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January 20, 2012

PNAS Classic Article Covers 1977 Evolutionary Biology Paper Co-Authored by UH's George Fox
Perspective Piece Addresses Work of Fox and Carl Woese

PNAS

A 1977 paper co-authored by George Fox, now professor of biology and biochemistry at University of Houston, and his mentor at University of Illinois, Carl Woese, is the subject of the PNAS Classic Perspective article, “Phylogeny and beyond: Scientific, historical, and conceptual significance of the first tree of life.” The perspective piece, written by Norman R. Pace, Jan Sapp, and Nigel Goldenfeld, published online Jan. 17 in the Proceedings of the National Academy of Sciences Early Edition.

The authors provide a historical perspective of the 1977 article, “Phylogenetic structure of the prokaryotic domain: The primary kingdoms,” written by Woese and Fox, who was at that time a postdoctoral fellow working with Woese.

The perspective piece is summarized by the authors in their abstract:

“In 1977, Carl Woese and George Fox published a brief paper in PNAS that established, for the first time, that the overall phylogenetic structure of the living world is tripartite. We describe the way in which this monumental discovery was made, its context within the historical development of evolutionary thought, and how it has impacted our understanding of the emergence of life and the characterization of the evolutionary process in its most general form.”

Fox points out that the single most worrisome thing about the original proposal was the fact that it assigned the status of phylogenetic domain to just a single group of organisms, the methanogens, in effect, equating the importance of this single group to all other bacteria known at the time.

Fox states “for this reason, I examined the literature extensively and identified extreme halophiles, and two poorly characterized extremophiles, as additional candidate members of the proposed Archaea Domain. After I left Carl’s lab in 1977, it was gratifying to see that these additional organisms all subsequently proved to be Archaea.” There are now large numbers of organisms living in a large variety of ecological niches that are known to belong to the Archaea.

As quoted in a related PNAS article, co-author of the perspective piece, Norman Pace, a University of Colorado, Boulder, molecular biologist, said, “Without Woese’s 1977 report, today’s microbial sequencing efforts would not be meaningful. Woese put a framework of organization on microbial diversity.”

In their closing, the authors describe what they consider to be the 1977 paper’s legacy:

“Woese and Fox set out to determine the degrees of relatedness between all living organisms, using rRNA sequences as a marker of cellular evolution on slow time scales subsequent to the emergence of the modern lines of descent. They discovered that there are three domains of life, not two domains as had been previously believed. Their work also strongly constrained the nature of life for times shorter than about 1 billion years, indicating that before the emergence of a strong phylogenetic signal of vertical descent, early life had to evolve rapidly; we now suspect that its evolution was reticulate in nature. Modern versions of the techniques used by Woese and Fox are now routinely used to sample environments as varied as geothermal hot springs and gastrointestinal microbiomes, providing unprecedented insight into community structure and dynamics. The results challenged the foundations of classical evolutionary theory, requiring new modes of evolution to be considered, indicating the presence of an unexpectedly large microbial pangenome (“a field of genes” to use Woese’s favorite phrase), and forcing us to reconsider basic concepts such as the nature of species. Perhaps no other paper in evolutionary biology has left a richer legacy of accomplishments and promise for the future.”

Read the related PNAS Classic Profile, “Woese and Fox: Life, rearranged.”

- Kathy Major, College of Natural Sciences and Mathematics