Chapter 27Overview: They’re (Almost) Everywhere!PowerPoint PresentationConcept 27.1: Structural, functional, and genetic adaptations contribute to prokaryotic successLE 27-2Cell-Surface StructuresLE 27-3Slide 8LE 27-4Slide 10LE 27-5MotilityLE 27-6Internal and Genomic OrganizationLE 27-7Slide 16LE 27-8Slide 18Reproduction and AdaptationLE 27-9Slide 21Concept 27.2: A great diversity of nutritional and metabolic adaptations have evolved in prokaryotesSlide 23Metabolic Relationships to OxygenNitrogen MetabolismMetabolic CooperationLE 27-10Slide 28Slide 29Concept 27.3: Molecular systematics is illuminating prokaryotic phylogenyLessons from Molecular SystematicsSlide 32LE 27-12BacteriaLE 27-13ArchaeaSlide 37Slide 38Slide 39Slide 40Concept 27.4: Prokaryotes play crucial roles in the biosphereChemical RecyclingSymbiotic RelationshipsSlide 44Concept 27.5: Prokaryotes have both harmful and beneficial impacts on humansPathogenic ProkaryotesSlide 47Slide 48Prokaryotes in Research and TechnologySlide 50Slide 51Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures for Biology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris RomeroChapter 27Chapter 27ProkaryotesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOverview: They’re (Almost) Everywhere!•Most prokaryotes are microscopic, but what they lack in size they make up for in numbers•There are more in a handful of fertile soil than the number of people who ever lived•Prokaryotes thrive almost everywhere, including places too acidic, too salty, too cold, or too hot for most other organisms•They have an astonishing genetic diversityCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 27.1: Structural, functional, and genetic adaptations contribute to prokaryotic success•Most prokaryotes are unicellular, although some species form colonies•Prokaryotic cells have a variety of shapes•The three most common of which are spheres (cocci), rods (bacilli), and spiralsVideo: TubewormsVideo: TubewormsLE 27-2LE 27-2Spherical (cocci)Rod-shaped (bacilli)Spiral5 µm2 µm1 µmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCell-Surface Structures•An important feature of nearly all prokaryotic cells is their cell wall, which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment•Using the Gram stain, scientists classify many bacterial species into groups based on cell wall composition, Gram-positive and Gram-negativeLE 27-3LE 27-3PepridoglycanlayerCell wallProteinGram-positivebacteriaGram-positiveGram-negativeGram-negativebacteriaPepridoglycanlayerCell wallPlasma membraneLipopolysaccharidePlasma membraneProteinOutermembrane20 µmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•The cell wall of many prokaryotes is covered by a capsule, a sticky layer of polysaccharide or proteinLE 27-4LE 27-4Capsule200 nmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•Some prokaryotes have fimbriae and pili, which allow them to stick to their substrate or other individuals in a colonyLE 27-5LE 27-5Fimbriae200 nmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMotility•Most motile bacteria propel themselves by flagella that are structurally and functionally different from eukaryotic flagella•In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuliVideo: Prokaryotic Flagella Video: Prokaryotic Flagella (Salmonella (Salmonella typhimuriumtyphimurium))LE 27-6LE 27-6FlagellumFilamentCell wallHookBasal apparatusPlasmamembrane50 nmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsInternal and Genomic Organization•Prokaryotic cells usually lack complex compartmentalization•Some prokaryotes do have specialized membranes that perform metabolic functionsLE 27-7LE 27-7ThylakoidmembranesRespiratorymembranePhotosynthetic prokaryoteAerobic prokaryote0.2 µm1 µmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•The typical prokaryotic genome is a ring of DNA that is not surrounded by a membrane and that is located in a nucleoid regionLE 27-8LE 27-8Chromosome1 µmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•Some species of bacteria also have smaller rings of DNA called plasmidsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsReproduction and Adaptation•Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours•Many prokaryotes form endospores, which can remain viable in harsh conditions for centuriesLE 27-9LE 27-9Endospore0.3 µmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•Rapid reproduction and horizontal gene transfer facilitate the evolution of prokaryotes in changing environmentsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 27.2: A great diversity of nutritional and metabolic adaptations have evolved in prokaryotes•All four models of nutrition are found among prokaryotes:–Photoautotrophy–Chemoautotrophy–Photoheterotrophy–ChemoheterotrophyCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMetabolic Relationships to Oxygen•Prokaryotic metabolism varies with respect to oxygen:–Obligate aerobes require oxygen–Facultative anaerobes can survive with or without oxygen–Obligate anaerobes are poisoned by oxygenCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsNitrogen Metabolism•Prokaryotes can metabolize nitrogen in a variety of ways•In nitrogen fixation, some prokaryotes convert atmospheric nitrogen to ammoniaCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMetabolic Cooperation•Cooperation between prokaryotes allows them to use environmental resources they could not use as individual cells•In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells exchange metabolic productsVideo: Video: CyanobacteriaCyanobacteria ((OscillatoriaOscillatoria))LE 27-10LE 27-10HeterocytePhotosyntheticcells20 µmCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•In some prokaryotic species,