
<p>2/4/15 </p><p>Prokaryotes <br>(Domains Bacteria & Archaea) <br>KEY POINTS </p><p>1.ꢀ Decomposers: recycle organic and inorganic molecules in environment; makes them available to other organisms. <br>2.ꢀ Essential components of symbioses. 3.ꢀ Encompasses the origins of metabolism and metabolic diversity. <br>4.ꢀ Origin of photosynthesis and formation of atmospheric Oxygen </p><p><strong>Humans </strong></p><p>ANTIQUITY </p><p><strong>Colonization of land </strong></p><p><strong>Animals </strong><br><strong>Origin of solar </strong></p><p><strong>system and Earth </strong></p><p>•ꢀ >3.5 BILLION years old. <br>•ꢀ Alone for 2 </p><p><strong>1</strong><br><strong>4</strong></p><p>billion years </p><p><strong>Proterozoic Archaean </strong><br><strong>Prokaryotes </strong></p><p></p><ul style="display: flex;"><li style="flex:1"><strong>2</strong></li><li style="flex:1"><strong>3</strong></li></ul><p><strong>Multicellular eukaryotes </strong></p><p><strong>Single-celled eukaryotes </strong><br><strong>Atmospheric oxygen </strong></p><p>General characteristics </p><p>1.ꢀ Small: compare to <br>10-100µm for eukaryotic cell; single-celled; may form colonies. <br>2.ꢀ Lack membraneenclosed organelles. <br>3.ꢀ Cell wall present, <em>but </em></p><p><em>different from plant cell wall</em>. </p><p>1<br>2/4/15 </p><p>General characteristics </p><p>4.ꢀ Occur everywhere, most numerous organisms. </p><p>–ꢀ More individuals in a handful of soil then there are people that </p><p><em>have ever lived</em>. </p><p>–ꢀ By far more individuals in our gut than eukaryotic cells that are actually us. </p><p>General characteristics </p><p>5.ꢀ Metabolic diversity established nutritional modes of eukaryotes. </p><p>General characteristics </p><p>6.ꢀ Important decomposers and recyclers </p><p>2<br>2/4/15 </p><p>General characteristics </p><p>6.ꢀ Important decomposers and recyclers </p><p>•ꢀ Form the basis of </p><p><strong>global nutrient cycles</strong>. </p><p>General characteristics </p><p><strong>7. Symbionts</strong>!!!!!!! </p><p>•ꢀ <strong>Parasites </strong></p><p>•ꢀ Pathogenic organisms. <br>•ꢀ About 1/2 of all human diseases are caused by Bacteria </p><p>General characteristics </p><p><strong>7. Symbionts</strong>!!!!!!! </p><p>•ꢀ <strong>Parasites </strong></p><p>•ꢀ Pathogenic organisms. <br>•ꢀ Extremely important in agriculture as well. </p><p>Pierce’s disease is caused by <em>Xylella fastidiosa</em>, a Gamma Proteobacteria. It causes over $56 million in damage annually in California. That’s with $34 million spent to control it! = $90 million in California alone. </p><p>3<br>2/4/15 </p><p>General characteristics </p><p><strong>7. Symbionts</strong>!!!!!!! </p><p>•ꢀ <strong>Commensalists </strong></p><p>•ꢀ They are everywhere (really). <br>•ꢀ There can be 10 million cells per square centimeter of skin. </p><p>General characteristics </p><p><strong>7. Symbionts</strong>!!!!!!! </p><p>•ꢀ <strong>Mutualists </strong></p><p>•ꢀ Eukaryotic life would be impossible without this. </p><p>General characteristics </p><p><strong>7. Symbionts</strong>!!!!!!! </p><p>•ꢀ <strong>Mutualists </strong></p><p>•ꢀ Allows herbivorous <br>(plant-feeding) animals to digest cellulose and other low-quality plant tissues. <br>•ꢀ Termites •ꢀ Ungulates “chewing the cud” <br>•ꢀ Lagomorph coprophagy </p><p>4<br>2/4/15 </p><p>General characteristics </p><p><strong>7. Symbionts</strong>!!!!!!! </p><p>•ꢀ <strong>Mutualists </strong></p><p>•ꢀ Mealybug endosymbionts with endosymbionts. </p><p>General characteristics </p><p><strong>7. Symbionts</strong>!!!!!!! </p><p>•ꢀ <strong>Mutualists </strong></p><p>•ꢀ Komodo dragons and their <br>“toxins”. <br>•ꢀ Hunt large prey and can inflict fairly minor wound. <br>•ꢀ Prey die fairly quickly from wound. <br>•ꢀ Infection by highly pathogenic </p><p><em>Pasteurella multocida </em>(Gamma </p><p>Proteobacteria). <br>•ꢀ Prominent in saliva of dragons, but dragons have an anti- </p><p><em>Pasteurella </em>antibody. </p><p>TAXONOMY is problematic </p><p>•ꢀ Relationships obscured by billions of years of evolution <br>•ꢀ Also obscured by unique bacterial means of recombination (more later). <br>•ꢀ Grouped primarily by DNA sequence data. <br>•ꢀ Immense genetic/genomic diversity. </p><p>5<br>2/4/15 </p><p>Current taxonomy is stabilizing </p><p>•ꢀ Note that “Prokaryote” is paraphyletic<em>. </em>Why? <br>•ꢀ Two Domains: </p><p>•ꢀ <strong>Archaea</strong>: extremophiles </p><p>(mostly), ancient, probable progenitors of eukaryotes. </p><p>•ꢀ <strong>Bacteria</strong>: most </p><p>commonly-encountered prokaryotes. </p><p>Characteristics </p><p>•ꢀ Cell Surface •ꢀ Motility •ꢀ Genome •ꢀ Reproduction & Growth •ꢀ Metabolic Diversity •ꢀ Nitrogen Metabolism •ꢀ Oxygen Relationships </p><p>Cell Surface </p><p>•ꢀ <strong>Archaea</strong>: plasma </p><p>membrane of </p><p><em>ether-</em>lipids </p><p>(unique in life). </p><p>•ꢀ <strong>Bacteria</strong>: a sugar </p><p>polymer - </p><p><em>peptidoglycan </em></p><p>6<br>2/4/15 </p><p>Cell Surface </p><p>•ꢀ Cell wall is often modified with structures to adhere to substrate. <br>•ꢀ Many secrete a sticky capsule or adhere by fimbriae (ocasionally called pili). </p><p>Motility </p><p>•ꢀ ~half the species can move. 1.ꢀ Flagella most common </p><p>(<em>different </em>structure from </p><p>eukaryote) <br>2.ꢀ Spiral filaments: spirochetes corkscrew <br>3.ꢀ Gliding over slimy secretions <br>(via flagellar motors without filament) </p><p>•ꢀ Capable of <strong>taxis </strong>(photo, </p><p>chemo, geo, etc.) </p><p>Genome </p><p>•ꢀ Small genomes: <br>~1/1000th DNA content of eukaryotes. <br>•ꢀ No membrane enclosed nucleus. <br>•ꢀ DNA concentrated in <br>‘nucleoid’ region. </p><p>7<br>2/4/15 </p><p>Genome </p><p>•ꢀ One major chromosome, double stranded DNA molecule in ring. <br>•ꢀ Sometimes several small DNA rings of few genes: </p><p><strong>plasmids. </strong></p><p>–ꢀ Replicate independently of main chromosome. <br>–ꢀ Permit recombination via </p><p><strong>conjugation </strong>(later). </p><p>–ꢀ Involved in resistance to antibodies/antibiotics. </p><p>Genome </p><p>•ꢀ Broadly, replication & translation of genetic info like that of eukaryotes; differ in details and simplicity. <br>•ꢀ Used in first DNA recombinant research. </p><p>•ꢀ <strong>Genetic recombination</strong>: Not like eukaryotes </p><p>(e.g. chiasma & crossing over)!! </p><p>–ꢀ <strong>Transformation </strong>–ꢀ <strong>Conjugation </strong>–ꢀ <strong>Transduction </strong></p><p>Genome: Recombination via transformation </p><p>•ꢀ DNA taken up from the environment </p><p>8<br>2/4/15 </p><p>Genome: Recombination via conjugation </p><p>•ꢀ Direct transfer of DNA between cells. <br>•ꢀ Both plasmids and </p><p><em>portions </em>of bacterial </p><p>chromosome. </p><p>Genome: Recombination via transduction </p><p>•ꢀ Transfer of DNA via </p><p><strong>phage viruses</strong>. </p><p>Reproduction & Growth </p><p>•ꢀ Meiosis & Mitosis NOT PRESENT. </p><p>•ꢀ <strong>Asexual binary fission. </strong></p><p>•ꢀ DNA replication can be nearly continuous in ideal conditions (depends on pH, salinity, temperature, etc.) <br>•ꢀ Generation times as fast as 20 minutes </p><p>9<br>2/4/15 </p><p>Metabolism </p><p>Metabolic Diversity </p><p>•ꢀ Nutrition: </p><p>•ꢀ Requires a <strong>source of carbon </strong>for </p><p>synthesizing organic compounds: either carbon dioxide or living matter. </p><p>•ꢀ Requires a <strong>source of energy </strong>to drive </p><p>reactions: either light or chemical. </p><p>Metabolic Diversity:<sup style="top: -0.5158em;">Metabolism </sup>Source of Carbon </p><p>•ꢀ <strong>AUTOTROPHS</strong>: Need only carbon </p><p>dioxide (CO<sub style="top: 0.1959em;">2</sub>) as carbon source </p><p>•ꢀ <strong>HETEROTROPHS</strong>: Need at least one </p><p>organic nutrient as carbon source (e.g. glucose; petroleum) </p><p>•ꢀ Both of these present in domain Eucarya as well. </p><p>Metabolic Diversity:<sup style="top: -0.5158em;">Metabolism </sup>Source of Energy </p><p>•ꢀ <strong>PHOTOTROPHS</strong>: Need only sunlight as </p><p>energy source </p><p>•ꢀ <strong>CHEMOTROPHS</strong>: Derive energy from </p><p>oxidation of organic molecules. <br>•ꢀ Both of these present in domain Eucarya as well. </p><p>10 <br>2/4/15 </p><p>Metabolism </p><p>Metabolic Diversity: Combined </p><p>Energy Source: </p><ul style="display: flex;"><li style="flex:1">Sun </li><li style="flex:1">Environment </li></ul><p></p><p></p><ul style="display: flex;"><li style="flex:1"><strong>Photoautotroph </strong></li><li style="flex:1"><strong>Chemoautotroph </strong></li></ul><p></p><p>CO<sub style="top: 0.1709em;">2 </sub>Organic molecules </p><p><strong>Photoheterotroph Chemoheterotroph </strong></p><p>Which of these are present in multicellular Eucarya? </p><p>Metabolism </p><p>Photoautotrophs </p><p>•ꢀ Use sun for energy, CO<sub style="top: 0.1708em;">2 </sub>for carbon. <br>•ꢀ Photosynthetic bacteria (e.g. cyanobacteria). <br>•ꢀ Present in many plants and singlecelled Eucarya </p><p>Metabolism </p><p>Chemoautotrophs </p><p>•ꢀ Oxidize inorganics <br>(H<sub style="top: 0.1465em;">2</sub>S, NH<sub style="top: 0.1465em;">3</sub>) for energy. <br>•ꢀ Need only CO<sub style="top: 0.1469em;">2 </sub>as carbon source. <br>•ꢀ Unique to Bacteria and Archaea. </p><p>•ꢀ E.g. <em>Methanococcus jannaschii </em>lives on </p><p>hydrothermal vents at 2600m below sea level. <br>•ꢀ Reduces H<sub style="top: 0.1475em;">2 </sub>+ CO<sub style="top: 0.1475em;">2 </sub>to CH<sub style="top: 0.1465em;">4 </sub>+ 2H<sub style="top: 0.1465em;">2</sub>O. </p><p>11 <br>2/4/15 </p><p>Metabolism Metabolism Metabolism </p><p>Photoheterotrophs </p><p>•ꢀ Get enery from light but must obtain carbon in organic form (NOT CO<sub style="top: 0.1707em;">2</sub>). <br>•ꢀ Unique to Bacteria and Archaea. </p><p>•ꢀ E.g. <em>Halobacterium salinarium</em>. </p><p>Chemoheterotrophs </p><p>•ꢀ Consume organic </p><p>molecules for <strong>both </strong></p><p>energy and carbon. <br>•ꢀ Common among prokaryotes: </p><p>–ꢀ <strong>saprobes </strong></p><p>(decomposers) </p><p>–ꢀ <strong>parasites </strong>(rely on </p><p>living hosts) </p><p>•ꢀ Also widespread in Protista, Animalia, Plantae. </p><p>Nitrogen metabolism </p><p>•ꢀ <strong>Nitrogen fixation</strong>: </p><p>•ꢀ The only* mechanism that makes atmospheric Nitrogen available to other organisms. <br>•ꢀ Convert N<sub style="top: 0.1469em;">2 </sub>into ammonia <br>(NH<sub style="top: 0.1469em;">3</sub>) which is quickly protonated into ammonium (NH<sub style="top: 0.1467em;">4</sub><sup style="top: -0.176em;">+</sup>). <br>•ꢀ <em>Essential </em>for multicellular life! </p><p>12 <br>2/4/15 </p><p>Oxygen Relationships </p><p></p><ul style="display: flex;"><li style="flex:1">•ꢀ Aerobic vs. Anaerobic </li><li style="flex:1">•ꢀ Cellular respiration: </li></ul><p></p><p>–ꢀ Carbohydrates + O<sub style="top: 0.11em;">2 </sub>→CO<sub style="top: 0.11em;">2 </sub><br>+ H<sub style="top: 0.1101em;">2</sub>O + energy </p><p>•ꢀ Obligate aerobes: use O<sub style="top: 0.1222em;">2 </sub>for cellular respiration. <br>•ꢀ Fermentation: <br>•ꢀ Facultative anaerobes: use </p><p>–ꢀ Carbohydrates →CO<sub style="top: 0.11em;">2 </sub>ethanol + energy <br>+</p><p>O<sub style="top: 0.1222em;">2 </sub>if it is present by carry out anaerobic respiration or fermentation in anaerobic environment. <br>•ꢀ Obligate anaerobes<strong>: </strong>poisoned by O<sub style="top: 0.1222em;">2</sub>; use anaerobic respiration or fermentation. <br>•ꢀ Anaerobic respiration: </p><p>–ꢀ Carbohydrates + [X] → bicarbonate + [X<sup style="top: -0.1319em;">-</sup>] + energy <br>–ꢀ Where [X] is a substance other than O<sub style="top: 0.11em;">2 </sub>that accepts electrons such as nitrates or sulfates </p><p>Oxygen Relationships </p><p>•ꢀ Early life (during the Archaean) was primarily anaerobic. <br>•ꢀ Evolution of photosynthesis in Cyanobacteria changed all this. </p><p>Taxonomy of Prokaryotes </p><p>•ꢀ Archaea or Archaebacteria </p><p>–ꢀ Methanogens –ꢀ Halophiles –ꢀ Thermophiles </p><p>•ꢀ Bacteria or Eubacteria </p><p>–ꢀ Protobacteria –ꢀ Chlamyidias –ꢀ Spirochetes –ꢀ Cyanobacteria –ꢀ Gram-positive bacteria </p><p>13 <br>2/4/15 </p><p>Archaea or Archaebacteria </p><p>•ꢀ Live in extreme environments (extremophiles): sulfur hot springs, deep sea vents, high salt environments. <br>•ꢀ Lack peptidoglycan, unique plasma membrane of liquids </p><p>•ꢀ Likely <strong>sister group </strong>of </p><p>Eukaryotes </p><p>Archaea or Archaebacteria </p><p>•ꢀ <em>Methanogens </em></p><p>–ꢀ Use H<sub style="top: 0.1467em;">2 </sub>to reduce CO<sub style="top: 0.1469em;">2 </sub>to methane (CH<sub style="top: 0.1465em;">4</sub>). <br>–ꢀ Chemoautotrophs –ꢀ Anaerobic –ꢀ In swamps, marshes, deep sea vents, important decomposers. </p><p>Archaea or Archaebacteria </p><p>•ꢀ <em>Halophiles </em></p><p>–ꢀ Saline environments. –ꢀ Salinity several times higher than sea water. <br>–ꢀ Photoheterotrophs </p><p>14 <br>2/4/15 </p><p>Archaea or Archaebacteria </p><p>•ꢀ <em>Thermophiles </em></p><p>–ꢀ 60º-80ºCpH 2-4 optimal <br>–ꢀ Chemoautotrophs –ꢀ Oxidize HS </p><p>Bacteria or Eubacteria </p><p>•ꢀ Grouped by molecular systematics. </p><p>Bacteria or Eubacteria </p><p>Proteobacteria </p><p>•ꢀ VERY diverse, grouped into five taxa based on DNA sequence data. <br>•ꢀ Includes most types of metabolism that we’ve discussed. <br>•ꢀ Includes most of the types of symbioses we’ve discussed <br>•ꢀ Review the summary in Figure 27.16. </p><p>15 <br>2/4/15 </p><p>Bacteria or Eubacteria </p><p>Gram positive Bacteria: </p><p>•ꢀ Simple peptidoglycan cell wall. •ꢀ Rival Proteobacteria in diversity. <br>•ꢀ Most are free-living decomposers. <br>•ꢀ Some pathogenic (e.g. strains </p><p>of <em>Staphylococcus</em>, <em>Streptococcus</em>, <em>Bacillus anthracis</em>, <em>Clostridium botulinum</em>). </p><p>•ꢀ Include the mycoplasms--the only bacteria that lack cell walls </p><p>Bacteria or Eubacteria </p><p>Cyanobacteria: </p><p>•ꢀ Photoautotrophs •ꢀ Only prokaryotes with plant-like, O<sub style="top: 0.1588em;">2</sub>-generating photosynthesis. <br>•ꢀ Present in freshwater and marine environments. <br>•ꢀ Often colonial--first steps toward multicellularity? </p><p>Bacteria or Eubacteria </p><p>Spirochetes: </p><p>•ꢀ Helical •ꢀ Recall motility: move by means of rotating, internal, flagellum-like filaments. <br>•ꢀ Free-living and parasitic. <br>•ꢀ Chemoheterotrophs <br>(like us). </p><p>16 <br>2/4/15 </p><p>Bacteria or Eubacteria </p><p>Chlamydias: </p><p>•ꢀ ALL are parasites of animals. <br>•ꢀ Intercellular. •ꢀ Lack peptidoglycan in the cell wall (are they gram-positive or gram-negative?). <br>•ꢀ Most common form of STD in USA (urethritis). </p><p>Prokaryotes: Summary </p><p>•ꢀ You should now have a good sense of prokaryote biology and diversity. <br>•ꢀ Including roles in metabolism, symbioses, global energy cycles. <br>•ꢀ Important distinguishing characteristics of cell wall, motility, genome, replication. <br>•ꢀ General aspects of their systematics. </p><p>17 </p>
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