Yeast

About: Yeast is a research topic. Over the lifetime, 31777 publications have been published within this topic receiving 868967 citations. The topic is also known as: yeasts.

Production of Resveratrol in Recombinant Microorganisms

Abstract: Resveratrol production in Saccharomyces cerevisiae was compared to that in Escherichia coli. In both systems, 4-coumarate:coenzyme A ligase from tobacco and stilbene synthase from grapes were expressed. When p-coumaric acid was used as the precursor, resveratrol accumulations in the culture medium were observed to be comparable in E. coli (16 mg/liter) and yeast (6 mg/liter).

Protein phosphatase 2A in Saccharomyces cerevisiae: effects on cell growth and bud morphogenesis.

Abstract: We have cloned three genes for protein phosphatases in the yeast Saccharomyces cerevisiae. Two of the genes, PPH21 and PPH22, encode highly similar proteins that are homologs of the mammalian protein phosphatase 2A (PP2A), while the third gene, PPH3, encodes a new PP2A-related protein. Disruptions of either PPH21 or PPH22 had no effects, but spores disrupted for both genes produced very small colonies with few surviving cells. We conclude that PP2A performs an important function in yeast cells. A disruption of the third gene, PPH3, did not in itself affect growth, but it completely prevented growth of spores disrupted for both PPH21 and PPH22. Thus, PPH3 provides some PP2A-complementing activity which allows for a limited growth of PP2A-deficient cells. Strains were constructed in which we could study the phenotypes caused by either excess PP2A or total PP2A depletion. We found that the level of PP2A activity has dramatic effects on cell shape. PP2A-depleted cells develop an abnormal pear-shaped morphology which is particularly pronounced in the growing bud. In contrast, overexpression of PP2A produces more elongated cells, and high-level overexpression causes a balloonlike phenotype with huge swollen cells filled by large vacuoles.

Hydrocarbon degradation and enzyme activities of cold-adapted bacteria and yeasts

Abstract: The potential of 89 culturable cold-adapted isolates from uncontaminated habitats, including 61 bacterial and 28 yeast strains, to utilize representative fractions of petroleum hydrocarbons (n-alkanes, monoaromatic and polycyclic aromatic hydrocarbons) for growth and to produce various enzymes at 10 degrees C was investigated. The efficiency of bacterial and yeast strains was compared. The growth temperature range of the yeast strains was significantly smaller than that of the bacterial strains. Sixty percent of the yeasts but only 8% of the bacteria could be classified as true psychrophiles, showing no growth above 20 degrees C. A high percentage (89%) of the yeast strains showed lipase activity. More than one-third of the 61 bacterial strains produced amylase, beta-lactamase, beta-galactosidase or lipase; more than two-thirds were protease producers. Only 6% of the bacterial strains but 79% of the yeast strains utilized n-hexadecane for growth; 13% of the bacterial strains and 21-32% of the yeast strains utilized phenol, phenanthrene or anthracene for growth. Only four yeast strains but none of the bacterial strains could grow with all hydrocarbons tested. The biodegradation of phenol was investigated in fed-batch cultures at 10 degrees C. Three yeast strains degraded phenol concentrations as high as 10 mM (one strain) or 12.5 mM (two strains). Of eight bacterial strains, two strains degraded up to 10 mM phenol. The optimum temperature for phenol degradation was 20 degrees C for all eight bacterial strains and for two yeast strains. Biodegradation by five yeast strains was optimal at 10 degrees C and faster at 1 degrees C than at 20 degrees C. All phenol-degrading strains produced catechol 1,2 dioxygenase activity.

Regulation of genes controlling synthesis of the galactose pathway enzymes in yeast

Abstract: HE genetic control of synthesis of the galactose pathway enzymes in Saccharomyces cerevisiae conforms in certain respects to the operon model proposed by JACOB and MONOD (1961) for the ,&galactosidase system of E. coli, and shown by BUTTIN (1963a, b) to be valid for the E. coli galactose system as well. Three closely linked structural genes specify the galactose pathway enzymes, galactokinase, galactose-1-phosphate-uridyl transferase (transferase), and uridine diphosphogalactose-4-epimerase (epimerase) (DOUGLAS and HAWTHORNE 1964). The three loci are under the control of an unlinked regulator gene, i, which is recognizable by its recessive mutations that permit constitutive synthesis of the three galactose enzymes (DOUGLAS and PELROY 1963). A key feature of the bacterial systems which appears to be absent in the yeast system in the close association of an operator gene with the structural genes (DOUGLAS and HAWTHORNE 1964). The operator locus was defined originally as a region linked to the structural genes in which two types of mutations occurred: O\", which were expressed as cis-dominant for constitutive synthesis of the operon proteins, and Oo, which prevented synthesis of all of the proteins of the operon. JACOB and MONOD (1965) have redefined the operator locus in the p-galactosidase system of E. coli as the site of repressor recognition identified by 0\" mutations. The 0\" mutations in this system are now considered to be polarity mutations within the first structural gene of the operon (BECKWITH 1964). Mutations in yeast that result in failure to synthesize the three galactose enzymes and thus resemble phenotypically mutations of the Oo type can be readily isolated. However, these are not polarity mutants nor are they mutants in which inducer uptake or metabolism is defective. They map in the GA, locus which segregates independently of the galactose structural genes and their phenotype is unchanged in combination with i(DOUGLAS and HAWTHORNE 1964). The occurrence of mutations in the yeast galactose system which display the dominant constitutive phenotype and the relationship of these mutants to the GA, region and to the structural genes for the galactose enzymes is the subject of the present paper.