Chapter 28 – Bacteria and ArchaeaSlide 2Slide 3Slide 4Slide 5The Biological Impact of Bacteria and ArchaeaSlide 7The Abundance of ProkaryotesSome Bacteria Cause DiseaseKoch’s PostulatesSlide 11What Makes Some Bacterial Cells Pathogenic?The Past, Present, and Future of AntibioticsBacteria’s Role in BioremediationSlide 15ExtremophilesUsing Enrichment CulturesUsing Direct SequencingEvaluating Molecular PhylogeniesThe Universal TreeThemes in the Diversification of Bacteria and ArchaeaMorphological DiversitySlide 23Cell Wall CompositionGram-Positive and Gram-Negative BacteriaSlide 26Slide 27Slide 28Producing ATP via Cellular RespirationProducing ATP via FermentationProducing ATP via PhotosynthesisNitrogen Fixation and the Nitrogen CycleSlide 33Summary of Prokaryotic DiversitySlide 35Slide 36Chapter 35 - VirusesIntroductionSlide 39Why Do Biologists Study Viruses?Recent Viral Epidemics in HumansHow Do Biologists Study Viruses?Slide 43Slide 44Slide 45Analyzing Morphological TraitsSlide 47Replicative and Latent GrowthSlide 49Slide 50Slide 51Slide 52How Do Viruses Copy Their Genomes?Slide 54Exiting an Infected CellSlide 56How Are Viruses Transmitted to New Hosts?Themes in the Diversification of VirusesSlide 59Slide 60© 2011 Pearson Education, Inc.Chapter 28 – Bacteria and Archaea© 2011 Pearson Education, Inc.•What organisms are most numerous on Earth?1. Eukaryotes2. Prokaryotes© 2011 Pearson Education, Inc.•What organisms are most numerous on Earth?1. Eukaryotes2. Prokaryotes© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.The Biological Impact of Bacteria and ArchaeaThe lineages in the domains Bacteria and Archaea are ancient, diverse, abundant, and ubiquitous.•The oldest fossils found thus far are of 3.5-billion-year-old bacteria. Eukaryotes do not appear in the fossil record until 1.7 billion years later.© 2011 Pearson Education, Inc.The Biological Impact of Bacteria and Archaea•Only 5000 species of bacteria and archaea have been named and described, but biologists are virtually certain that millions exist.–Over 400 species live in the human digestive tract.–About 128 species live in the lining of the human stomach.–Approximately 500 species live in the human mouth.•Microbiology is the study of microbes, microscopic organisms.© 2011 Pearson Education, Inc.The Abundance of Prokaryotes•About 1013 cells make up your body, but living on it are about 1012 bacterial cells on your skin, and about 1014 bacterial and archaeal cells in your digestive tract.•A teaspoon of soil contains billions of microbes.•Current estimates place the number of living prokaryotes at over 5 x 1030—lined end-to-end they would stretch longer than the Milky Way!© 2011 Pearson Education, Inc.Some Bacteria Cause Disease•An infectious disease is one spread by being passed from an infected individual to an uninfected individual. •Bacteria that cause disease are said to be pathogenic.–Only a tiny fraction of the bacterial species living on and in the human body is pathogenic.•The experiments of Robert Koch in the late 1800s became the basis for the germ theory of disease, which holds that infectious diseases are caused by bacteria and viruses (acellular particles that parasitize cells).–Koch’s postulates confirm a causative link between a specific infectious disease and a specific microbe:© 2011 Pearson Education, Inc.Koch’s Postulates 1. The microbe must be present in individuals suffering from the disease and absent from healthy individuals.2. The organism must be isolated and grown in a pure culture away from the host organism.3. If organisms from the pure culture are injected into a healthy experimental animal, the disease symptoms should appear.4. The organism should be isolated from the diseased experimental animal, again grown in pure culture, and demonstrated to be the same as the original organism.© 2011 Pearson Education, Inc.Some Bacteria Cause Disease•In industrialized countries, improvements in sanitation and nutrition have dramatically reduced mortality rates due to infectious diseases since 1900.–Most of the decline in deaths due to infectious diseases occurred before the introduction of antibiotics.© 2011 Pearson Education, Inc.What Makes Some Bacterial Cells Pathogenic?•Virulence, or the ability to cause disease, is a heritable trait that varies among individuals in a population.•Some species have both pathogenic virulent strains and harmless strains.–In Escherichia coli, for example, the virulence of the strain depends upon the length of the genome and the toxicity of the resulting proteins.© 2011 Pearson Education, Inc.The Past, Present, and Future of Antibiotics•The discovery of antibiotics (molecules that kill bacteria) in 1928 and their widespread use starting in the 1940s allowed physicians to effectively combat most bacterial infections.•However, overuse of antibiotics since the late twentieth century has lead to antibiotic-resistant strains of bacteria.file:///Users/ericarowe/Documents/UTK%20Biology/UTK%20Bio140%20Fall%202011/Chapter_28/A_PowerPoint_Lecture_Tools/28_Lecture_Outline/Antibiotic_resistance.html© 2011 Pearson Education, Inc.Bacteria’s Role in Bioremediation•Some of the most serious pollutants in soils, rivers, and ponds consist of organic solvents or fuels that leaked or were spilled into the environment.•These pollutants are toxic, do not dissolve in water, and accumulate in sediments.•Bioremediation is the use of bacteria and archaea to degrade pollutants.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Extremophiles•Bacteria or archaea that live in high-salt, high-temperature, low-temperature, or high-pressure habitats are called extremophiles. •Extremophiles have become a hot area of research for several reasons:1. Understanding extremophiles may help explain how life on Earth began. 2. Astrobiologists use extremophiles as model organisms in the search for extraterrestrial life.3. Enzymes that function at extreme temperatures and pressures are useful in industrial processes, such as the use of Taq polymerase in PCR.© 2011 Pearson Education, Inc.Using Enrichment Cultures•One classical technique for isolating new types of bacteria and archaea is the use of enrichment cultures.•In this process, cells are sampled from the environment and grown under specific conditions. These enrichment cultures are based on establishing a specific set of