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Unformatted text preview: today’s factoid • ﬁrst report of success in an AIDS vaccine trial • experimental vaccine was made by combining two vaccines that had previously been unsuccessful • world's largest AIDS vaccine trial in Bangkok Thailand; > 16,000 volunteers • risk of HIV infecJon cut by 31% – "New infecJons occurred in 51 of the 8,197 given vaccine and in 74 of the 8,198 who received dummy shots." • An actual vaccine for public use based on the one in this trial is sJll years oﬀ • see 'AIDS Vaccine Progress' posted in Biology in the News on Blackboard Metabolic diversity in Prokaryotes • Prokaryotes have had billions more years than eukaryotes to adapt and evolve • Much greater metabolic diversity than eukaryotes Most bacteria and archaea, all animals, fungi, and many pro7sts are which nutri7onal category? • Photoautotrophs (light = energy source, C02 = carbon source) – Cyanobacteria ‐ use chlorophyll a • Release O2 as byproduct • H20 = “electron donor” • Like eukaryoJc photosynthesis PhotosyntheJc bacteria – Others use bacteriochlorophyll • Photoheterotrophs (light = energy source, organic carbon = carbon source) – Purple nonsulfur bacteria • Do not release O2 • Some have H2S as electron donor and release Sulfur instead of O2 hcp:// microbewiki.kenyon.edu/ index.php/Rhodobacter chemolithotrophs • Also called chemoautotrophs • Use inorganic molecules as energy source, e.g. • In the deep see near hydrothermal vents – CommuniJes exist with no light – Inorganic molecules such as H2S come from the volcanic vents – NH3 or NO2‐(nitrite) ‐> NO3‐ (nitrate) – Or H2, H2S, Sulfur hcp://www.botos.com/marine/mono3.jpg Prokaryotes and Nitrogen • Denitriﬁers can release nitrogen (e.g. Bacillus, Pseudomonas) • Nitrogen ﬁxing bacteria Bacillus anthracis – Normally aerobic but in anaerobic condiJons: 2NO3‐+10e‐+12H+‐>N2+6H20 – Convert atmospheric N2 to ammonium, which is usable by other organisms N2+6H ‐> 2NH3 • Crucial for all other organisms • Nitrogen in proteins, nucleic acids, etc. • Soil, ocean hcp://www.kimicontrol.com/microorg/Bacillus%20anthracis.jpg • Nitriﬁers: convert ammonia or nitrite to nitrate hcp://telstar.ote.cmu.edu/environ/m3/s4/cycleNitro.shtml • Many prokaryotes cannot be cultured – Only about 5000 species described Prokaryote relaJonships – Must obtain DNA samples from nature • Has revealed the existence of many many more species • Molecules are now very important in classiﬁcaJon and phylogeneJcs of prokaryotes • rRNA genes ‐ present in all organisms • Problem: lateral gene transfer (also called “horizontal gene transfer”) RelaJonships of major Prokaryote groups Major Prokaryote groups Treponema pallidum, the syphilis pathogen • Spirochaetes • ram negaJve G • hemoheterotrophs c • ove using axial ﬁlaments (see prev. lect) m • ncludes parasites: syphilis pathogen, Lyme disease pathogen i (Borrelia) Major Prokaryote groups • Chlamydias • smallest bacteria (0.2‐1.5 µm dia.) • Gram negaJve cocci with complex life cycle • Obligate parasites (apparently cannot produce much ATP by themselves) • Various infecJon types in humans, incl. STD Obligate versus facultaJve • Obligate indicates an organism must do some thing – e.g. Chlamydias are obligate pathogens • FacultaJve means an organism can do one thing in one situaJon and another thing in a diﬀerent situaJon – e.g. many bacteria that grow as symbionts in animal guts can also grow in isolaJon in the laboratory • (symbiosis means a close, long‐term associaJon) Major Prokaryote groups • High GC Gram Posi7ve bacteria • Also called acJnobacteria (high GC content in DNA) • Many have ﬁlamentous growth • Tuberculosis (Mycobacterium tuberculosis) • Streptomyces species produce many anJbioJcs • note this is a diﬀerent genus from Streptococcus, which is in the low‐GC Gram PosiJve group Major Prokaryote groups Some cyanobacteria have cellular diﬀeren7a7on • Cyanobacteria • “blue green bacteria” • Photoautotrophs (use chlorophyll a) • Some can perform nitrogen ﬁxaJon • In ancient Earth, transformed the atmosphere by producing Oxygen • Many diﬀerent growth forms, free living or colonial Major Prokaryote groups • Low‐GC Gram posi7ve bacteria (not all are Gram posi7ve) • Some produce highly environmentally resistant endospores, to survive harsh environments • Can survive for 1000s of years, perhaps longer • This group includes Bacillus anthracis (anthrax), Clostridium botulinum (botulism), Staphylococcus, Streptococcus • Also includes Micoplasma, smallest known cellular organism (.2 µm) Major Prokaryote groups Agrobacterium tumifaciens is a Proteobacteria injects its DNA to transform plant cells a“gene7c engineer” of the bacterial world Crown gall disease caused by Agrobacterium • Proteobacteria • Largest bacterial group, also called “purple bacteria” • Huge diversity, especially in metabolism • Ancestor of the eukaryoJc mitochondria was a Proteobacteria • Includes some nitrogen‐ﬁxers, e.g. Rhizobium • Includes Escherichia coli • Diseases: Yersinia pes>s (bubonic plague), Vibrio cholerae (cholera), Salmonella typhimurium Major Prokaryote groups • ARCHAEA • Much less is known than in Bacteria • Known for extreme environments, but many in less extreme environments • Some have diﬀerent lipid membrane consJtuents than bacteria, eukaryotes Major Prokaryote groups • Crenarchaeota • Known for living in very hot and/or very acidic environments • Sulfolobus live in hot sulfur springs (70‐75˚C; pH 2‐3) Major Prokaryote groups Commercial sea salt evapora7ng ponds • Euryarchaeota • Some produce methane (methanogens); obligate anaerobes • In the guts of cacle and other mammals • Important source of atmospheric methane; greenhouse eﬀect • Also known for some extreme environments • e.g. extreme halophiles (very salty environments) • Reddish due to carotenoid pigments • Can withstand highly alkaloid environments (pH ~11) Prokaryotes provide vast and diverse beneﬁts to all life on Earth • • • • • DecomposiJon (along with Fungi) Nitrogen cycling Cyanobacteria in ancient Earth ‐> O2 Gut symbionts in animals; aid in digesJon and produce vital compounds, e.g. vitamin B12 Some are pathogenic (minority) – Human prokaroyJc pathogens are all Bacteria (not Archaea) – Some produce endotoxins (generally gram negaJve bacteria) ‐ released when cells lyse • Usually lipopolysaccharides • Cause various disease symptoms but are usually not fatal – e.g. Salmonella – Some produce exotoxins, highly toxic • Usually proteins • e.g. Clostridium (tetanus, botulism), Vibrio (cholera), Yersinia (plague), Bacillus anthracis (anthrax) Our prokaryote friends • Aid in manufacturing food products – Along with yeasts (fungi) Our prokaryote friends • Aid in waste water treatment Our prokaryote friends • GeneJc engineering and anJbioJcs – RestricJon endonucleases – Plasmids – Agrobacterium transformaJon of crop plants hcp://cndls.georgetown.edu/ applicaJons/posterTool/data/users/ cartoon044.jpg Origin and diversity of eukaryotes (Domain Eukarya) • How did they evolve? • Diversity, especially microbial eukaryotes – Many unicellular forms – Great reproducJve diversity – Many parasites, important diseases Eukarya Archaea • Impossible to memorize all of Ch. 27 – Concentrate on content of this lecture but go through the quesJons in the book / electronic resources Bacteria Two terms that are no longer in favor • ProJsts ‐ “eukaryotes that are neither land plants, animals, nor fungi” • Protozoans ‐ microbial eukaryotes that used to be classiﬁed as single‐celled “animals” • Modern phylogeneJc systemaJcs view indicates that these are non‐monophyle7c groups – you will ﬁnd out much more about monophyleJc groups later in the semester – a monophyleJc group contains a single ancestor and all of its descendants Eukaryotes • Loss of cell wall • • • • DigesJve vesicles More complex ﬂagella structure Nuclei Organelles – Chloroplasts • A few have lost mitochondria – Infolding of plasma membrane to increase surface area without increasing volume All of these innovaJons happened on this lineage > 1 billion years ago Eukarya – Almost all eukaryotes have mitochondria > 2 bya > 3 bya Archaea • Evolved mulJple Jmes • Primary, secondary (and even more complex) events Bacteria Loss of cell wall • Infolding of plasma membrane to increase surface area without increasing volume • Enables evoluJon of membrane‐bound structures inside the cell One possible sequence of eukaryote evoluJon Loss of cell wall infolding Internal membranes studded with ribosomes Cytoskeleton evolves (microﬁlaments, microtubules) DNA becomes acached to a membrane vesicle; precursor to the nucleus Flagellum evolves using cytoskeletal elements; propulsion is possible DigesJve vacuoles EndosymbioJc event gives rise to mitochondria EndosymbioJc event gives rise to chloroplasts Chloroplasts ‐ mulJple origins Only glaudophytes retained pepJdoglycan The key clue is the number of membranes surrounding the chloroplast 2 = primary 4 = secondary Some lineages have undergone two diﬀerent events; have two types of chloroplasts (terJary, quaternary may have also occurred) EndosymbioJc theory hcp://en.wikipedia.org/wiki/Image:Merezhkovsky_K_S.jpg • Mitochondria evolved from ancient bacteria • Chloroplasts evolved from ancient photosyntheJc bacteria or photosyntheJc eukaryotes • Originated by KonstanJn Mereschkowski in 1905 • Revived and invesJgated by Lynn Margulis in the 1960s‐1970s • Was once thought to be a strange idea • IniJal evidence was structural • DNA evidence sealed it hcp://en.wikipedia.org/wiki/Image:Lynn_Margulis.jpg hcp://porpax.bio.miami.edu/~cmallery/255/255hist/mcb1.15.cytoskeleton.jpg cytoskeleton • Important for: – MoJlity • Pseudopodia, cilia, ﬂagella hcp://ﬁg.cox.miami.edu/~cmallery/150/life/meiosis.pics.jpg – Chromosome movement during mitosis and meiosis Cytoskeleton components have been discovered in the thermophilic bacteria Thermotoga mari>ma • eukaryoJc cytoskeleton is made of acJn and tubulin protein monomers which polymerize into ﬁlaments • T. mari>ma has homologs of both proteins which are also capable of polymerizing into cytoskeletal structures – important for cell shape in this species • van den Ent, F., Amos, L.A., and Lowe, J. 2001 ProkaryoJc origin of the acJn cytoskeleton. Nature 413: 39‐44. • Thanks to Peter Balacky for ﬁnding this report bar is one micron (µm; 1 millionth of a meter) http:// www.genomenewsnetwork.or g/gnn_images/news_content/ 02_02/extremo_art/art2.jpg Bacterial vs. Eukarote ﬂagella • Bacterial ﬂagellum – Single “ﬁbril” composed of ﬂagellin (protein) – Hook and basal body drive moJon hcp://en.wikipedia.org/wiki/Image:Flagellum_base_diagram.svg • Eukaryote ﬂagellum – Independently evolved – Enclosed by plasma membrane – 9 pairs of microtubules surround 2 microtubules in the center hcp://ﬁg.cox.miami.edu/Faculty/Dana/ﬂagellum.jpg Eukaryote reproducJve diversity: conjuga7on • One group that does this: Paramecia Macronucleus ‐ used for running the cell Micronucleus ‐ used for meiosis, reproducJon • One group that does this: land plants and many other mulJcellular photosyntheJc eukaryotes MulJcellular eukaryote reproducJve diversity: alternaJon of generaJons between haploid and diploids gametophyte sporophyte Eukaryote reproducJve diversity: alternaJon of generaJons: isomorphic life cycle • One group that does this: many chlorophytes such as the sea lecuce Ulva lactuca Isogamy: male and female gametes are not diﬀerent (this is the case for U. lactuca but not all isomorphic species; some have Anisogamy) Eukaryote reproducJve diversity: alternaJon of generaJons: haplonJc life cycle • One group that does this: many chlorophytes such as Ulothrix hcp://boJt.botany.wisc.edu/images/130/ Chlorophyta/Ulothrix_130_.jpg Eukaryote reproducJve diversity: what are we? • DiplonJc life cycle hcp://en.wikipedia.org/wiki/Image:GameJc_meiosis.png ...
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This note was uploaded on 02/18/2010 for the course BIO 201 taught by Professor True during the Spring '08 term at SUNY Stony Brook.
- Spring '08