Carl Woese's distinguished career was dominated by his idea that divisions between different kinds of living organisms could be better defined by their small subunit ribosomal RNA(smaller bottom piece here) sequences than by their morphology, biochemistry, outer membrane, or even necessarily the most basic of divisions like multicellularity or the presence of cellular organelles. Indeed, seeing life through this much clearer lens, he was able to show that the microbes known as Archaea are at least as different from Bacteria as they are from Eukaryotes like plants and animals, a finding he presented here to much controversy and derision:“It’s clear to me that if you wiped all multicellular life-forms off the face of the earth, microbial life might shift a tiny bit, if microbial life were to disappear, that would be it — instant death for the planet.”-WoeseWoese, Carl R.; George E. Fox (1977). "Phylogenetic structure of the prokaryotic domain: the primary kingdoms.(PDF)". Proceedings of the National Academy of Sciences of the United States of America 74 (11): 5088–5090Fought for eloquently here:
A phylogenetic analysis based upon ribosomal RNA sequence characterization reveals that living systems represent one of three aboriginal lines of descent: (i) the eubacteria, comprising all typical bacteria; (ii) the archaebacteria, containing methanogenic bacteria; and (iii) the eurkaryotes, now represented in the cytoplasmic component of eukaryotic cells.Woese, Carl R. (1987-06-01). "Bacterial evolution.(PDF)". Microbiological Reviews 51 (2): 221–271And presented again thirteen years later, this time as core scientific dogma:
A revolution is occurring in biology: perhaps it is better characterized as a revolution within a revolution. I am, of course, referring to the impact that the increasingly rapid capacity to sequence nucleic acids is having on a science that has already been radically transformed by molecular approaches and concepts. While the impact is currently greatest in genetics and applied areas such as medicine and biotechnology, its most profound and lasting effect will be on our perception of evolution and its relationship to the rest of biology. The cell is basically an historical document, and gaining the capacity to read it (by the sequencing of genes) cannot but drastically alter the way we look at all of biology. No discipline within biology will be more changed by this revolution than microbiology, for until the advent of molecular sequencing, bacterial evolution was not a subject that could be approached experimentally. With any novel scientific departure it is important to understand the historical setting in which it arises-the paradigm it will change. Old prejudices tend to inhibit, distort, or otherwise shape new ideas, and historical analysis helps to eliminate much of the negative impact of the status quo. Stch analysis is particularly importaht in the present instance since microbiologists do not deal with evolutionary considerations as a matter of course and so tend not to appreciate them. Therefore, I begin this discussion with a brief look at how the relationship between microbiology and evolution (i.e., the lack thereof) developed.Woese, C R; O Kandler, M L Wheelis (1990). "Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya.(PDF)". Proceedings of the National Academy of Sciences of the United States of America 87 (12): 4576–4579.
Molecular structures and sequences are generally more revealing of evolutionary relationships than are classical phenotypes (particularly so among microorganisms). Consequently, the basis for the definition of taxa has progressively shifted from the organismal to the cellular to the molecular level. Molecular comparisons show that life on this planet divides into three primary groupings, commonly known as the eubacteria, the archaebacteria, and the eukaryotes. The three are very dissimilar, the differences that separate them being of a more profound nature than the differences that separate typical kingdoms, such as animals and plants. Unfortunately, neither of the conventionally accepted views of the natural relationships among living systems--i.e., the five-kingdom taxonomy or the eukaryote-prokaryote dichotomy--reflects this primary tripartite division of the living world. To remedy this situation we propose that a formal system of organisms be established in which above the level of kingdom there exists a new taxon called a "domain." Life on this planet would then be seen as comprising three domains, the Bacteria, the Archaea, and the Eucarya, each containing two or more kingdoms. (The Eucarya, for example, contain Animalia, Plantae, Fungi, and a number of others yet to be defined). Although taxonomic structure within the Bacteria and Eucarya is not treated herein, Archaea is formally subdivided into the two kingdoms Euryarchaeota (encompassing the methanogens and their phenotypically diverse relatives) and Crenarchaeota (comprising the relatively tight clustering of extremely thermophilic archaebacteria, whose general phenotype appears to resemble most the ancestral phenotype of the Archaea.
Later in life he became something of an elder statesman of evolutionary microbiology publishing the occasional review:Today, whenever a student of biology opens their textbook what they see first is a blown up image of the tripartite tree of life – a small tribute to a man and a discovery that changed our view of nature forever."Woese, Carl R.; Nigel Goldenfeld (2009). "How the Microbial World Saved Evolution from the Scylla of Molecular Biology and the Charybdis of the Modern Synthesis". Microbiology and Molecular Biology Reviews 73 (1): 14–21.
In this commentary, we provide a personal overview of the conceptual history of microbiology and molecular biology over the course of the last hundred years, emphasizing the relationship of these fields to the problem of evolution. We argue that despite their apparent success, all three reached an impasse that arose from the influence of dogmatic or overly narrow perspectives. Finally, we describe how recent developments in microbiology are realizing Beijerinck's vision of a field that is fully integrated with molecular biology, microbial ecology, thereby challenging and extending current thinking in evolution.
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