PhylogenticTrees

PhylogenticTrees - 1060 Dispatch Phylogenetic trees:...

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1060 Dispatch Phylogenetic trees: Whither microbiology? Carl R. Woese The direct cloning and sequencing of genes from uncultured microorganisms in a hot spring suggests that the diversity of life on Earth may be far in excess of that estimated from culturable species. Address: Department of Microbiology, University of Illinois, Urbana, Illinois 61801, USA. Current Biology 1996, Vol 6 No 9:1060–1063 © Current Biology Ltd ISSN 0960-9822 Mendel and Darwin represent two different ways of looking at biology, contrasting in how they organize and interpret biological information, and in their visions of biology’s future and relationship to society. The Mendelian perspective — symbolized by the double- stranded structure of DNA — is reductionist, and focuses on structure and function. The Darwinian perspective — symbolized by the universal phylogenetic tree — is holis- tic, and focuses on evolutionary histories, organismal rela- tionships and biodiversity. Yet it would be wrong to consider these two perspectives merely as alternatives, as contrary or mutually exclusive. Every organism, cell or macromolecule is both an entity with structure and func- tion and an embodiment of its own evolutionary history. The complete biological picture thus grows out of a dialec- tic synthesis of the two perspectives, not from one or the other alone. Nothing illustrates the need for this synthesis better than microbiology. Until quite recently the field of microbiology necessarily developed only within the Mendelian framework. Over the past two decades, however, the Darwinian side of microbiology has finally emerged, with profound conse- quences. This is well illustrated by the results of an ongoing survey of the microbial diversity in one Yellow- stone National Park hot spring, the Obsidian Pool, by the direct cloning of gene sequences from environmental samples [1,2]. This study is a prime example of the power and scope of a microbiology that reflects a synthesis of the Mendelian and Darwinian paradigms. To appreciate fully the change that the field is undergo- ing, one has to see the situation from an historical perspec- tive. During the middle half of this century, microbiology prospered within a strictly Mendelian framework. Indeed, most of the great discoveries of the day in biochemistry, genetics and molecular biology were made in microbial systems. But the field’s Darwinian side lay completely undeveloped: microbial phylogenies simply cannot be determined upon the basis of phylogenetically unreliable characteristics such as bacterial morphologies and gross physiological properties, the only phylogenetic markers available at the time [3]. This led to a situation in which a lot of molecular/genetic details were known about a few bacteria, but there was no real biological understanding of bacteria as a whole — no real appreciation for the extent of microbial diversity and no comprehension of microbial rela- tionships. In the words of two of the great microbiologists of
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PhylogenticTrees - 1060 Dispatch Phylogenetic trees:...

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