Chapter 16 - 16 Evolution of Microbial Life C H AP T E R O...

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head tail DNA cytoplasm of bacterium When T2 virus infect bacteria only DNA enters. CHAPTER OUTLINE Viruses Reproduce in Living Cells 16.1 Viruses have a simple structure 310 16.2 Some viruses reproduce inside bacteria 311 16.3 Viruses are responsible for a number of plant diseases 312 16.4 Viruses also reproduce inside animal cells and cause animal diseases 314 16.5 HIV (the AIDS virus) exemplifies retroviruses 315 The First Cells Originated on Early Earth 16.6 Experiments show how small organic molecules may have first formed 317 16.7 RNA may have been the first polymer 318 16.8 Protocells preceded the first true cells 319 Both Bacteria and Archaea Are Prokaryotes 16.9 Prokaryotes have unique structural features 320 16.10 Prokaryotes reproduce by binary fi ssion 321 16.11 How genes are transferred between bacteria 322 16.12 Prokaryotes have various means of nutrition 323 16.13 The cyanobacteria are ecologically important organisms 324 16.14 Some archaea live in extreme environments 325 16.15 Prokaryotes have medical and environmental importance 326 APPLICATIONS HOW BIOLOGY IMPACTS OUR LIVES Humans Suffer from Emergent Viral Diseases 313 HOW LIFE CHANGES Viruses and the Invention of DNA 316 HOW BIOLOGY IMPACTS OUR LIVES Why Can You Catch Gonorrhea Over and Over Again? 327 HOW BIOLOGY IMPACTS OUR LIVES Disease-causing Microbes Can Be Biological Weapons 328 16 Evolution of Microbial Life At Your Service: Viruses and Bacteria V iruses are noncellular entities responsible for a number of diseases in plants, animals, and humans. In humans, for example, polio, smallpox, cervical cancer, and AIDS are all caused by viruses. Even so, viruses are useful tools in the bio- technology laboratory. The fi rst investigators to show that DNA is the genetic material radioactively labeled a T2 virus before allowing it to infect bacteria. Only viral DNA entered the bac- teria, but many complete viruses emerged. Today, recombinant viruses are used to store the genes of eukaryotic organisms. When a researcher wants to work with a particular gene, she or he selects a virus containing that gene, much as you would go to the library and choose a book con- taining an item of interest. Gene therapy also uses viruses to carry normal genes into the genomes of people with genetic disorders. Bacteria and archaea are prokaryotes, organisms that are simple in structure but metabolically diverse. They can live under conditions that are too hot, too salty, too acidic, or too cold for eukaryotes. Through their ability to oxidize sulfi des that spew forth from deep-sea vents and subsequently produce nutrients, they support communities of organisms in habitats where the sun never shines. Bacteria, but not archaea, also cause diseases, such as chla- mydia, strep throat, food poi- soning, and anthrax. 308
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Syphilis bacteria , T. pallidum Ebola virus Escherichia coli, an intestinal bacterium Anthrax bacteria, Bacillus anthracis Nodules where bacteria fix nitrogen SARS virus budding from cell Bioremediation of an oil spill before after Sewage treatment plant How are bacteria of service to humankind? Both on land and in the sea, bacteria are
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