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It is generally accepted from the darwinian theory of evolution that a progressive increase in population adaptation will occur in populations containing genetic variation in fitness, until a stable equilibrium is reached and/or the additive genetic variation is exhausted. However, the theoretical literature of population genetics documents exceptions where(More)
AIMS To study the effects of the selenium enrichment protocols in yeast at various points in the cell cycle, total selenium accumulation and the forms of selenium incorporated. METHODS AND RESULTS The use of selenized yeast as enriched selenium supplements in human nutrition has become a topic of increasing interest over the last decade. Four enrichment(More)
Populations of a diploid strain of S. cerevisiae were grown in glucose-limited continuous culture for more than 260 generations. A series of seven sequential adaptive changes were identified by monitoring the frequency of cycloheximide resistance in these populations. Samples were taken from the continuous cultures following each adaptive shift and(More)
Bifidobacterium longum ATCC 15707 cell production was studied in MRS medium supplemented with whey permeate (MRS-WP) during free-cell batch fermentations and continuous immobilized-cell cultures. Very high populations were measured after 12 h batch cultures in MRS-WP medium controlled at pH 5.5 (1.7+/-0.5x10(10) cfu/ml), approximately 2-fold higher than in(More)
The mutation rate to antimycin A resistance was determined for strains of Sacchromyces cerevisiae lacking a functional copy of the structural gene for alcohol dehydrogenase I (ADH1). One type of mutation that can cause antimycin A resistance in these strains is insertion of the transposable element Ty 5' to ADH2, the structural gene for the(More)
Five spontaneous amplifications of the ADH4 gene were identified among 1,894 antimycin A-resistant mutants isolated from a diploid strain after growth at 15 degrees. Four of these amplifications are approximately 40-kb linear extrachromosomal palindromes carrying telomere homologous sequences at each end similar to a previously isolated amplification. ADH4(More)
We report here the use of the ADH4:CUP1 amplification detection system to identify five high amplification rate (HAR) strains of Saccharomyces cerevisiae that display 40- to 600-fold higher amplification rates than those of parental strains. We have identified a mutation in RAD3 DNA repair helicase gene in HAR strain B9-40 that results in a 40-fold increase(More)
Insertion of the transposable element Ty at the ADH4 locus results in increased levels of a new alcohol dehydrogenase (ADH) activity in Saccharomyces cerevisiae. The DNA sequence of this locus has been determined. It contains a long open reading frame which is not homologous to the other ADH isozymes that have been characterized in S. cerevisiae nor does it(More)
A yeast strain lacking a functional copy of ADH1 has been isolated that is resistant to antimycin A because of the presence of multiple copies of a nuclear gene, ADH4. The amplified copies of ADH4 exist on linear molecules 42 kb in length, which can be separated from chromosomal DNA by orthogonal-field-alternation gel electrophoresis. These amplified(More)