Woese, Carl

Finally, paradigms frequently have the look of a sensible refuge in a chaotic sea of competing ideas. Monophyly is portrayed in precisely this way even if several alternative refuges are lurking on the horizon. For example, Carl Woese s alternative, which he calls the genetic annealing model (Woese,... 

A further (mathematical) model for the evolution of the genetic code was devised by Carl Woese and co-workers. This dynamic theory provides information on the evolvability and universality of the genetic code. One conceptual difficulty was due to the fact that it had been overlooked that the genetic code was highly communal... 

The origin of hving organisms on Earth has been summed up by Carl Woese, one of the leaders of scientific study and thought in this field, in the following way ... 

The unveiling of the structural and functional complexity of RNA led Carl Woese, Francis Crick, and Leslie Orgel to propose in the 1960s that this macromolecule might serve as both information carrier and catalyst. The discoveiy of catalytic RNAs took this proposal from... 

Carl Woese Francis Crick Leslie Orgel... 

At first, trees depicting a symbiotic origin of mitochondria and chloroplasts were sketchy, and were cobbled together from partial sequences of diverse molecules, 5S RNA, ferredoxin, cytochrome c, based on very few organisms (Schwartz and Dayhoff 1978). They were easily criticized (Demoulin 1979). The decisive evidence came from systematic investigations of bacterial phylogeny based on comparisons of the small subunit ribosomal RNA (SSU rRNA) pioneered by the group led by Carl Woese at the University of Illinois. 

All living cells contain ribosomal RNAs, and it seems that these nucleic acids have changed very little in the course of evolution because their structures are similar in all organisms. Despite this enormous molecular uniformity, however, all species are slightly different in their ribosomal RNAs, and in 1977 Carl Woese showed that these little differences give us precious information on the very first stages of cellular evolution. 

Figure 6.1 The species correlation coefficients obtained by Carl Woese from...

The lack of a murein cell-wall sacculus and the discovery of different cell-envelope polymers and structures in some physiologically unusual prokaryotes, was one of the first biochemical and cytological evidences in favour of Carl Woese s archaebacteria concept [46,149,150]. Since then, increasingly more unique cell-envelope polymers and new types of biosynthetic pathways have become known. These findings corroborate the proposal that the archaea represent a third lineage of organisms [150] in addition to bacteria and eucarya, and that the common ancestor or ancestral population of the archaea did not evolve any cell-wall polymer before it radiated into the various sublineages known today [46,151]. 

On the basis of sequence comparison of 16S rRNA sequences Carl Woese and coworkers had divided the prokaryotic domain into two urkingdoms of life, the eubacteria and the archaebacteria, each a coherent entity distinct from the other as well as from the third urkingdom, the eukaryotes [1,2]. Recently Woese et al. [3] have proposed to call the highest taxon level a domain instead of an Urkingdom, and to rename the three domains of life Bacteria, Archaea and Eucarya in order to emphasize their distinction as equally separate major entities. 

The archaea were only recognized as a distinct group of organisms in 1977 when Carl Woese analyzed specific nucleic acid molecules. Comparison of the molecular properties of archeans to those of bacteria and eukaryotes has revealed that archeans are in many ways closer to the eukaryotes than to the outwardly similar bacteria. For example, the archean system for synthesizing protein is more like that of eukaryotes. 

For many years the phylogenetic tree was believed to possess two main branches the prokaryotes and the eukaryotes. Largely because of Carl Woese s pioneering work with rRNA sequences, it has become apparent that the relationships among currently existing life forms are more complex than the two-domain model implies. Small ribosomal subunit RNA molecules are especially useful for probing phylogenetic relationships because ... 

Figure 10 A rooted universal tree of life, showing the three domains of life. The tree is based on sequence comparisons of ribosomal RNA, analysed by Carl Woese and his colleagues. The order and length of branches are proportional to the sequence similarities within and between the domains and the kingdoms of life — in other words, they are directly proportional to the genetic similarities between species. It is humbling to note that the animals, plants and fungi account for just a small comer of the Eucarya domain, and that there is less variation in ribosomal RNA sequences within the entire animal kingdom than there is between different groups of methanogen bacteria.

Catalysts played an important role in the emergence of life on Earth nearly 4 billion years ago. Catalysis by mineral surfaces and small molecules enabled the emergence of a proto-metabolic network that, in turn, enabled the emergence of the RNA world. The first macromolecular catalysts may have been ribozymes, an idea first proposed by Carl Woese that gained credence with the discovery of catalytic RNAs by Cech and Altman. Subsequently, ribozymes generated by in vitro evolution methods have been shown to catalyze a wide range of reactions involved in metabolism, including amino acid activation formation of coenzyme A (CoA), nicotinamide adenine dinucleotide (NAD), and flavin adenine dinucleotide (FAD)... 

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