Bio 230 - Microbiology - Spring 2013
Study Guide 14
http://www.swarthmore.edu/NatSci/cpurrin1/evolk12/slm/origindayimages/06soup.jpg
Working Backwards to the Age of the Earth
Radioactive decay is consistent with an age of 4.5 Billion Years
http://www.cbu.edu/~jholmes/N111/Part24/sld018.htm
STRATIGRAPHY
http://www.gobiernodecanarias.org/educacion/penelope/Strat3.gif
http://earthsci.org/fossils/palaeo/images/scale.gif
The earliest stromatolite
of confirmed microbial
origin dates to
2,724 million years ago.
Modern
stromatolites in
Shark Bay, Western
Australia.
http://www.resa.net/nasa/images/mars/stromatolite.jpg
Apparatus for the Miller-Urey Experiment
http://www.physics.hku.hk/~tboyce/sfseti/15origin.html
http://upload.wikimedia.org/wikipedia/commons/4/40/UreyMillerExperiment.jpeg
Progression to a Protocell
http://exobiology.nasa.gov/ssx/biomod/origin_of_life_slideshow/Molecules.Protocell.big.jpg
http://exobiology.nasa.gov/ssx/biomod/origin_of_life_slideshow/prebiotic_bio_path.big.jpg
"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.
http://www.mie.utoronto.ca/labs/lcdlab/biopic/fig/25.03.jpg
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:10.1038/344387a0
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
PYRITE World
http://www.wellesley.edu/Chemistry/chem227/origins/1307-1-med.gif
Optical Activity is an Issue
http://www.btools.com/images/fig1.gif
Misconception: “Evolution is a theory about the origin of life.”
http://evolution.berkeley.edu/evosite/misconceps/IAorigintheory.shtml
Origin of Microbial Life and Photosynthesis
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.
http://www.mie.utoronto.ca/labs/lcdlab/biopic/fig/26.12.jpg
http://commons.wikimedia.org/wiki/File:DNA_exons_introns.gif
Self-Splicing RNA
http://138.192.68.68/bio/Courses/biochem2/RNA/SelfSplicingRNA.html
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.”
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.
http://www.mie.utoronto.ca/labs/lcdlab/biopic/fig/25.04.jpg
http://www.ess.sunysb.edu/lattimer/AST248/tr31.gif
http://exobiology.nasa.gov/ssx/biomod/origin_of_life_slideshow/RNAWorldCritique.big.jpg
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.
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.
http://www.mie.utoronto.ca/labs/lcdlab/biopic/fig/24.07.jpg
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.
http://www.mie.utoronto.ca/labs/lcdlab/biopic/fig/24.06.jpg
http://epicofevolution.com/treeoflife.html
Lynn Margulis
http://www.snowballearth.org/images/Lynn_Margulis.jpg
History of Ideas Concerning Endosymbiosis
1883 ~ AFW Schimper noted that the plastids of plant cells resembled free-living
Cyanobacteria.
1905 ~ Mereschkowsky proposed a reticulated tree of endosymbiosis for the origin of
algal plastids.
1920s ~ Ivan Wallin suggested a bacterial origin for mitochondria.
1959 ~ 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.
1970 ~ 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.
1981 ~ 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.)
http://endosymbionts.blogspot.com/
http://www.ualr.edu/botany/algal_phylogeny.jpg
http://www.life.umd.edu/labs/Delwiche/pubs/endosymbiosis.gif
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.
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.
The End