganisms); these include viruses, bacteria, archaea, protozoa, algae, and fungi B. Some microbes (e.g., algae and fungi) are large enough to be visible, but are still included in the field of microbiology; while these may be multicellular organisms, differentiated tissues are absent C. Prokaryotes have a relatively simple morphology and lack a true membrane-delimited nucleus D. Eukaryotes are morphologically complex and have a true, membrane-enclosed nucleus E. The work of Carl Woese and his collaborators suggests that organisms fall into one of three domains based on nucleotide sequence similarities among small subunit ribosomal RNAs (SSU rRNAs) 1. Eukarya —contains all eukaryotic organisms; have a complex membrane-delimited organelle structure 2. Bacteria —diverse and widespread prokaryotes; cell walls contain peptidoglycan 3. Archaea —prokaryotes with cell walls that lack peptidoglycan; have unique membrane lipids 1
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F. Viruses, viroids, virusoids, and prions are not composed of cells and not part of the domain classification scheme III. Microbial Evolution A. Evidence for the origin of life 1. Earth is about 4.6 billion years old; what appear to be the fossilized remains of 3.5-billion- year-old prokaryotic cells have been found in stromatolites and sedimentary rocks
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This note was uploaded on 05/02/2011 for the course BIOL 2051 taught by Professor Brininstool during the Spring '07 term at LSU.

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