Authentication of ATCC strains in theSaccharomyces cerevisiae complex by PCR fingerprinting

Restriction fragment length polymorphisms in the rDNA internal transcribed spacer region (ITS) of 18 yeast strains currently assigned toSaccharomyces cerevisiae, S. pastorianus, andS. bayanus were examined. Primers complementary to the ITS region were used to amplify the ITS rDNA by the polymerase chain reaction (PCR). The products were digested with 10 endonucleases and cluster analysis was used to generate a phenogram from the restriction fragment data. Three strains ofS. cerevisiae (ATCC 10609, 26250, and 66162) exhibited restriction patterns that were different from the type strain but identical to those of theS. bayanus-S. pastorianus cluster. In contrast,S. pastorianus (ATCC 76671) showed restriction profiles that were different from its type strain but were identical to the type strain ofS. cerevisiae (ATCC 18824). These results suggest that the three strains ofS. cerevisiae should be reassigned to eitherS. pastorianus orS. bayanus, and the strain ofS. pastorianus (ATCC 76671) should be reclassified asS. cerevisiae.     

Molecular characterization and identification ofSaprolegnia by restriction analysis of genes coding for ribosomal RNA

Restriction fragment length polymorphisms (RFLPs) in two regions of the ribosomal DNA (rDNA) repeat unit were examined in 33 strains representing 18 species ofSaprolegnia. The Polymerase Chain Reaction (PCR) was used to separately amplify the 18S rDNA and the region spanning the two internal transcribed spacers (ITS) and the 5.8S ribosomal RNA gene. Amplified products were subjected to a battery of restriction endonucleases to generate various fingerprints. The internal transcribed spacer region exhibited more variability than the 18S rDNA and yielded distinctive profiles for most of the species examined. Most of the species showing 100% similarity for the 18S rDNA could be distinguished by 5.8S + ITS restriction polymorphisms except forS. hypogyna, S. delica, S. lapponica, andS. mixta. The rDNA data indicate thatS. lapponica andS. mixta are conspecific withS. ferax, whereas there is no support for the proposed synonymies ofS. diclina withS. delica and ofS. mixta withS. monoica. Results from cluster analysis of the two data sets were very consistent and tree topologies were the same, regardless of the clustering method used. A further examination of multiple strains in theS. diclina-S. parasitica complex showed that restriction profiles are conserved across different strains ofS. parasitica originating from the U.K. and Japan.HhaI andBsaI restriction polymorphisms were observed in isolates from the U.S. and India. The endonucleaseBstUI was diagnostic forS. parasitica, generating identical fingerprints for all strains regardless of host and geographic origin. Except for the atypical strain ATCC 36144, restriction patterns were also largely conserved inS. diclina. Correlation of the rDNA data with morphological and ultrastructural features showed thatS. diclina andS. parasitica are not conspecific. Restriction polymorphisms in PCR-amplified rDNA provide a molecular basis for the classification ofSaprolegnia and will be useful for the identification of strains that fail to produce antheridia and oogonia.     

RFLP analysis of the ribosomal internal transcribed spacers and the 5.8S rRNA gene region of the genus Saccharomyces: a fast method for species identification and the differentiation of flor yeasts

The PCR amplification and subsequent restriction analysis of the region spanning the internal transcribed spacers (ITS1 and ITS2) and the 5.8S rRNA gene was applied to the identification of yeasts belonging to the genus Saccharomyces. This methodology has previously been used for the identification of some species of this genus, but in the present work, this application was extended to the identification of new accepted Saccharomyces species (S. kunashirensis, S. martiniae, S. rosinii, S. spencerorum, and S. transvaalensis), as well as to the differentiation of an interesting group of Saccharomyces cerevisiae strains, known as flor yeasts, which are responsible for ageing sherry wine. Among the species of the Saccharomyces sensu lato complex, the high diversity observed, either in the length of the amplified region (ranged between 700 and 875 bp) or in their restriction patterns allows the unequivocal identification of these species. With respect to the four sibling species of the Saccharomyces sensu stricto complex, only two of them, S. bayanus and S. pastorianus, cannot be differentiated according to their restriction patterns, which is in accordance with the hybrid origin (S. bayanus × S. cerevisiae) of S. pastorianus. The flor S. cerevisiae strains exhibited restriction patterns different from those typical of the species S. cerevisiae. These differences can easily be used to differentiate this interesting group of strains. We demonstrate that the specific patterns exhibited by flor yeasts are due to the presence of a 24-bp deletion located in the ITS1 region and that this could have originated as a consequence of a slipped-strand mispairing during replication or be due to an unequal crossing-over. A subsequent restriction analysis of this region from more than 150 flor strains indicated that this deletion is fixed in flor yeast populations.     

Molecular diversity of oligotrophic and neurotropic members of the black yeast genus Exophiala,with accent on E. dermatitidis

Analysis of ITS rDNA of the black yeast Exophiala dermatitidis revealed a close phylogenetic relationship to the meristematic fungus Sarcinomyces phaeomuriformis. As most strains ofS. phaeomuriformis have a yeast-like phenotype corresponding to the anamorph genus Exophiala, a new combination in Exophiala is proposed. On the basis of ITS sequence, M-13 fingerprint and SSU intron data, two main entities could be distinguished within E. dermatitidis. One of these (B) contained prevalently strains from environmental sources, while the other (A) mainly comprised strains from clinical sources. This may be due to a difference in virulence. All strains from severe brain and disseminated infections in East Asia clustered in group A. However, strains of group A caused a relatively mild fungemia in patients outside East Asia. This revised version was published online in June 2006 with corrections to the Cover Date.     

PSEUDO-NITZSCHIA PUNGENS AND P. MULTISENES (BACILLARIOPHYCEAE): NUCLEAR RIBOSOMAL DNAS AND SPECIES DIFFERENCES1

The region of the nuclear ribosomal DNA (rDNA) operon containing the small subunit (SSU), internal transcribed spacer 1 (ITS1), and a portion of the 5.8s rDNA gene was sequenced in one isolate each of Pseudo-nitzschia multiseries (Hasle) Hasle and Pseudo-nitzschia pungens (Grunow in Cleve & Möller) Hasle. The SSUs of these two species were highly similar, differing only in 14 point mutations and one insertion/deletion in 1774 bp. The ITS1 sequences were more variable, with 57 point mutations and three insertion/deletions in 257 bp. There were no differences in 44 bp of the 5.8S sequences. Restriction fragment patterns (RFPs) for the restriction endonucleases HaeIII, Hha1, and Rsa1 for 13 isolates of P. multiseries from the Atlantic, Pacific, and Gulf coasts of the United States and 16 isolates of P. pungens from the three coasts of the United States, in addition to Japan and China, were compared. There were differences between the RFPs of P. multiseries and P. pungens that corresponded to sites mapped by the DNA sequences, but no infraspecific variation in RFPs was observed for either species. The differences in RFPs correlate with morphological, immunological, and other rDNA differences and support the recognition of these taxa as separate species.     

Morphology,ultrastructure and molecular phylogeny of cyst-producing Caladoa arcachonensis gen. et sp. nov. (Peridiniales,Dinophyceae) from France and Indonesia

The dinoflagellate order Peridiniales encompasses several well circumscribed families. However, the family level of some genera, such as Bysmatrum and Vulcanodinium, has remained elusive for many years. Four Peridinium-like strains were established from the Atlantic coast of France and North Sulawesi, Indonesia through cyst germination or isolation of single cells. The cyst-theca relationship was established on specimens from the French Atlantic. Their morphologies were examined using light, scanning and transmission electron microscopy. The cells were characterized by a much larger epitheca relative to the hypotheca, a large anterior sulcal (Sa) plate deeply intruding the epitheca and a small first anterior intercalary plate. The plate formula was identified as Po, cp, X, 4′, 3a, 7′′, 6C, 5S, 5′′′, 2′′′′, shared by Apocalathium, Chimonodinium, Fusiperidinium and Scrippsiella of the family Thoracosphaeraceae but the configuration of Sa plate and anterior intercalary plates is different. Transmission electron microscopy showed that the eyespot was located within a chloroplast comprising two rows of lipid globules and thus belongs to type A. All four strains were classified within a new genus Caladoa as C. arcachonensis gen. et sp. nov. Small subunit ribosomal DNA (SSU rDNA), partial large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer ribosomal DNA (ITS rDNA) sequences were obtained from all strains. Genetic distance based on ITS rDNA sequences between French and Indonesian strains reached 0.17, suggesting cryptic speciation in C. arcachonensis. The maximum likelihood and Bayesian inference analysis based on concatenated data from SSU and LSU rDNA sequences revealed that Caladoa is monophyletic and closest to Bysmatrum. Our results supported that Caladoa and Bysmatrum are members of the order Peridiniales but their family level remains to be determined. Our results also support that Vulcanodinium is closest to the family Peridiniaceae.     

Mitochondrial DNA polymorphism of the yeast <Emphasis Type="Italic">Saccharomyces bayanus</Emphasis> var. <Emphasis Type="Italic">uvarum</Emphasis>

Genetic relationships among forty-one strains of Saccharomyces bayanus var. uvarum isolated in different wine regions of Europe and four wild isolates were investigated by restriction analysis (RPLP) of mitochondrial DNA (mtDNA) with four restriction endonucleases, AluI, DdeI, HinfI and RsaI. No clear correlation between origin and source of isolation of S. bayanus var. uvarum strains and their mtDNA restriction profiles was found. On the whole, the mtDNA of S. bayanus var. uvarum is much less polymorphic than that of S. cerevisiae. This observation is in good agreement with results obtained by electrophoretic karyotyping. Unlike wine S. cerevisiae, strains of S. bayanus var. uvarum display a low level of chromosome length polymorphism.     

Taxon-specific oligonucleotide primers for detection of Glomus etunicatum

The 5.8S subunit and flanking internal transcribed spacer (ITS) regions in nuclear ribosomal DNA (rDNA) from spores of Glomus etunicatum MD107, MD127, TN101, and FL329 were amplified by polymerase chain reaction (PCR) using ITS1Kpn and ITS4Pst as primers. The amplification products (597, 599, 598, and 613 bp, respectively) were cloned and sequenced. The similarity among ITS region sequences from MD107, MD127, and TN101 was 99%, whereas the sequence similarity between the ITS regions of these three DNAs and that from FL329 was 91%. The 5.8S rDNA sequences of all four G. etunicatum isolates were identical. In contrast, major dissimilarities in the corresponding rDNA sequence regions of other glomalean taxa were observed. Oligonucleotide sequences unique to G. etunicatum were tested for their specificity in PCR amplification of genomic DNA from spores of 55 isolates comprising 29 glomalean fungi: 18 isolates of G. etunicatum, five G. intraradices, three G. claroideum, 16 other Glomus isolates, and 11 other glomalean taxa from each of four other genera. The G. etunicatum isolates were from a broad range of geographic regions and soils. The oligonucleotide pair GETU1:GETU2 primed specific amplification of an oligonucleotide sequence (approximately 400 bp) present in all G. etunicatum. This primer pair did not prime PCR when template consisted of DNA from any of the other glomalean fungi or any of the non-mycorrhizal controls, including roots of corn (Zea mays). In addition, the pair successfully detected G. etunicatum in nested PCR using a primary PCR product amplified from highly diluted extracts of colonized corn roots using modified ITS1:ITS4 primers. In the phylogenetic analysis of Glomus 5.8S and ITS2 rDNA region sequences, which included 500 bootstrap data sets, confidence in the G. etunicatum branch was very strong (90%) and clearly independent of G. claroideum and G. intraradices, to which it is very closely related. Accepted: 15 October 2000     

Serratia ficaria sp. nov., a bacterial species associated with Smyrna figs and the fig waspBlastophaga psenes

Fourteen strains isolated from figs, caprifigs, and fig wasps collected in California and Tunisia, and from a small black ant in France, constitute a new DNA hybridization group that is 25–56% related toSerratia species, and 6–17% related to other species of Enterobacteriaceae. This homogeneous group (90% relatedness within the group) constitutes a new species that is namedSerratia ficaria sp. nov. (type strain, ICPB 4050, ATCC 33105). Strains of this species have a characteristic odor, similar to that ofS: odorifera andPseudomonas perolens. No strain ofS. ficaria has yet been recovered from clinical specimens.     

Use of the 6-methylsalicylic-acid-synthase gene as a discriminating marker betweenaspergillus terreus andAspergillus flavipes

In nineteen pathogenic and saprophytic isolates denoted asAspergillus terreus the presence and restriction pattern of the genepksM (6-methylsalicylic acid synthase) was determined. Five patterns (A−E) were found and in three isolates the gene was missing. The RAPD (random amplified polymorphic DNA) patterns with three primers were analyzed. The strains withpksM pattern possibly derived from the most common pattern A by single mutation (patterns B−D) were also related by RAPD. Among them, three clades were found. The first one contained saprophytes from Asia, the other two clades contained both European and American pathogens and each of them one saprophyte. The sequences of rDNA region containing 5.8S rDNA and spacers ITS1 and ITS2 were established for representatives of each group and the strains missing thepksM gene. The isolates possessingpksM (although with different restriction patterns) grouped asA. terreus group, whereas the isolates lacking this gene were close toFennellia flavipes.     

Genetic reidentification of the pectinolytic yeast strain SCPP as Saccharomyces bayanus var. uvarum

Using genetic hybridization analysis, pulsed-field gel electrophoresis of chromosomal DNA and PCR/RFLP analysis of the MET2 gene, we reidentified 11 Champagne yeast strains. Two of them, SCPP and SC4, were found to belong to Saccharomyces bayanus var. uvarum and the remaining strains to S. cerevisiae. Strain SCPP (CLIB 2025) of S. bayanus var. uvarum is known as a producer of three pectinolytic enzymes. Received: 28 April 2000 / Received revision: 20 July 2000 / Accepted: 25 July 2000     

Cyst‐motile stage relationship and molecular phylogeny of a new freshwater dinoflagellate Gymnodinium plasticum from Plastic Lake,Canada

The dinophyceaen genus Gymnodinium was established with the freshwater species G. fuscum as type. According to Thessen et al. (2012), there are 268 species, with the majority marine species. In recently published molecular phylogenies based on ribosomal DNA sequences, Gymnodinium is polyphyletic. Here, a new freshwater Gymnodinium species, G. plasticum, is described from Plastic Lake, Ontario, Canada. Two strains were established by incubating single cysts, and their morphology was examined with light microscopy and scanning electron microscopy. The cyst had a rounded epicyst and hypocyst with a wide cingulum and smooth surface. Vegetative cells were characterized by an elongated nucleus running vertically and a deep sulcal intrusion. The apical structure complex was horseshoe‐shaped and consisted of two pronounced ridges with a deep internal groove, encircling 80% of the apex. Small subunit ribosomal DNA (SSU rDNA), large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer (ITS) sequences were obtained from cultured strains. Molecular phylogeny based on concatenated SSU, LSU and ITS sequences supports the monophyly of the Gymnodiniales sensu stricto clade but our results suggest that many Gymnodinium species might need reclassification. Gymnodinium plasticum is closest to Dissodinium pseudolunula in our phylogeny but distant from the type species G. fuscum, as are the other gymnodiniacean taxa.     

Differentiation of anaerobic polycentric fungi by rDNA PCR-RFLP

The suitability of restriction fragment length polymorphism (RFLP) analysis of the ribosomal DNA cluster for discriminating two genera of anaerobic polycentric fungi, Orpinomyces and Anaeromyces, was determined. Three PCR-amplified DNA fragments--nuclear small subunit (SSU; 18S rDNA), the nuclear large subunit (LSU; 28S rDNA) and internal transcribed spacer (ITS)--were restricted with endonucleases AluI, DraI, HinfI and MboI. Although the SSU DNA fragment could be restricted successfully by all four enzymes, no differences were observed between restriction patterns of Orpinomyces and Anaeromyces. The most polymorphic restriction pattern between Orpinomyces and Anaeromyces resulted from cleavage of LSU rDNA fragments cut by AluI and HinfI and ITS fragment cut by DraI and HinfI. Genus-specific RFLP patterns were determined for Orpinomyces and Anaeromyces genera; the results showed that the PCR-RFLP analysis of rDNA offers an easy and rapid tool for differentiation of two polycentric genera of anaerobic fungi, which could be hardly separated on the basis of morphology.     

New taxa refresh the phylogeny and classification of pleurostomatid ciliates (Ciliophora,Litostomatea)

A high diversity of pleurostomatid ciliates has been discovered in the last decade, and their systematics needs to be improved in the light of new findings concerning their morphology and molecular phylogeny. In this work, a new genus, Protolitonotus gen. n., and two new species, Protolitonotus magnus sp. n. and Protolitonotus longus sp. n., were studied. Furthermore, 19 novel nucleotide sequences of SSU rDNA, LSU rDNA and ITS1‐5.8S‐ITS2 were collected to determine the phylogenetic relationships and systematic positions of the pleurostomatid ciliates in this study. Based on both molecular and morphological data, the results demonstrated that: (i) as disclosed by the sequence analysis of SSU rDNA, LSU rDNA and ITS1‐5.8S‐ITS2, Protolitonotus gen. n. is sister to all other pleurostomatids and thus represents an independent lineage and a separate family, Protolitonotidae fam. n., which is defined by the presence of a semi‐suture formed by the right somatic kineties near the dorsal margin of the body; (ii) the families Litonotidae and Kentrophyllidae are both monophyletic based on both SSU rDNA and LSU rDNA sequences, whereas Amphileptidae are non‐monophyletic in trees inferred from SSU rDNA sequences; and (iii) the genera Loxophyllum and Kentrophyllum are both monophyletic, whereas Litonotus is non‐monophyletic based on SSU rDNA analyses. ITS1‐5.8S‐ITS2 sequence data were used for the phylogenetic analyses of pleurostomatids for the first time; however, species relationships were less well resolved than in the SSU rDNA and LSU rDNA trees. In addition, a major revision to the classification of the order Pleurostomatida is suggested and a key to its families and genera is provided.     

Molecular and morphological characterization of a poorly known marine ciliate, Myoschiston duplicatum precht 1935: implications for phylogenetic relationships between three morphologically similar genera -- Zoothamnium, Myoschiston, and Zoothamnopsis (Ciliophora, Peritrichia, Zoothamniidae)

We studied the morphology and molecular phylogeny of Myoschiston duplicatum, a peritrich ciliate that has been recorded as an epibiont of crustaceans, but which we also identified on marine algae from Korea. The important morphological characteristics revealed by silver staining of Myoschiston species have not been described because they are rarely collected. Using morphological methods, we redescribed the type species of the genus, Myoschiston duplicatum, and provided an improved diagnosis of Myoschiston. In addition, the coding regions for nuclear small subunit (SSU) rRNA and internal transcribed spacer 1‐5.8S‐internal transcribed spacer 2 sequences were sequenced. Phylogenetic analyses that included available SSU rDNA sequences of peritrichs from GenBank strongly supported a position of M. duplicatum within the family Zoothamniidae. In addition, phylogenetic analyses were performed with single datasets (ITS1‐5.8S‐ITS2) and combined datasets (SSU rDNA + ITS1‐5.8S‐ITS2) to explore further the phylogenetic relationship in the family Zoothamniidae between the three morphologically similar genera—Zoothamnium, Myoschiston, and Zoothamnopsis.     

Morpho-molecular diversity and phylogeny of Bysmatrum (Dinophyceae) from the South China Sea and France

The dinoflagellate genus Bysmatrum encompasses five epibenthic or tide-pool species and has been characterized by separated anterior intercalary plates. In the present study, we obtained six strains of Bysmatrum from the South China Sea and French Atlantic coast by isolating single cells/cysts from plankton and sediment samples. All strains were examined with light microscopy and scanning electron microscopy. Based on morphological observations, three strains were identified as Bysmatrum subsalsum, characterized by the elongated and rectangular first and a hexagonal second anterior intercalary plate. They differ from each other in the number of sulcal lists and the configuration of the first anterior intercalary plate. One strain was identified as Bysmatrum gregarium and the other two as Bysmatrum granulosum. The cyst-theca relationship of B. subsalsum from the French Atlantic was established by incubation of the cyst, and the geochemical composition of the cyst wall was measured through micro-Fourier transform infrared spectroscopy. Bysmatrum subsalsum from Malaysia shows a bright red stigma in the sulcal area under light microscopy, which was confirmed with transmission electron microscopy: it was identified as a type B eyespot. Small subunit ribosomal DNA (SSU rDNA), partial large subunit ribosomal DNA (LSU rDNA) and internal transcribed spacer (ITS) sequences were obtained from all six strains. The maximum likelihood and Bayesian inference analysis based on concatenated SSU, ITS and LSU sequences revealed that Bysmatrum is monophyletic and nested within Peridiniales. Our strains of B. subsalsum form a new ribotype in the molecular phylogeny (designated as ribotype B). The genetic distance based on ITS sequences among Bysmatrum species ranged from 0.34 to 0.47 and those genetic distances at the intraspecific level of B. subsalsum could reach 0.41, supporting the possibility of hidden crypticity within B. subsalsum.     

Taxonomy,ecology, and genetics of the yeast <Emphasis Type="Italic">Saccharomyces bayanus</Emphasis>: A new object for science and practice

The review considers various aspects of the biology of the yeast Saccharomyces bayanus, which is distantly related to the cultured yeast S. cerevisiae. The cryotolerant S. bayanus strains found in wine-making became the second most important yeast for basic and applied studies. Introduction of natural and experimental hybrids of S. cerevisiae × S. bayanus in a range of fermentation processes indicates the high breeding importance of S. bayanus. The biological species S. bayanus acts as a new gene pool for the scientific and breeding projects.     

Identification of species in the genus Pichia by restriction of the internal transcribed spacers (ITS1 and ITS2) and the 5.8S ribosomal DNA gene

In this study, the variability within the ribosomal DNA region spanning the internal transcribed spacers ITS1 and ITS2 and the 5.8S gene (5.8S-ITS rDNA) was used to differentiate species in the genus Pichia. The 5.8S-ITS rDNA region was PCR-amplified and the PCR product digested with the enzymes CfoI, HinfI, and HaeIII. The variability in the size of the amplified product and in the restriction patterns enabled differentiation between species in the genus Pichia, and between Pichia species and yeast species from other genera in the Yeast-id database (). Moreover, the restriction fragment length polymorphism (RFLP) patterns of the 5.8S-ITS enabled misidentified strains to be detected and revealed genetic heterogeneity between strains within the Pichia membranifaciens and Pichia nakazawae species. Ultimately, the RFLP patterns of the 5.8S-ITS rDNA failed to differentiate between some Pichia and Candida species that could be distinguished on the basis of the sequence of the 5.8S-ITS rRNA region or the sequence of the D1/D2 domain of the 26S rDNA gene.     

Lineage-specific variations of congruent evolution among DNA sequences from three genomes,and relaxed selective constraints on <Emphasis Type="Italic">rbc</Emphasis>L in <Emphasis Type="Italic">Cryptomonas</Emphasis> (Cryptophyceae)

Background  

Plastid-bearing cryptophytes like Cryptomonas contain four genomes in a cell, the nucleus, the nucleomorph, the plastid genome and the mitochondrial genome. Comparative phylogenetic analyses encompassing DNA sequences from three different genomes were performed on nineteen photosynthetic and four colorless Cryptomonas strains. Twenty-three rbc L genes and fourteen nuclear SSU rDNA sequences were newly sequenced to examine the impact of photosynthesis loss on codon usage in the rbc L genes, and to compare the rbc L gene phylogeny in terms of tree topology and evolutionary rates with phylogenies inferred from nuclear ribosomal DNA (concatenated SSU rDNA, ITS2 and partial LSU rDNA), and nucleomorph SSU rDNA.     

Construction and evaluation of self‐cloning bottom‐fermenting yeast with high SSU1 expression

Aim: To construct a self‐cloning brewer’s yeast that can minimize the unfavourable flavours caused by oxidation and certain kinds of sulfur compounds. Methods and Results: DNA fragments of a high‐expression promoter from the TDH3 gene originating from Saccharomyces cerevisiae were integrated into the promoter regions of the S. cerevisiae‐type and Saccharomyces bayanus‐type SSU1 genes of bottom‐fermenting brewer’s yeast. PCR and sequencing confirmed the TDH3 promoter was correctly introduced into the SSU1 regions of the constructed yeasts, and no foreign DNA sequences were found. Using the constructed yeasts, the concentration of sulfite in fermenting wort was higher when compared with the parent strain. In addition, the concentrations of hydrogen sulfide, 3‐methyl‐2‐buten‐1‐thiol (MBT) and 2‐mercapto‐3‐methyl‐1‐butanol (2M3MB) were lower when compared with the parent strain. Conclusion: We successfully constructed a self‐cloning brewer’s yeast with high SSU1 expression that enhanced the sulfite‐excreting ability and diminished the production ability of hydrogen sulfide, MBT and 2M3MB. Significance and Impact of the Study: The self‐cloning brewer’s yeast with high SSU1 expression would contribute to the production of superior quality beer with a high concentration of sulfite and low concentrations of hydrogen sulfide, MBT and 2M3MB.