Unit 1 - The Origins of Life Louis Pasteur December 27, 1822 – September 28, 1895

Pasteur’s swan neck flask

Pasteur’s sour wine

Radiometric dating of rocks (amîtsoq gneisses) from The Earth Is Old! Radiometric dating of rocks (amîtsoq gneisses) from Western Greenland Similar results from Australia, Wisconsin, Africa and Russia

Cyanobacterial microfossils

Extant stromatolites

Fossilized stromatolites

-Woese, Micro. Rev., 1987 The dilemma faced by microbiologist is that many bacteria look the same. It’s fairly to distinguish between the various plants and animals in a setting like this. But the two microbial species in these electron micrographs are all but indistinguishable. In 1977 a fella by the name of Carl Woese at the Univerity of Illinois changed all that. By comparing the DNA of many different organisms he convincingly showed the biological world, rather than 5 kingdoms, was more appropriately divided into three domains of living things: the Bacteria, the Archaea and the Eukarya. (You are here - point to humans). This is a phylogenetic tree. A tree of the similarity between the DNA of one organism and another. The shorter the distance between two organisms the more similar the DNA and by implication the more closely related they are. Based on Dna evidence these two organisms are vastly different. More divergentt than plants are from animals. One thing that you will note is that this tree does away with the hierarchy of the 5-kingdom scheme. The tip of each of these branches represents a living organism but it does not imply that one organism is more advanced than another - only genetically different. We’ll come back to this point in a couple of minutes.

Prokaryotes Eukaryotes

Archaea Chlamydia Low G+C gram positive Actinobacteria Cytophagales Planctomycetes Chlamydia Verrucomicrobia OP3 Acidobacterium Termite group I Nitrospira Synergistes OP10 OS-K Flexistipes Low G+C gram positive OP8 WS1 Cyanobacteria Actinobacteria Green non-sulfur Fibrobacter OP5 Marine group A OP9 Green sulfur Dictyoglomus Cytophagales Coprothermobacter Thermus/Deinococcus Thermotogales Thermodesulfobacterium Spirochetes TM6 Aquificales W88 TM7 0.10 Fusobacteria Proteobacteria OP11 Archaea J. Bacteriol. 1998; 180:4765-4774