Behaviour of Saccharomyces boulardii in recurrent Clostridium difficile disease patients.
(17/1198)
BACKGROUND: Despite recent interest in therapeutic microorganisms taken orally, little is known about the pharmacodynamics of these agents in a target population of patients with disease. The present study reports the stool concentrations of Saccharomyces boulardii in a patient population with Clostridium difficile disease (CDD) and correlates stool concentrations with efficacy. METHODS: Patients with recurrent CDD all received a 10-day standard antibiotic regimen together with 28 days of S. boulardii or placebo. Stool samples were collected from patients at various time points and assayed for S. boulardii. RESULTS: The mean concentration of S. boulardii of patients who recurred was 2.5 x 104 CFU/g compared to 1 x 106 CFU/g in patients that did not recur (P=0.02). Patients with low yeast concentrations in their stools (<104/g) recurred more often (14/15, 93%) compared with patients with higher levels (19/35, 54%, P=0.007). Clearance of S. boulardii was rapid; only 4% had positive stools 3 days after stopping dosing. CONCLUSIONS: After chronic dosing of S. boulardii, patients with low stool concentrations had a higher likelihood of recurrence of CDD. Stool concentrations were also lower during periods of diarrhoea. These results show the importance of characterizing the dynamics of a therapeutic microorganism in patients with disease, as kinetic studies in healthy volunteers may not give a true reflection of the disturbed microecology in the disease state. (+info)
Strategies to determine the extent of control exerted by glucose transport on glycolytic flux in the yeast Saccharomyces bayanus.
(18/1198)
The extent to which the transport of glucose across the plasma membrane of the yeast Saccharomyces bayanus controls the glycolytic flux was determined. The magnitude of control was quantified by measuring the effect of small changes in the activity of the glucose transport system on the rate of glucose consumption. Two effectors were used to modulate the activity of glucose transport: (i) maltose, a competitive inhibitor of the glucose transport system in S. bayanus (as well as in Saccharomyces cerevisiae) and (ii) extracellular glucose, the substrate of the glucose transport system. Two approaches were followed to derive from the experimental data the flux control coefficient of glucose transport on the glycolytic flux: (i) direct comparison of the steady-state glycolytic flux with the zero trans-influx of glucose and (ii) comparison of the change in glycolytic flux with the concomitant change in calculated glucose transport activity on variation of the extracellular glucose concentration. Both these approaches demonstrated that in cells of S. bayanus grown on glucose and harvested at the point of glucose exhaustion, a high proportion of the control of the glycolytic flux resides in the transport of glucose across the plasma membrane. (+info)
The primary transcript of the ribosomal repeating unit in yeast.
(19/1198)
Endgroup analysis of 37S ribosomal precursor RNA from Saccharomyces carlsbergensis has revealed that the major 5' endgroup is ppA-Up, with a molar yield of 0.8. This shows that most, if not all, 37S RNA molecules have preserved a transcriptional initiation sequence. Analysis of the 3' terminus of 37S RNA has shown the presence of a uridine rich oligonucleotide, tentatively identified as U6-8-A-NOH. This long stretch of uridines at the 3' end of 37S RNA may represent a transcriptional termination site. The two sets of data on the terminal sequences suggest that 37S ribosomal precursor RNA, if not already spliced, is a primary transcription product. Since the 3' terminus of 26S rRNA, U-U-U-G-UOH., appears to be clearly different from the 3' end of 37S RNA, we conclude that 37S ribosomal precursor RNA contains additional nucleotides 3'-distal to the 26S rRNA sequence. (+info)
Discovery of novel antifungal (1,3)-beta-D-glucan synthase inhibitors.
(20/1198)
The increasing incidence of life-threatening fungal infections has driven the search for new, broad-spectrum fungicidal agents that can be used for treatment and prophylaxis in immunocompromised patients. Natural-product inhibitors of cell wall (1,3)-beta-D-glucan synthase such as lipopeptide pneumocandins and echinocandins as well as the glycolipid papulacandins have been evaluated as potential therapeutics for the last two decades. As a result, MK-0991 (caspofungin acetate; Cancidas), a semisynthetic analogue of pneumocandin B(o), is being developed as a broad-spectrum parenteral agent for the treatment of aspergillosis and candidiasis. This and other lipopeptide antifungal agents have limited oral bioavailability. Thus, we have sought new chemical structures with the mode of action of lipopeptide antifungal agents but with the potential for oral absorption. Results of natural-product screening by a series of newly developed methods has led to the identification of four acidic terpenoid (1,3)-beta-D-glucan synthase inhibitors. Of the four compounds, the in vitro antifungal activity of one, enfumafungin, is comparable to that of L-733560, a close analogue of MK-0991. Like the lipopeptides, enfumafungin specifically inhibits glucan synthesis in whole cells and in (1,3)-beta-D-glucan synthase assays, alters the morphologies of yeasts and molds, and produces a unique response in Saccharomyces cerevisiae strains with point mutations in FKS1, the gene which encodes the large subunit of glucan synthase. (+info)
Enzymatic synthesis of stable, odorless, and powdered furanone glucosides by sucrose phosphorylase.
(21/1198)
Sucrose phosphorylase from Leuconostoc mesenteroides catalyzed transglucosylation from sucrose to 4-hydroxy-3(2H)-furanone derivatives. When 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone or 5-ethyl-4-hydroxy-2-methyl-3(2H)-furanone (EHMF) were used as acceptors, their transfer ratios were more than 45%. In the case of glucosylation of HDMF, the major transfer product was identified as 2,5-dimethyl-3(2H)-furanone 4-O-alpha-D-glucopyranoside (DMF-G). In the case of glucosylation of EHMF, two major transfer products were obtained, and their structures were identified as 2-ethyl-5-methyl-3(2H)-furanone 4-O-alpha-D-glucopyranoside (2E5MF-G) and 5-ethyl-2-methyl-3(2H)-furanone 4-O-alpha-D-glucopyranoside (5E2MF-G) on the bases of spectrometric investigations. These glucosides were more stable than each aglycone. The glucosylated HDMF, DMF-G, was an odorless chemical, on the other hand, HDMF had a pineapple flavor. The glucosylated EHMF (EMF-G) were white odorless powders, though aglycone EHMF was a pale yellow syrup like a caramel with an intense sweet odor. Although DMF-G and EMF-G showed little radical-scavenging activity, hydrolyzates of these glucosides by an intestinal acetone powder from pigs had antioxidative activity as well as their aglycones. It was suggested that these glucosides improved some physical properties and may become prodrugs by glucosylation. (+info)
Highly diverged homologs of Saccharomyces cerevisiae mitochondrial mRNA-specific translational activators have orthologous functions in other budding yeasts.
(22/1198)
Translation of mitochondrially coded mRNAs in Saccharomyces cerevisiae depends on membrane-bound mRNA-specific activator proteins, whose targets lie in the mRNA 5'-untranslated leaders (5'-UTLs). In at least some cases, the activators function to localize translation of hydrophobic proteins on the inner membrane and are rate limiting for gene expression. We searched unsuccessfully in divergent budding yeasts for orthologs of the COX2- and COX3-specific translational activator genes, PET111, PET54, PET122, and PET494, by direct complementation. However, by screening for complementation of mutations in genes adjacent to the PET genes in S. cerevisiae, we obtained chromosomal segments containing highly diverged homologs of PET111 and PET122 from Saccharomyces kluyveri and of PET111 from Kluyveromyces lactis. All three of these genes failed to function in S. cerevisiae. We also found that the 5'-UTLs of the COX2 and COX3 mRNAs of S. kluyveri and K. lactis have little similarity to each other or to those of S. cerevisiae. To determine whether the PET111 and PET122 homologs carry out orthologous functions, we deleted them from the S. kluyveri genome and deleted PET111 from the K. lactis genome. The pet111 mutations in both species prevented COX2 translation, and the S. kluyveri pet122 mutation prevented COX3 translation. Thus, while the sequences of these translational activator proteins and their 5'-UTL targets are highly diverged, their mRNA-specific functions are orthologous. (+info)
The S. pombe orthologue of the S. cerevisiae mob1 gene is essential and functions in signalling the onset of septum formation.
(23/1198)
We have isolated the Schizosaccharomyces pombe orthologue of the Saccharomyces cerevisiae MOB1 gene in a screen designed to enrich for septation mutants. The gene is essential, and cells lacking it display a phenotype typical of septation signalling network mutants. mob1p is located on both spindle pole bodies throughout mitosis. In addition it is also co-localised with the medial ring later in mitosis, and flanks the septum as the medial ring contracts. We also demonstrate that mob1p can be precipitated from cells in a complex with the septation regulating kinase sid2p. (+info)
Evolution and variation of the yeast (Saccharomyces) genome.
(24/1198)
In this review we describe the role of the yeast Saccharomyces in the development of human societies including the use of this organism in the making of wine, bread, beer, and distilled beverages. We also discuss the tremendous diversity of yeast found in natural (i.e., noninoculated) wine fermentations and the scientific uses of yeast over the past 60 years. In conclusion, we present ideas on the model of "genome renewal" and the use of this model to explain the mode by which yeast has evolved and how diversity can be generated. (+info)