Gennadi I. Naumov

Three new species in the Saccharomyces sensu stricto complex: Saccharomyces cariocanus, Saccharomyces kudriavzevii and Saccharomyces mikatae

On the basis of genetic analysis, molecular karyotyping and sequence analyses of the 18S rRNA and internal transcribed spacer (ITS) region, three new Saccharomyces species are described, Saccharomyces cariocanus (with type strain NCYC 2890T), Saccharomyces kudriavzevii (with type strain NCYC 2889T) and Saccharomyces mikatae (with type strain NCYC 2888T). Genetic and molecular analyses did not confirm the previously observed conspecificity of Saccharomyces paradoxus and S. cariocanus. The latter species exhibits postzygotic isolation from representative strains from all known geographical populations of S. paradoxus: European, Far-East Asian, North American and Hawaiian.

Saccharomyces paradoxus and Saccharomyces cerevisiae are associated with exudates of North American oaks

Genetic hybridization and karyotypic analyses revealed the biological species Saccharomyces paradoxus and Saccharomyces cerevisiae in exudates from North American oaks for the first time. In addition, two strains collected from elm flux and from Drosophila by Phaff in 1961 and 1952 were reidentified as S. paradoxus. Each strain studied showed a unique profile of chromosomal hybridization with a probe for the retrotransposable element Ty1. The wild distribution of natural Saccharomyces sensu stricto yeasts is discussed.

Association of Saccharomyces bayanus var. uvarum with some French wines: genetic analysis of yeast populations

Using genetic hybridization analysis, electrophoretic karyotyping and PCR-RFLP of the MET2 gene, we found that the yeast Saccharomyces bayanus var. uvarum is associated with certain types of wines produced in the Val de Loire, Sauternes, and Jurancon regions. The average frequency of appearance of this yeast in the three regions of France was 41, 7 and 77%, respectively. In contrast, we did not find S. bayanus var. uvarum in red wines produced in the Bordeaux area. The results of this study, as well as the findings already reported on Tokay (Slovakia), Muscat (Crimea, Ukraine) and Amarone (Italy) wines, lead us to consider that distribution of S. bayanus var. uvarum yeast is connected with low temperature climatic conditions and/or wine technologies in which must fermentation is at least partially carried out at low temperatures (10-15 degrees C).

Molecular genetic study of introgression between Saccharomyces bayanus and S. cerevisiae

The genomic constitution of different S. bayanus strains and natural interspecific Saccharomyces hybrids has been studied by genetic and molecular methods. Unlike S. bayanus var. uvarum, some S. bayanus var. bayanus strains (the type culture CBS 380, CBS 378, CBS 425, CBS 1548) harbour a number of S. cerevisiae subtelomeric sequences: Y′, pEL50, SUC, RTM and MAL. The two varieties, having 86–100% nDNA–nDNA reassociation, are partly genetically isolated from one another but completely isolated from S. cerevisiae. Genetic and molecular data support the maintaining of var. bayanus and var. uvarum strains in the species S. bayanus. Using Southern hybridization with species‐specific molecular markers, RFLP of the MET2 gene and flow cytometry analysis, we showed that the non‐S. cerevisiae parents are different in lager brewing yeasts and in wine hybrid strains. Our results suggest that S. pastorianus is a hybrid between S. cerevisiae and S. bayanus var. bayanus, while S. bayanus var. uvarum contributed to the formation of the wine hybrids S6U and CID1. According to the partial sequence of ACT1 gene and flow cytometry analysis, strain CID1 is a triple hybrid between S. cerevisiae, S. kudriavzevii and S. bayanus var. uvarum. Copyright

Genetic and karyotypic identification of wine Saccharomyces bayanus yeasts isolated in France and Italy

Summary Using genetic analysis and electrophoretic karyotyping, we have reidentified 21 wine strains belonging to the genus Saccharomyces , isolated in regions of traditional wine making and able to ferment melibiose. Our results show that 19 strains belong to the biological species Saccharomyces bayanus (ex S. uvarum ) and 2 to the biological species S. cerevisiae .

Genetic identification of naturalSaccharomyces sensu stricto yeasts from Finland, Holland and Slovakia

Genetic and karyotypic studies of naturalSaccharomyces sensu stricto yeasts from Finland, Holland and Slovakia revealed three wild sibling-species:Saccharomyces cerevisiae, Saccaromyces bayanus andSaccharomyces paradoxus.

Molecular genetic identification of Saccharomyces sensu stricto strains from African sorghum beer

Genetic relationships of 24 phenotypically different strains isolated from sorghum beer in West Africa and the type cultures of the Saccharomyces sensu stricto species were investigated by universally primed polymerase chain reaction (PCR) analysis, microsatellite fingerprinting and PCR-restriction fragment length polymorphism (RFLP) of the ribosomal internal transcribed spacers. The results demonstrate that internal transcribed spacer (ITS) PCR-RFLP analysis with the endonucleases HaeIII, HpaII, ScrFI and TaqI is useful for discriminating S. cerevisiae, S. kudriavzevii, S. mikatae from one another and from the S. bayanus/S. pastorianus and S. cariocanus/S. paradoxus pairs. The sorghum beer strains exhibited the same restriction patterns as the type culture of S. cerevisiae CBS 1171. PCR profiles generated with the microsatellite primer (GTG)(5) and the universal primer N21 were almost identical for all isolates and strain CBS 1171. Despite phenotypic peculiarities, the strains involved in sorghum beer production in Ghana and Burkina Faso belong to S. cerevisiae. However, based on sequencing of the rDNA ITS1 region and Southern hybridisation analysis, these strains represent a divergent population of S. cerevisiae.

Natural polyploidization of some cultured yeast Saccharomyces sensu stricto: Auto- and allotetraploidy

Using genetic and flow cytometric analyses, we showed that wine strain S6U is an allotetraploid of S. cerevisiae x S. bayanus. Hybrid constitution of the strain and its meiotic segregants was confirmed by Southern hybridization analysis of their chromosomal DNAs using four S. cerevisiae cloned genes: LYS2 (chr. II), TRK1 (chr. X), ARG4 (chr. VIII), ACT1 (chr. VI) and PCR/RFLP analysis of the MET2 gene (chr. XIV). Monosporic progeny of strain S6U was highly viable in first generation but completely nonviable in the second one. According to the genetic analysis, sherry strain S. cerevisiae SBY 2592 was found to be an autotetraploid heterozygous for homo-heterothallism.

Differentiation of European and Far East Asian populations of Saccharomyces paradoxus by allozyme analysis

Allozyme electrophoresis was used to characterize 39 isolates belonging to the wild yeast species Saccharomyces paradoxus for variation at nine enzyme loci. The data revealed significant genetic differentiation between isolates from two geographically distinct regions, one including continental Europe and the other including the Russian Far East and Japan. The results are consistent with previous observations indicating that there is partial reproductive isolation between isolates collected from these regions, and they suggest the possibility that these two populations represent an early stage in speciation.

A new genetically isolated population of the Saccharomyces sensu stricto complex from Brazil

Genetic and karyotypic studies of someSaccharomyces sensu stricto yeasts from Brazil revealed a genetically isolated population which apparently represents a new sibling species ofS. cerevisiae.