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PubMed2001

Detection of anti-Saccharomyces cerevisiae antibodies in Crohn's disease: is it a reliable diagnostic and prognostic marker?

BACKGROUND: In the past few years, serologic markers have been proposed in inflammatory bowel disease. Anti-Saccharomyces cerevisiae antibodies showed high specificity for Crohn's disease. A prognostic role for serology has also been hypothesised. AIMS: To evaluate anti-Saccharomyces cerevisiae antibody distribution in an unselected Italian inflammatory bowel disease population. To analyse whether anti-Saccharomyces cerevisiae antibody status (positive/negative) and/or anti-Saccharomyces cerevisiae antibody titres are associated with clinical variables and outcome measures in Crohn's disease patients. PATIENTS AND METHODS: A series of 299 inflammatory bowel disease patients were evaluated; serum samples were taken and a short clinical history was recorded. anti-Saccharomyces cerevisiae antibodies IgG enzyme-linked immunosorbent assay Medilab (Milan, Italy) kit was used in order to determine anti-Saccharomyces cerevisiae antibody status. RESULTS: Sensitivity, specificity and likelihood ratio for positive test in the differential diagnosis of inflammatory bowel disease was 59%, 89%, 8.1, respectively. Clinical variables significantly associated with anti-Saccharomyces cerevisiae antibody status in logistic regression were found to be ileal location (p=0.01) and earlier age at diagnosis (p<0.01). Among ileal Crohn's disease patients, there was a trend in concordance between anti-Saccharomyces cerevisiae antibody titres and higher number of surgical procedures which was not statistically significant applying more complex statistics. CONCLUSIONS: In an Italian inflammatory bowel disease population, anti-Saccharomyces cerevisiae antibodies status showed characteristics similar to those previously reported. Anti-Saccharomyces cerevisiae antibody positivity is associated with ileal involvement and with earlier onset of Crohn's disease.

Adult↗

PubMed1998

Phylogenetic analysis of the Saccharomyces cerevisiae group based on polymorphisms of rDNA spacer sequences.

The phylogenetic relationships between species of yeasts assigned to the Saccharomyces sensu stricto group, which includes Saccharomyces cerevisiae and Saccharomyces bayanus, were studied together with Saccharomyces pastorianus and Saccharomyces paradoxus. The experimental approaches used were RFLP analysis of the PCR-amplified rDNA internal transcribed spacer (ITS) and intergenic spacer, and total ITS sequence analysis. Both RFLP and sequence analyses gave fairly similar results. The gene trees generated with either of the two data sets showed the distribution of the yeasts into two major, well-separated, phylogenetic clusters called 'cerevisiae' and 'bayanus'. The 'cerevisiae' cluster included the S. cerevisiae type strain, together with most of the species (16 out of 23), whereas the 'bayanus' cluster included the remaining seven type strains. Therefore, analysis of rDNA sequences confirmed S. cerevisiae and S. bayanus as two well-defined taxa. However, S. pastorianus and S. paradoxus, the two other usually accepted taxa of the now-defined Saccharomyces sensu stricto complex, could not be clearly separated from S. bayanus and S. cerevisiae, respectively. However, in both PCR-RFLP and ITS sequence analyses, S. paradoxus had the outermost position in the 'cerevisiae' cluster. PCR-RFLP analysis of the ribosomal spacer sequences was also carried out on 26 Saccharomyces strains isolated in various wine-growing regions of France in an attempt to clarify their positions in the Saccharomyces phylogenetic tree. Compared to the diversity of the Saccharomyces type strains, less genetic diversity was detected among these yeasts and several of them exhibited identical RFLP patterns. Most of the wine yeast strains (16 out of 26) were closely related to each other and were found within the 'cerevisiae' cluster. The remaining 10 wine yeast strains branched within the 'bayanus' cluster. PCR-RFLP analysis of ribosomal spacer sequences thus appears to be a useful and appropriate method for the correct characterization of Saccharomyces yeast strains used in food processing.

DNA, Fungal↗

PubMed1999

Successful design and development of genetically engineered Saccharomyces yeasts for effective cofermentation of glucose and xylose from cellulosic biomass to fuel ethanol.

Ethanol is an effective, environmentally friendly, nonfossil, transportation biofuel that produces far less pollution than gasoline. Furthermore, ethanol can be produced from plentiful, domestically available, renewable, cellulosic biomass. However, cellulosic biomass contains two major sugars, glucose and xylose, and a major obstacle in this process is that Saccharomyces yeasts, traditionally used and still the only microorganisms currently used for large scale industrial production of ethanol from glucose, are unable to ferment xylose to ethanol. This makes the use of these safest, most effective Saccharomyces yeasts for conversion of biomass to ethanol economically unfeasible. Since 1980, scientists worldwide have actively been trying to develop genetically engineered Saccharomyces yeasts to ferment xylose. In 1993, we achieved a historic breakthrough to succeed in the development of the first genetically engineered Saccharomyces yeasts that can effectively ferment both glucose and xylose to ethanol. This was accomplished by carefully redesigning the yeast metabolic pathway for fermenting xylose to ethanol, including cloning three xylose-metabolizing genes, modifying the genetic systems controlling gene expression, changing the dynamics of the carbon flow, etc. As a result, our recombinant yeasts not only can effectively ferment both glucose and xylose to ethanol when these sugars are present separately in the medium, but also can effectively coferment both glucose and xylose present in the same medium simultaneously to ethanol. This has made it possible because we have genetically engineered the Saccharomyces yeasts as such that they are able to overcome some of the natural barrier present in all microorganisms, such as the synthesis of the xylose metabolizing enzymes not to be affected by the presence of glucose and by the absence of xylose in the medium. This first generation of genetically engineered glucose-xylose-cofermenting Saccharomyces yeasts relies on the presence of a high-copy-number 2 mu-based plasmid that contains the three cloned genetically modified xylose-metabolizing genes to provide the xylose-metabolizing capability. In 1995, we achieved another breakthrough by creating the super-stable genetically engineered glucose-xylose-cofermenting Saccharomyces yeasts which contain multiple copies of the same three xylose-metabolizing genes stably integrated on the yeast chromosome. This is another critical development which has made it possible for the genetically engineered yeasts to be effective for cofermenting glucose and xylose by continuous fermentation. It is widely believed that the successful development of the stable glucose-xylose-cofermenting Saccharomyces yeasts has made the biomass-to-ethanol technology a step much closer to commercialization. In this paper, we present an overview of our rationales and strategies as well as our methods and approaches that led to the ingenious design and successful development of our genetically engineered Saccharomyces yeasts for effective cofermentation of glucose and xylose to biofuel ethanol.

Biomass↗

PubMed2001

Transformation systems of non-Saccharomyces yeasts.

This review describes the transformation systems including vectors, replicons, genetic markers, transformation methods, vector stability, and copy numbers of 13 genera and 31 species of non-Saccharomyces yeasts. Schizosaccharomyces pombe was the first non-Saccharomyces yeast studied for transformation and genetics. The replicons of non-Saccharomyces yeast vectors are from native plasmids, chromosomal DNA, and mitochondrial DNA of Saccharomyces cerevisiae, non-Saccharomyces yeasts, protozoan, plant, and animal. Vectors such as YAC, YCp, YEp, YIp, and YRp were developed for non-Saccharomyces yeasts. Forty-two types of genes from bacteria, yeasts, fungi, and plant were used as genetic markers that could be classified into biosynthetic, dominant, and colored groups to construct non-Saccharomyces yeasts vectors. The LEU2 gene and G418 resistance gene are the two most popular markers used in the yeast transformation. All known transformation methods such as spheroplast-mediating method, alkaline ion treatment method, electroporation, trans-kingdom conjugation, and biolistics have been developed successfully for non-Saccharomyces yeasts, among which the first three are most widely used. The highest copy number detected from non-Saccharomyces yeasts is 60 copies in Kluyveromyces lactis. No general rule is known to illustrate the transformation efficiency, vector stability, and copy number, although factors such as vector composition, host strain, transformation method, and selective pressure might influence them.

Genetic Markers↗

PubMed1999

Karyotypes of Saccharomyces sensu lato species.

An improved pulsed-field electrophoresis program was developed to study differently sized chromosomes within the genus Saccharomyces. The number of chromosomes in the type strains was shown to be nine in Saccharomyces castellii and Saccharomyces dairenensis, 12 in Saccharomyces servazzii and Saccharomyces unisporus, 16 in Saccharomyces exiguus and seven in Saccharomyces kluyveri. The sizes of individual chromosomes were resolved and the approximate genome sizes were determined by the addition of individual chromosomes of the karyotypes. Apparently, the genome of S. exiguus, which is the only Saccharomyces sensu lato yeast to contain small chromosomes, is larger than that of Saccharomyces cerevisiae. On the other hand, other species exhibited genome sizes that were 10-25% smaller than that of S. cerevisiae. Well-defined karyotypes represent the basis for future genome mapping and sequencing projects, as well as studies of the origin of the modern genomes.

Chromosomes, Fungal↗

PubMedDate not supplied

Antibodies to Saccharomyces cerevisiae: are they useful in clinical practice?

BACKGROUND/AIMS: Antibodies to Saccharomyces cerevisiae are associated with Crohn's disease. The aim of this study was to assess the sensitivity and specificity of antibodies to Saccharomyces cerevisiae for Crohn's disease in an Italian population and to evaluate their clinical role. METHODOLOGY: Antibodies to Saccharomyces cerevisiae serum levels were assessed in 72 inflammatory bowel disease patients (30 Crohn's disease; 42 ulcerative colitis) and 35 age-matched controls. Patients were divided into subgroups on the basis of disease behavior and clinical feature were evaluated. RESULTS: Antibodies to Saccharomyces cerevisiae sensitivity and specificity for Crohn's disease patients were 50% (31-68) and 91% (77-98), for IgG and 56% (37-64) and 94% (80-99), respectively, for IgA. No correlation was observed between the presence of antibodies to Saccharomyces cerevisiae and clinical features. Antibodies to Saccharomyces cerevisiae were more prevalent in Crohn's disease than in ulcerative colitis patients (IgA: 57% vs. 26%; IgG: 50% vs. 17%; p < 0.05). Interestingly, in Crohn's disease patients, the prevalence of antibodies to Saccharomyces cerevisiae was higher in patients with small bowel involvement than in patients with pure colonic disease (IgA: 66% vs. 17%; IgG: 58% vs. 17%). No difference in antibodies to Saccharomyces cerevisiae prevalence was observed between ulcerative colitis and pure colonic Crohn's disease patients. CONCLUSIONS: Our data show an association between Crohn's disease and antibodies to Saccharomyces cerevisiae. However, it does not seem useful in discriminating between ulcerative colitis and colic Crohn's disease.

Adult↗

PubMed2002

Diagnostic role of anti-Saccharomyces cerevisiae mannan antibodies combined with antineutrophil cytoplasmic antibodies in patients with inflammatory bowel disease.

PURPOSE: Perinuclear antineutrophil cytoplasmic autoantibody is known to be a marker for ulcerative colitis, and anti-Saccharomyces cerevisiae Mannan antibody is a serologic marker associated with Crohn's disease. The aim of this study was to assess the value of detecting perinuclear antineutrophil cytoplasmic autoantibody and/or anti-Saccharomyces cerevisiae Mannan antibody for the diagnosis of ulcerative colitis, Crohn's disease, Behçet's colitis, and tuberculous colitis. METHODS: Serum samples were obtained from 85 patients with Crohn's disease, 77 with ulcerative colitis, 36 with Behçet's colitis, 14 with tuberculous colitis, 20 healthy controls, and 21 first-degree relatives of patients with Crohn's disease. Determination of perinuclear antineutrophil cytoplasmic autoantibody and anti-Saccharomyces cerevisiae Mannan antibody was performed with the standardized indirect immunofluorescence technique and an enzyme-linked immunosorbent assay, respectively. RESULTS: A relatively high percentage of patients with Crohn's disease (49.4 percent), relatives of Crohn's disease patients (61.9 percent), and patients with Behçet's disease (41.7 percent) tested seropositive for anti-Saccharomyces cerevisiae Mannan antibody compared with normal controls (10 percent). In cases of ulcerative colitis, 44.2 percent tested seropositive for perinuclear antineutrophil cytoplasmic autoantibody, whereas the controls showed 0 percent positivity. The combination of a positive anti-Saccharomyces cerevisiae Mannan antibody test and a negative perinuclear antineutrophil cytoplasmic autoantibody yielded a sensitivity and specificity of 48.2 and 87 percent, respectively, for Crohn's disease. The combination of a positive perinuclear antineutrophil cytoplasmic autoantibody test and a negative anti-Saccharomyces cerevisiae Mannan antibody test yielded a sensitivity and specificity of 36.4 and 97.6 percent, respectively, for ulcerative colitis. CONCLUSION: Anti-Saccharomyces cerevisiae Mannan antibody may be associated with Crohn's disease and Behçet's disease and perinuclear antineutrophil cytoplasmic autoantibody with ulcerative colitis. A combination of both tests may aid the differential diagnosis of inflammatory bowel disease.

Adult↗

PubMed1998

Intergenic transcribed spacer PCR ribotyping for differentiation of Saccharomyces species and interspecific hybrids.

The taxonomy of the genus Saccharomyces has undergone significant changes recently with the use of genotypic rather than phenotypic methods for the identification of strains to the species level. The sequence of rRNA genes has been utilized for the identification of a variety of fungi to the species level. This methodology, applied to species of Saccharomyces, allows unknown Saccharomyces isolates to be assigned to the type strains. It was the aim of the present study to assess whether typing of the intergenic spacer region by using restriction fragment length polymorphisms of PCR products (intergenic transcribed spacer PCR [ITS-PCR] ribotyping) could distinguish among type strains of the 10 accepted species of Saccharomyces and further to assess if this method could distinguish strains that were interspecific hybrids. Cellular DNA, isolated after the lysis of protoplasts, was amplified by PCR using ITS1 and ITS4 primers, purified by liquid chromatography, and digested with restriction endonucleases. Ribotyping patterns using the restriction enzymes MaeI and HaeIII could distinguish all species of Saccharomyces from each other, as well as from Candida glabrata, Candida albicans, and Blastomyces dermatitidis. The only exception to this was the inability to distinguish between Saccharomyces bayanus and S. pastorianus (S. carlsbergensis). Furthermore, interspecific hybrids resulting from the mating of sibling species of Saccharomyces were shown to share the ITS-PCR ribotyping patterns of both parental species. It should now be possible, by this simple PCR-based technique, to accurately identify these strains to the species level, thereby allowing an increase in our understanding of the characteristics required by these interspecific hybrids for their particular ecological niches.

DNA, Fungal↗

PubMed1996

Phylogenetic relationships of species of the genus Saccharomyces Meyen ex Reess deduced from partial base sequences of 18S and 26S ribosomal RNAs (saccharomycetaceae).

In order to clarify the phylogenetic relationships among the yeast species classified in the genus Saccharomyces, partial base sequences of 18S and 26S ribosomal RNAs were determined for ten selected strains. The regions determined correspond to positions 1451 through 1618 of the 18S rRNA and positions 493 through 622 and 1611 through 1835 of the 26S rRNA in S. cerevisiae. Analyses of these partial base sequences suggested that the genus Saccharomyces is phylogenetically heterogeneous. Saccharomyces servazzii and S. unisporus showed identical or very similar sequences in all the three regions, and their phylogenetic distance from S. cerevisiae was large enough to introduce a genus independent of Saccharomyces. Saccharomyces kluyveri is also distant from all the other Saccharomyces species examined, and is likely to deserve a new genus. Estimated phylogenetic relationships between Saccharomyces and other genera characterized by the Q-6 system, such as species of Zygosaccharomyces. Torulaspora, Kluyveromyces, Arxiozyma, Pachytichospora, Nadsonia. Hanseniaspora, Kloeckeraspora, and Saccharomycodes, are also discussed.

Base Sequence↗

PubMed2000

Phenotypic and genetic diversity of Saccharomyces contaminants isolated from lager breweries and their phylogenetic relationship with brewing yeasts.

A taxonomic study was carried out for isolates of Saccharomyces spp. identified as contaminants ("wild yeast") in 24 different lager breweries. With reference to the current taxonomy all isolates were found to belong to the Saccharomyces sensu stricto complex and 58% of the isolates were further identified as S. cerevisiae, 26% as S. pastorianus and 3% as S. bayanus. The remaining isolates (13%) could not be identified to the species level based on their phenotypic characteristics. However, some of these isolates were identified as S. cerevisiae by HaeIII restriction digest of PCR-amplified intergenic transcribed spacer (ITS) regions. Chromosome length polymorphism (CLP) was evident among the Saccharomyces brewing contaminants with chromosome profiles typical of Saccharomyces sensu stricto. Based upon cluster analysis of their chromosome profiles the majority of the brewing contaminants could be grouped as either S. cerevisiae or S. pastorianus/S. bayanus. Further, the technique was able to differentiate between almost all brewing contaminants and to separate them from any specific lager brewing yeast. The diversity of the Saccharomyces brewing contaminants clearly demonstrated by their CLP was further reflected by MAL genotyping. For the majority of the isolates more than two MAL loci were found with MAL1, MAL2 MAL3, MAL4 and MAL11, MAL31, MAL41 as the dominant genotypes. For all isolates MAL11 and MAL31 were found whereas MAL61 only was found for one isolate. The high number of MAL loci found in the SaccharomYces brewing contaminants indicate their adaptation to a maltose-enriched environment.

Beer↗

PubMed2001

Taxonomical and technological characteristics of Saccharomyces spp. associated with blue veined cheese.

In blue veined cheeses, the dominant yeast species in most cases is Debaryomyces hansenii. Saccharomyces spp. occurs less frequently, but they can be found in some blue veined cheeses. In the present study, the taxonomy of Saccharomyces spp. associated to blue veined cheeses was studied and comparisons made to type strains of Saccharomyces spp. and starter cultures of Saccharomyces spp. used in other food fermentations. Phenotypically, the cheese strains were referred to the Saccharomyces sensu stricto complex and were further identified as S. cerevisiae. Genotypically, the Saccharomyces spp. investigated were similar although chromosomal polymorphism were observed. Concerning the technological characteristics, they were similar in assimilation and fermentation of the residual sugars and organic acids naturally found in cheese. The investigated yeasts were also similar in their lipolytic activity being able to hydrolyse tributyrin and low chain (C:8), but not C:14 fatty acids. However, they differed in their tolerance to NaCl with the blue cheese strains showing a higher tolerance. The cheese strain S. cerevisiae FB 7 was the only yeast capable of degrading casein. It mainly degraded the alpha(s1)-casein and the beta(alpha2)-casein components. It was also the only isolate stimulating the development of Penicillium roqueforti in cheese agar imitating the conditions in blue veined cheese. The stimulation of P. roqueforti was most pronounced for the least proteolytic strain of P. roqueforti examined.

Cheese↗

PubMed1999

Effect of Saccharomyces boulardii on cAMP- and Ca2+ -dependent Cl- secretion in T84 cells.

Several reports have confirmed that the cooperative interaction between cAMP- and Ca2+-mediated transduction pathways may contribute to the stimulatory or inhibitory regulation of Cl- secretion in intestinal epithelium. Saccharomyces boulardii has been shown to inhibit cholera toxin-induced secretion in rat jejunum. We have identified a 120-kDa protein in medium conditioned by Saccharomyces boulardii that reduces cholera toxin-induced cAMP in intestinal cells. The present study evaluated the effect of medium conditioned by Saccharomyces boulardii on cAMP- and Ca2+-mediated Cl- secretion in T84 cells. Experiments performed with cAMP agonists revealed that 1 hr of preincubation of cells with medium conditioned by Saccharomyces boulardii was necessary to elicit a 40-50% reduction in receptor (cholera toxin, prostaglandin E2, and vasoactive intestinal polypeptide) and nonreceptor (forskolin) mediated cAMP synthesis and 125I efflux. Secretion induced by carbachol was inhibited when cells were pretreated for 1 hr with medium conditioned by Saccharomyces boulardii despite the absence of inhibition of Ins (1,4,5)P3. From this study we conclude that Saccharomyces boulardii exerts an inhibitory effect in vitro on Cl- secretion mediated through both cAMP- and Ca2+-mediated signaling pathways.

Animals↗

PubMed2005

Invasive Saccharomyces infection: a comprehensive review.

BACKGROUND: Saccharomyces cerevisiae (also known as "baker's yeast" or "brewer's yeast") is mostly considered to be an occasional digestive commensal. However, since the 1990s, there have been a growing number of reports about its implication as an etiologic agent of invasive infection. A particular feature of such infections is their association with a probiotic preparation of Saccharomyces boulardii (a subtype of S. cerevisiae) for treatment various diarrheal disorders. METHODS: We collected published case reports, through May 2005, of invasive Saccharomyces infection by use of a Medline query. Epidemiological and clinical charts and therapeutic strategies were analyzed. RESULTS: We found 92 cases of Saccharomyces invasive infection. Predisposing factors were similar to those of invasive candidiasis, with intravascular catheter and antibiotic therapy being the most frequent. Blood was the most frequent site of isolation (for 72 patients). S. boulardii accounted for 51.3% of fungemias and was exclusively isolated from blood. Compared with patients infected with S. cerevisiae, patients infected with S. boulardii were more frequently immunocompetent and had a better prognosis. Saccharomyces invasive infection was clinically indistinguishable from an invasive candidiasis. Overall, S. cerevisiae clinical isolates exhibited low susceptibility to amphotericin B and azole derivatives. However, global outcome was favorable in 62% of the cases. Treatment with intravenous amphotericin B and fluconazole, in combination with central vascular catheter removal, were effective therapeutic options. CONCLUSION: Saccharomyces organisms should now be added to the growing list of emerging fungal pathogens. Special caution should be taken regarding the use of S. boulardii probiotic preparations.

Female↗

PubMed2002

Evidence for multiple interspecific hybridization in Saccharomyces sensu stricto species.

Fluorescent amplified fragment length polymorphism analysis demonstrates a high level of gene exchange between Saccharomyces sensu stricto species, with some strains having undergone multiple interspecific hybridization events with subsequent changes in genome complexity. Two lager strains were shown to be hybrids between Saccharomyces cerevisiae and the alloploid species Saccharomyces pastorianus. The genome structure of CBS 380(T), the type strain of Saccharomyces bayanus, is also consistent with S. pastorianus gene transfer. The results indicate that the cider yeast, CID1, possesses nuclear DNA from three separate species. Mating experiments show that there are no barriers to interspecific conjugation of haploid cells. Furthermore, the allopolyploid strains were able to undergo further hybridizations with other Saccharomyces sensu stricto yeasts. These results demonstrate that introgression between the Saccharomyces sensu stricto species is likely.

Beer↗

PubMed2004

Antineutrophil cytoplasmic autoantibodies and anti-Saccharomyces cerevisiae antibodies in inflammatory bowel diseases.

BACKGROUND/AIMS: Perinuclear antineutrophil cytoplasmic autoantibody is a marker for ulcerative colitis, and anti-Saccharomyces cerevisiae antibody is known to be associated with Crohn's disease. The purpose of this study was to search the value of detecting perinuclear antineutrophil cytoplasmic autoantibody and anti-Saccharomyces cerevisiae antibody for the diagnosis of Turkish inflammatory bowel disease patients. METHODS: Serum samples were obtained from 80 patients with ulcerative colitis, 61 patients with Crohn's disease and 40 healthy controls. Determination of both anti-Saccharomyces cerevisiae antibody and antineutrophil cytoplasmic autoantibody was performed with the standardized enzyme-linked immunosorbent assay. RESULTS: In cases with ulcerative colitis, 65% tested seropositive for antineutrophil cytoplasmic autoantibody, whereas the controls showed 2.5% positivity. In cases with Crohn's disease, 63.9% tested seropositive for anti-Saccharomyces cerevisiae antibody, whereas the controls showed 2.5% seropositivity. The combination of a positive anti-Saccharomyces cerevisiae antibody test and a negative antineutrophil cytoplasmic autoantibody yielded a sensitivity and specificity of 32.0% and 97.5%, respectively. The combination of a positive perinuclear antineutrophil cytoplasmic autoantibody and a negative anti-Saccharomyces cerevisiae antibody test yielded a sensitivity and specificity of 44.2% and 97.5%, respectively. CONCLUSIONS: Both serologic tests may aid in the differential diagnosis of inflammatory bowel disease.

Adolescent↗

PubMed2004

Characterization of the effectiveness of hexose transporters for transporting xylose during glucose and xylose co-fermentation by a recombinant Saccharomyces yeast.

We have developed recombinant Saccharomyces yeasts that can effectively co-ferment glucose and xylose to ethanol. However, these yeasts still ferment glucose more efficiently than xylose. The transport of xylose could be one of the steps limiting the fermentation of xylose. In this study, we characterized the changes in the expression pattern of the hexose transporter and related genes during co-fermentation of glucose and xylose using one of our recombinant yeasts, Saccharomyces cerevisiae 424A(LNH-ST). The transcription of the hexose transporter and related genes was strongly influenced by the presence of glucose; HXT1, HXT2 and HXT3 were greatly activated by glucose and HXT5, HXT7 and AGT1 were significantly repressed by glucose. We also examined the effectiveness of individual transporters encoded by HXT1, HXT2, HXT4, HXT5, HXT7 and GAL2 genes for transporting xylose during co-fermentation of glucose and xylose in a Saccharomyces hxt degrees mutant (RE700A). We compared these hxt degrees derivatives to RE700A wild-type strain (S. cerevisiae MC996A) where all of them contained the same xylose metabolizing genes present in our xylose-fermenting yeasts such as 424A(LNH-ST). Our results showed that recombinant RE700A containing the cloned HXT7 or HXT5 were substantially more effective for fermenting xylose to ethanol. In addition, we found that the efficiency of transporters for intracellular accumulation of xylose was as follows: HXT7 > HXT5 > GAL2 > WT > HXT1 > HXT4 > > > RE700A. Furthermore, we provided evidence that the Saccharomyces galactose transporter system could be a highly effective xylose transporter. The information reported here should be of great importance for improving the Saccharomyces yeast transport of xylose.

Fermentation↗

PubMed1982

The anaerobic metabolism of malate of Saccharomyces bailii and the partial purification and characterization of malic enzyme.

1. The main pathway of the anaerobic metabolism of L-malate in Saccharomyces bailii is catalyzed by a L-malic enzyme. 2. The enzyme was purified more than 300-fold. During the purification procedure fumarase and pyruvate decarboxylase were removed completely, and malate dehydrogenase and oxalacetate decarboxylase were removed to a very large extent. 3. Manganese ions are not required for the reaction of malic enzyme of Saccharomyces bailii, but the activity of the enzyme is increased by manganese. 4. The reaction of L-malic enzyme proceeds with the coenzymes NAD and (to a lesser extent) NADP. 5. The Km-values of the malic enzyme of Saccharomyces bailii were 10 mM for L-malate and 0.1 mM for NAD. 6. A model based on the activity and substrate affinity of malic enzyme, the intracellular concentration of malate and phosphate, and its action on fumarase, is proposed to explain the complete anaerobic degradation of malate in Saccharomyces bailii as compared with the partial decomposition of malate in Saccharomyces cerevisiae.

Anaerobiosis↗

PubMed1994

Replacement of the Saccharomyces cerevisiae RPR1 gene with heterologous RNase P RNA genes.

Phylogenetic studies of yeast nuclear RNase P RNA genes have shown a striking conservation of secondary structure for the Saccharomyces and Schizosaccharomyces RNase P RNAs, yet much of the primary sequence and many substructures vary among the RNAs examined. To investigate which sequences and structural features can be varied and still allow function in a heterologous organism, RNase P genes from several yeast species were tested for the ability to substitute for the Saccharomyces cerevisiae RNA. The RNase P genes from Saccharomyces carlsbergensis and Saccharomyces kluyveri could act as the sole source of RNase P RNA within S. cerevisiae cells, whereas the genes from Saccharomyces globosus and Schizosaccharomyces pombe could not. Although heterologous RNase P RNAs were synthesized by the cells in all cases, the RNAs that complemented tended to be processed from longer precursor transcripts into mature-sized RNase P RNA, while the RNAs that did not complement tended to accumulate as the longer precursor form. The results identified sequences and structures in the RNA that are not essential for interaction with species-specific proteins, processing or localization, and suggested other positions that may be candidates for such processes.

Base Sequence↗