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Lecture 3 - Origin of life and Microbes, microbial evolution, metabolism and diversity
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- 1evidence for microbial life can be found in rocks that are ______ old3.5 billion years old
- 2Earth formed ___4.5 billions years ago
- 3oceans formed4.3 billions years ago
- 4Stromatolitesfossilized microbial mats consisting of layers of filamentous prokaryotes and trapped sediment
(fossilized stromatolite vs. modern stromatolite) - 5Alexander Oparin & JBS Haldane1920s, were precursors of modern ideas of origin of life
- 6planetary science-clues for organic synthesis
environment conditions (uv radiation, electric discharges, c present in inorganic, highly reducing environments) - 7Primordial soup-hot and diluted soup proteins and other organic compounds form colloidal systems: coacervates. one theory was that origin of life arose out of this soup- surface conditions were hostile so this is not possible
- 8Harold Urey 1950's-primitive earth had reducing atmosphere, molecules saturated with hydrogen atoms that can reduce other molecules
-planets in solar system have this kind of atmosphere. their atmosphere contained methane, ammonia, hydrogen and water - 9stanley millerfirst experiments designed to clarify chemical reactions in the primitive earth
- 10what did miller's experiment find?conclusion: the organic building blocks of life are generated in the probable atmosphere of early Earth. by reducing atmosphere with gases in prebiotic earth
- 11what is still revealing secrets of early solar system?meteorite that fell in 1969
- 12microfossils from apex chert, australia are how old?1 billion years old.
- 13surface origin hypothesis-the first membrane-enclosed, self replicating cells arose out of primordial soup rich in organic and inorganic compounds in ponds on earth's surface.
-dramatic temp fluctuations, uv radiation, mixing of metor, dust cloud, storms argue against this hypothesis - 14subsurface origin hypothesislife originated in hydrothermal vents deep in the ocean
-steady and abundant supply of required molecules and energy may have been available at these sites
-protected from UV and from temperature fluctuations - 15Marine hydrothermal ventshas been proposed that amino-acid synthesis could have occurred deep in the Earth's crust and that these amino-acids were subsequently shot up along with hydrothermal fluids into cooler waters (and the presence of clay minerals would have fostered the formation of peptides etc
- 16Montmorillonite-supply of reduced compounds H2 and H2S for energy. Montmorillonite clays catalyzer for the formation of key organic molecules nucleotides, lipids and proteins the bricks of life.
- 17RNA world-The RNA world hypothesis proposes that self-replicating ribonucleic acid (RNA) molecules were precursors to all current life on Earth. It is generally accepted that current life on Earth descends from an RNA world, although RNA-based life may not have been the first life to exist.
- 18RNA has the ability to act as both _____ and ______1) genes
2) enzymes - 19RNA can be transcribed into ____ in reverse of the normal process of ______1) dna
2) transcription
(reasons why rna world would be considered) - 20early life may be based on RNA to:store and replicate genetic information & catalyze chemical reactions
- 21What are the RNA properties in support of RNA-based protocell1) RNA like DNA can store and genetic information
2) RNA like proteins can catalyze chemical reactions
3) RNA can direct RNA synthesis, in the lab (rna polymerase) - 22significance of replicase-scientists hypothesize that a ribozyme that was capable of making copies of other RNAs called replicase evolved early in life's history. (true replicase has not been found)
- 23montmorillonite & rna-montmorillonite-catalyzed formation of RNA oligomers; the possible role of catalysis in the origins of life.
-montm..promote RNA synthesis at a faster rate than its degradtion - 24Lipid membrane-fatty acids can form inside thermal vents and geysers
-montmorillonite can induce de formation of fatty acid vesicles that can growth and divided
(ph - 25Fatty acids vs. phospholipids1) phospholipids compose modern cell membranes
2) fatty acids proposed for protocells (small carboxylate head group that is easily neutralized, allows fatty acids to rapidly flip across bilayer generating high permeability. fatty acids membranes are in equilibrium with micelles and single free fatty acids transfer in b/w these structures in second to minute time scale - 26red tagged rna molecule bound to _____ in a lipid vesiclemontmorillonte
- 27first organismProbiont/protocell (rna enclosed by lipid membrane)
- 28when does competition emerge?when protocells containing replicating genomes steal membrane from protocells containing inactive molecules
- 29eventually rna could have given rise to structurally similar double stranded ____Dna in cellular life form.
- 30LUCALast universal common ancestor (primordial to RNA to this)
- population of early prokaryotic hyperthermophilic (cell grown in deep sea hypoterhmal vent sulfur rich 150-300C) anaerobic cells form which cellular life may have diverged into ancestors of modern day Bacteria and Archae - 31what happens when o2 becomes freely available?protects sun from uv lights - mutation rates slow down (happens around 2.5-3.0 billion years ago)
- 32evolution of luca
- 33what kind of metabolism could LUCA have had?
- 34environment?-reducing atmosphere
-high temperature
-UV radiation - 35menu-of luca1) anaerobic
2) inorganic sources of carbon
3) reduced inorganic compoints
4) H2 - 36metabolisms in modern microorganismluca could be Chemolithotrophic autroph or chemolitoautroph (remember absence of O2)
- 37gram positives have ___ membrane1 mebrane
-gram negatives have more than one membrane - 38to obtain energy organisms ____ molecules or use lightOXIDIZE
- 39we are ______ that mainly oxidase organic compounds like glucose to obtain CO2 and H2O to C, reducing power and energyglucose -> glycolysis ->pyruvate ->acetylcoa-> TCA krebs cycle oxidation -> electrons go to etc (membrane of mitochondria)
- 40oxidative phosphorylation:harvest the energy from the proton motive force to make ATP
- 41glycolysisbreakdown of glucose to pyruvate (occurs in cytoplasm of prokaryotes and eykaryotes)
- 42tricarboxulic acid/krebs/citric acid cycle-widely distributed among microorganisms
-fuels the electron transport chain
-generates precursers for anabolic reactions
-in prokaryotes: CYTOPLASM
-in eukaryotes: MITOCHONDRIAL MATRIX - 43electron transport chain (aerobic resp)-series of electron carriers arranged in 4 complexes, operate together to transfer electrons from reduced NADH and FAD to a terminal electron acceptor
-Prokaryotes: Located in PLASMA membrane
eukaryotes: inner mitochondrial membrane - 44gram positive bacteria when1) no outer membrane
2) cell wall super thick (peptidoglycan) - 45redox tower-better electron donors (co2, glucose,methanol, nadh,fadh,pyruvate)...better at accepting (h20,02,fe, n03)
-the larger the jump, the larger the amount of energy released by the reaction - 46oxidation process-electrons reduce carriers of increasing positive redox potential to ultimately reduce O2 to produce h20
- 47what happens as electrons are transferred?energy is released and utilized for synthesis of ATP -> oxidative phosphotylation
1/2 O2 +2H + 2e => H2O - 48Substrate-level phosphorylation-uses the chemical energy from an exergonic reaction to produce ATP by phosphorylation of ADP (atp produced in glycolysis and krebs cycle. enzyme directly produces it)
- 49oxidative phosphorylation1) when electrons are transported through etc protons are extruded to the outside membrane
2) charge separation across the membrane generates the proton motive force
3) proton motive force generates ATP by oxidative phoshorylation - 50anaerobic respiration-carried out by bacteria and archaea
-exogenous terminal electron acceptor, different from O2 which are used for etc
**final electron acceptors as NO3, SO4, CO2, Fe, SeO4 - or organic acceptors
-yields LESS energy because e'o of electron acceptor is less positive than o2 ones
-glycolysis and TCA cycle may function the same during both aerobic and anaerobic respiration but fuelling electrons to different carriers - 51luca environment and menu-anaerobic and strong uv radiation
-reduced inorganic compounds
-feS, H2, H2S available in these sites as a source of energy and electrons
-source of carbon- co2 - 52luca's metabolismbased in: H2, source of energy and electrons donor
S: electron acceptor, reduced to produce H2S (waste-gassy smell)
CO2 is fixed (reduced) to produce organic compounds with e- and ATP coming from H2 oxidation - 53hyperthermophiles can live in65-110 C temperatures
-modern deep ocean thermal vents which present such conditions are populated by hyperthermophillic, H2 oxidizers, chemolithotrophic procaryotes - 54Pyrolobus fumarii can live at ____ in submarine hydrothermal vents Aquifex aeolicus grows near volcanoes or hot springs at temperatures up to _____ degrees113, 95 degrees
- 55modern chemolithotrophs-oxidation of H2
-H2-> 2H +2e
-requires hydrogenase
-H2 can donate to e- directly to ETC or first to reduce NAD+ that will subsequently donate etc - 56terminal acceptors may beO2, Fe, S, or CO
- 57if organic sources of carbon are available for energythey will switch from chemolithotrophic to chemoorganotrophic metabolism
- 58H2 based metabolism producesenergy atp for the fixation of CO2 to form cellular organic material. the accumulated organic material served as nutrients that allowed the appearance of different metabolism
- 59first cell..
- 60phototrophic organisms-convert light energy into chemical energy for growth. photosynthetic organisms are phototrophic but not the other way around.
red microbial...phototrophic - 61photosynthesisthe reduction (fixation) of CO2 into organisms using energy derived form light. Co2 reduction requires both atp and electrons. conseuquence - synthesis of carbohydrates and other molecular products to form biomass.
the electron source can be H2O, H2S, H2 or other reduced inorganic compounds - 62electron source of photosynthesis-H2O, H2S, H2
- 63oxygenic photosynthesis-eucaryotes and cyanobacteria
- 64anoxygenic photosynthesisall other bacteria, and archae
- 65stromatolites-fossilized microbial mats consisting of layers of filamentous prokaryotes and trapped sediment
-found in rocks 3.5 billions years old or younger - 66chloroflexusbeen proposed that modern cholorflexus may be a early form of phototroph that first evolved a photosynthetic reaction centre and cholorosomes
- 67anoxygenic photosynthesis1)carried out by phototrophic green bacteria, purple bacteria and heliobacteria
2) take place in cholorosomes attatched to inner membrane
3) mainly strict anaerobes
4) H2) is not used as an electron source => O2 is not produced
5) Pigment bacteriocholrophylls absorbs at a larger wavelength than cholorophylls
6) only one photosystem involved - 68chlorobigreen sulfur bacteria
-obligately anaerobic photoautotroph
electron source: H2S, elemental sulfur and H2
-carbon source: CO2
-some have gas vesicles to adjust depth of cell for adequate light and H2S - 69chlorosomes:-ellipsoidal vesicles attached to plasma membrane
- 70chlorosome-large antennae complex in the form of membranous vesicles that contain bacteriocholophyll molecules and accessory pigments
-most efficient light harvesting complexes found in nature
-transfer energy to bacteriocholophyll reaction centres located in the plasma membrane. (insect eye so can capture as much light as it can) - 71cyanobacteria (oxidative phosphorylation)before the rise of eukaryotes, 2.7 billion years ago. cyanbacterial lineages developed oxygenic photosynthesis
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