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Prokaryotes Chapter 27 Slide 2 Earliest organisms on Earth - evolved alone for 1.5 billion years. More prokaryotes inhabit a handful of fertile soil or the mouth or skin of a human than the total number of people who have ever lived. Slide 3 The vivid reds, oranges, and yellows that paint these rocks are colonies of prokaryotes. Slide 4 Types of diseases caused by bacteria - tuberculosis, cholera, many sexually transmissible diseases, certain types of food poisoning. Slide 5 http://news.bbc.co.uk/olmedia/1825000/images/_1827130_tb_bacterium300.jpg TB Bacteria Slide 6 Most bacteria benign or beneficial. Bacteria in intestines produce vitamins. Prokaryotes recycle carbon, other elements between soil and atmosphere. Slide 7 Slide 8 Mitochondria, chloroplasts evolved from prokaryotes - became residents in host cells. Slide 9 http://www.botany.hawaii.edu/faculty/webb/Bot201/Hornworts/AnthEpiSurfCplast.jpg Slide 10 2 prokaryotic domains (above kingdom): Bacteria and Archaea Archaea inhabit extreme environments - differ from bacteria in structural, biochemical, and physiological characteristics. Slide 11 Slide 12 Most prokaryotes - unicellular. Some aggregate for period of time or form colonies. Shapes - spheres (cocci), rods (bacilli), helices (spirochetes). Slide 13 Slide 14 Cell wall maintains shape, physical protection, prevents cell from bursting. Most bacterial cell walls contain peptidoglycan, (polymer of sugars and polypeptides) Archaea lack peptidoglycan. Slide 15 http://msnbcmedia3.msn.com/j/msnbc/Components/Photos/050207/050207_livesci_extremophiles_hmed11a.hlarge.jpg Slide 16 Gram stain - identifies bacteria based on differences in cell walls. Gram + have simpler cell walls, large amounts of peptidoglycans. Slide 17 Slide 18 Gram - have more complex cell walls, less peptidoglycan - outer membrane contains carbohydrates bonded to lipids. More threatening than gram- positive species. Slide 19 Slide 20 Gram-negative bacteria more resistant to antibiotics - outer membrane impedes entry of antibiotics. Slide 21 http://jon9783.myweb.uga.edu/image/image1.jpg E. coli Slide 22 Many prokaryotes secrete sticky protective layer - capsule. Glue together cells of prokaryotes that live as colonies. Slide 23 http://www.olympusmicro.com/micd/galleries/darkfield/bacterialcapsules.html Slide 24 Pili fastens pathogenic bacteria to mucous membranes of host. Some specialized for holding 2 prokaryote cells together to transfer DNA during conjugation. Slide 25 Slide 26 Most common form of movement - flagella. 2 nd found in spirochetes - filaments - moves like a corkscrew. 3 rd occurs in cells that secrete slimy threads - glides along at growing end of threads. Slide 27 Slide 28 Capable of taxis (chemotaxis, phototaxis) Slide 29 http://www.brineshrimpdirect.com/contentimages/brineshrimp_photo3.jpg Slide 30 Prokaryotic cells lack nucleus, internal compartments bounded by membranes like eukaryotes. Use infolded regions of plasma membrane to perform metabolic functions (cellular respiration, photosynthesis) Slide 31 Slide 32 Simpler genomes than eukaryotes - DNA concentrated as fibers in nucleoid region. Single prokaryotic chromosome - double-stranded DNA molecule in form of ring. May also have smaller rings of DNA (plasmids) consist of only a few genes. Slide 33 http://student.biology.arizona.edu/honors2000/group10/ plasmid.gif Slide 34 Prokaryotes reproduce asexually - binary fission. Transformation - cell can absorb, integrate fragments of DNA from environment. Conjugation - directly transfers genes to another cell. Transduction - viruses transfer genes between prokaryotes. Slide 35 Slide 36 Prokaryote can withstand harsh conditions. Bacteria form resistant cells - endospores - cell replicates chromosome, surrounds one chromosome with durable wall. Can survive lack of nutrients and water, extreme heat or cold, and most poisons. Slide 37 http://www.apsnet.org/education/illustratedglossary/PhotosE-H/endospore.jpg Slide 38 When conditions favorable - hydrates and becomes active. Microorganisms release antibiotics to inhibit growth of other microorganisms (prokaryotes, protists, and fungi) because of competition for space. Humans use these to kill bacteria. Slide 39 http://www.lausd.k12.ca.us/Figueroa_EL/images/Mystery%20to%20Medicine/antibiotics.jpg Slide 40 Prokaryotes grouped according to how they obtain nutrition. 1 Light energy - phototrophs. 2 Energy from chemicals in environment -chemotrophs. 3 Need only CO 2 as carbon source - autotrophs. 4 Require organic nutrient as carbon source - heterotrophs. Slide 41 http://www.clcbio.com/scienceimages/cyanobacteria.png Slide 42 Further divided based on what they use. 1 Photoautotrophs - photosynthetic - light energy to synthesize organic compounds from CO 2. Photoautotrophic prokaryotes - cyanobacteria. Photosynthetic eukaryotes - plants and algae. Slide 43 http://www.astrographics.com/GalleryPrints/Display/GP 2028.jpg Slide 44 2 Chemoautotrophs need CO 2 as carbon source, obtain energy by oxidizing inorganic substances, not light - i.e. hydrogen sulfide (H 2 S), ammonia (NH 3 ) Unique to prokaryotes. 3 Photoheterotrophs - light to generate ATP, obtain carbon in organic form. Restricted to prokaryotes. Slide 45 http://www.theguardians.com/Microbiology/lyngb3_bg.jpg Slide 46 4 Chemoheterotrophs must consume organic molecules for energy and carbon. Found in prokaryotes, protists, fungi, animals, and even some parasitic plants. Majority of prokaryotes - chemoheterotrophs. Include saprobes (decomposers) and parasites. Slide 47 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Slide 48 O 2 also has impact. Obligate aerobes require O 2 for respiration. Facultative anerobes will use O 2 if present; can also grow by fermentation in anaerobic environment. Obligate anaerobes are poisoned by O 2 use either fermentation or anaerobic respiration. Slide 49 http://www.medschool.lsuhsc.edu/microbiology/DMIP/cpgs.jpg Slide 50 1 st prokaryotes - heterotrophic - fed on primordial soup - depleted supply of organic molecules in environment. Natural selection favored prokaryote that could harness energy of sunlight make ATP. Photosynthesis probably evolved once and was lost by heterotrophs. Slide 51 http://www.multihostingservice.co.uk/teamanarchy/simo n/images/Sporesom4.jpg Slide 52 Atmosphere transformed from reducing one to oxidizing one by evolution of cyanobacteria. Cellular respiration probably evolved by modification of photosynthetic equipment for new function (both use electron transport chain). Slide 53 http://www.mfe.govt.nz/publications/ser/snapshot-lake- water-quality-nov06/html/images/cyanobacteria.jpg Slide 54 Survey of Prokaryotes Archaea - extremophiles, lovers of extreme environments. 1 Methanogens - obtain energy by using CO 2 to oxidize H 2 replacing methane as waste - live in swamps and marshes, guts of animals. May contribute to global warming. Slide 55 http://genome.jgi-psf.org/finished_microbes/images/metba.gif Slide 56 2 Extreme halophiles - saline places - Great Salt Lake, Dead Sea. Colonies form purple-red scum from photosynthetic pigment similar to pigment found in human retina. Slide 57 Slide 58 3 Extreme thermophiles - hot environments - optimum temperatures for most - 60 o C-80 o C. One sulfur-metabolizing thermophile lives at 105 o C water near deep-sea hydrothermal vents. Slide 59 http://www.ls.toyaku.ac.jp/~lcb-7/images/hydrothermalvent.jpg Slide 60 Why important? Decomposers - important to nutrient recycling. Nitrogen fixation - important to nitrogen cycle. Many - symbiotic - involved in mutual relationship with host - i.e. - fish provides bioluminescent bacteria under eye with organic materials uses flashlight to lure prey, signal potential mates. Slide 61 Slide 62 Most of the time our defenses check growth of pathogens. Pathogenic prokaryotes cause half of all human disease when internal defenses cannot fight them off. Slide 63 Slide 64 Some pathogens - opportunistic (always in our system) - attack only when defenses down. Robert Koch 1 st to connect certain diseases to specific bacteria - established Kochs postulates. Ensures that pathogen really is causing the disease. Slide 65 http://upload.wikimedia.org/wikipedia/commons/thumb/6 /67/Escherichia_Coli_NIAID.jpg/180px- Escherichia_Coli_NIAID.jpg Slide 66 Pathogens can cause illness by producing poisons - exotoxins and endotoxins. Exotoxins are proteins secreted by prokaryotes - can produce disease symptoms even if prokaryote not present. Endotoxins - components of outer membranes of some gram-negative bacteria. Common in food poisoning. Slide 67 Slide 68 Disease control mostly due to education, not to expansion of drugs. Overuse of antibiotics has led to evolution of new strains of bacteria. Biological warfare also still a threat. Humans use prokaryotes to treat biological issues, such as oil spills. Slide 69 Slide 70