Jonathan Eisen (@phylogenomics on Twitter) has a new post on his The Tree of Life blog that looks at why the paper "Phylogenetic structure of the prokaryotic domain: The primary kingdoms" by Carl Woese and George Fox may be the most important paper (see http://www.pnas.org/content/74/11/5088.full.pdf+html?sid=867a6a9e-fd2f-4122-a1db-9ac96a9798b7) in the history of microbiology.
"In this paper they lay out the evidence for the existence of at least three main branches in the Tree of Life. Interestingly, for the phylogenetically minded people out there, they do not show an evolutionary tree in the paper. What they show is what is known as a similarity matrix (the inverse in essence of the distance matrices many people may be used to seeing) where a score is given for the similarity between organisms in the fingerprints of their 16S/18S rRNAs)."
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