The site won't work, could post examples 4 and 9?
4.)
Adaptation to a Low Phosphate Chemostat Environment by a Clonal Line of Yeast
P.E. Hansche and J.C. Francis set up chemosats to allow evolution of a single clonal line of beer yeast in a phosphate limited (due to high pH) environment. (A chemostat is a device that allows the propagation of microorganisms in an extremely constant environment.) The yeast clones grew slowly for about the first 180 generations when there was an abrupt increase in population density. This was later shown to be due to better assimilation of the phosphate, presumably due to an improvement in the permease molecule. (Permease is an enzyme that controls what is allowed to come into the cell through the yeast's cell membrane.) After about 400 generations, a second improvement in cell growth rates occurred because of a mutation to the yeast's phosphatase (an enzyme that improves the cells ability to use phosphate). The phosphatase became more active overall, and its optimal pH (the pH where it is most active) was raised. Finally, a third mutant appeared after 800 generations that caused the yeast cells to clump. This raised the population density in the chemostat because individual cells were no longer being washed out of chemostat (which is one of the methods that the chemostat uses to maintain very uniform conditions) as quickly as they had prior to the mutation. (This is just speculation on my part, but I wonder if it wasn't under some similar conditions that multi-cellularity became favored over unicellularity - perhaps on a sea bed or river bottom.)
This experiment was repeated, and the same mutations occurred, but in different orders. Also, in one replication, the processing of phosphate was improved by a duplication of the gene that produces phosphatase. This is experimental evidence of an extremely important mechanism in evolutionary history! It is also a particularly elegant experiment because not only was all of this adaptation shown to occur in clonal lines (descended from a single individual), but the authors also determined the exact mutations that caused the improved adaptations by sequencing the genes and proteins involved.
Francis, J.E., & Hansche, P.E. (1972) Directed evolution of metabolic pathways in microbial populations. I. Modification of the acid phosphatase pH optimum in Saccharaomyces cervisiae. Genetics, 70: 59-73.
Francis, J.E., & Hansche, P.E. (1973) Directed evolution of metabolic pathways in microbial populations. II. A repeatable adaptation in Saccharaomyces cervisiae. Genetics, 74:259-265. Hansche, P.E. (1975) Gene duplication as a mechanism of genetic adaptation in Saccharaomyces cervisiae. Genetics, 79: 661-674.
9.)
Changes in the substrate specificities of an enzyme during directed evolution of new functions.
Hall BG
Biochemistry 1981 Jul 7 20:14 4042-9
Abstract
Wild-type ebg enzyme, the second beta-galactosidase of Escherichia coli K12, does not permit growth on lactose. As part of a study of the evolution of new enzymatic functions, I have selected, from a lacZ deletion strain, a variety of spontaneous mutants that grow on lactose and other beta-galactoside sugars. Single point mutations in the structural gene ebgA alter the enzyme so that it hydrolyzes lactose or lactulose effectively; two mutations in ebgA permit galactosylarabinose hydrolysis, while three mutations are required for lactobionic acid hydrolysis. Wild-type ebg enzyme and 16 functional mutant ebg enzymes were purified and analyzed kinetically to determine how the substrate specificities had changed during the directed evolution of these new functions. The specificities for the biologically selected substrates generally increased by at least an order of magnitude via increased Vmax and decreased Km for the substrate. These changes were very specific for the selected substrate, often being accompanied by decreased specificities for other related substrates. The single, double, or triple substitutions in the enzymes did not detectably alter the thermal stability of ebg enzyme.
Yeah, it was, so you obviously didn't look very well, and I guess by accusing me of plagiarizing, your proving your point?
I searched on terms in the text and they didn't show up on the page you linked to. SO do you mind telling me where the text in quotes came from?
With hindsight, how do you determine that their traits gave them competitive advantage?
By allowing them to be more successful at bringing offspring to adulthood.