Bio Microbiology - Spring 2013 Study Guide 14.

Transcription

1 Bio Microbiology - Spring 2013 Study Guide 14

2 Working Backwards to the Age of the Earth Radioactive decay is consistent with an age of 4.5 Billion Years

3 STRATIGRAPHY

4 The earliest stromatolite of confirmed microbial origin dates to 2,724 million years ago. Modern stromatolites in Shark Bay, Western Australia.

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6 Apparatus for the Miller-Urey Experiment

7 Progression to a Protocell

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9 "Metabolism" of a Coacervate The properties of artificial coacervates are similar to some of the properties of living cells. They are held intact by a non-lipid membrane-like coating. Chemical reactions take place in the interior in the presence of enzymes.

10 Pyrite - FeS ORIGIN OF LIFE: Life as We Don't Know It Wächtershäuser Science 25 August 2000: 1307 Pyrite and the origin of life K. R. POPPER Nature 344, 387 (29 March 1990); doi: /344387a0

11 One reason why it is suggested that the initial formation of biological-like polymers must have taken place on the surfaces of minerals was: Minerals provide a dry surface for the dehydration reactions needed to produce biological polymers. GOLDEN PYRITE SUN ON 8.5" SLATE MATRIX

12 PYRITE World

13 Optical Activity is an Issue

14 Misconception: Evolution is a theory about the origin of life.

15 Origin of Microbial Life and Photosynthesis

16 The Evolution of Metabolism in the Proteobacteria: One Hypothesis The common ancestor of all proteobacteria was probably a photoautotroph. As they encountered new environments, Groups 1 and 2 lost the ability to photosynthesize; in the other three groups, some evolutionary lines became chemoautotrophs or chemoheterotrophs.

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18 Self-Splicing RNA

19 Introns in the 16S rrna genes of the large sulfur bacteria. (A) Four introns were inserted in the positions 795, 1078, 1396, and 1495 (according to E. coli numbering) in the gene for the small ( S ) ribosomal subunit (16S rdna). (B) Multifurcation tree based on nearly full-length 16S rrna gene sequences of members of the family Beggiatoaceae showing the occurrence of introns in the different genera and species. To date introns have been located in 16S rrna genes of the genera Thiomargarita, Candidatus Marithioploca, Candidatus Thiopilula, and Candidatus Thiophysa.

20 A Ribozyme from a Protist The folded three-dimensional structure of this catalytic RNA, or ribozyme, enables it to catalyze chemical reactions during protein synthesis. RNA catalysis may have preceded enzyme catalysis in the evolution of life.

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23 16S rrna molecules make great chronometers for determining the patterns of microbial evolution because: a. Most bacteria contain rrna and it carries out the same function in each of them. b. Conserved regions are useful for aligning sequences determined from different organisms. c. They are big enough (1,500 nt) to provide useful information. d. They can be relatively easily isolated and sequenced using direct methods and/or PCR.

24 A Globin Gene Tree The globin family gene tree suggests that myoglobin diverged from modern hemoglobin precursors about 500 mya, at about the time of the origin of vertebrates.

25 Cytochrome c Molecules Evolved at a Constant Rate Rates of substitution in cytochrome c are constant enough that this molecule can be used as a molecular clock.

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30 Lynn Margulis

31 History of Ideas Concerning Endosymbiosis 1883 ~ AFW Schimper noted that the plastids of plant cells resembled free-living Cyanobacteria ~ Mereschkowsky proposed a reticulated tree of endosymbiosis for the origin of algal plastids. 1920s ~ Ivan Wallin suggested a bacterial origin for mitochondria ~ Stocking and Gifford discovered DNA in the plastids of Spirogyra, a green algae. 1960s ~ Lynn Margulis argued the case for endosymbiotic origins of mitochondria and plastids ~ Margulis published her argument for the endosymbiotic origin of eukaryotes in The Origin of Eukaryotic Cells. 1977~ Carl Woese declared the case for prokaryotic endosymbiosis clear cut and proven. Other biologists subsequently declared the endosymbiotic theory demonstrated beyond a reasonable doubt ~ In Symbiosis in Cell Evolution, Margulis argued that eukaryotic cells originated as communities of interacting entities. She extended the argument to including endosymbiotic incorporation of spirochaetes that developed into eukaryotic undulopodia -- flagella and cilia. (This proposal has not gained wide acceptance because flagella lack DNA and do not show ultrastructural similarities to prokaryotes.)

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34 Parsimony Analysis A method used to create phylogenies of organisms based on the assumption that the evolution of characters occurs by the simplest (most parsimonious) path.

35 Three possible unrooted trees are shown. The top tree assumes 9 changes in character state occurred (each change is represented by a mark), the middle tree assumes 10 changes, and the bottom tree assumes 11. Because the top tree assumes the fewest changes, it is the most parsimonious tree.

36 The End