Electrophoretic Karyotypes of Authentic Strains of the Sensu Stricto Group of the Genus Saccharomyces

Abstract

A comparative electrophoretic karyotyping study was performed with several certified authentic strains of the four species that could be distinguished by nuclear DNA (nDNA)-nDNA reassociation data within the sensu stricto group of the genus Succhuromyces. A multivariate analysis of the polymorphisms observed in pulsed-field gel electrophoretic profiles (numbers and molecular weights of separated units) revealed that the strains could be separated into four clusters that corresponded to the taxa that were distinguished on the basis of nDNA comparisons. Discrepancies between nDNA reassociation data and membership in the corresponding clusters were observed only with two strains of Succhuromycespurudoxus. Blind tests carried out with additional industrial strains confirmed the general validity of the statistical model created for comparison of karyotypes within the species included in Succharomyces sensu stricto.The species assigned by van der Walt (30) to the sensu stricto group of the genus Saccharomyces include the microorganisms that have been exploited industrially and scientifically by humans for the longest time. Innumerable ecological and technological investigations have redundantly demonstrated that Saccharomyces cerevisiae is the only species responsible for alcoholic fermentation of fruit juices (13). In addition, this species has long been the organism of choice for use as a model of the eukaryotic cell in biochemistry, physiology, genetics, and molecular biology (24).Genetic analysis has shown that the variable phenotypic expression of performance characteristics (including fermentation and assimilation) often observed in Saccharomyces strains may result from the presence of multiple gene loci that can be active, silent, or missing in different strains of the same species (6, 8,10,17,19). This may explain why definite identification of an unknown isolate as S. cerevisiae by conventional taxonomy is often difficult. In addition, these yeasts, which have been domesticated as a result of millennia of exploitation in human-created, industrial environments, are often homothallic or aneuploid and therefore are very difficult to use as models for genetic study and strain improvement.Over the years the variability in the physiological performance of yeasts has resulted in a fluctuating classification. The 20 different species accepted at the beginning of this century were in 1970 reduced to 8 species by van der Walt (30), who described 13 new taxa and coined the term Saccharomyces sensu stricto. In 1984 Yarrow (38) combined the 21 species described by van der Walt in 1970 into one species because he found that the organisms were ecologically, physiologically, and technologically identical.A series of subsequent nuclear DNA (nDNA)-nDNA reassociation studies revealed that the 21 previously described taxa belonging to the sensu stricto group, which made up the species S. cerevzsiae sensu Yarrow (38), included at least the following four variably related species: Saccharomyces bayanus, S. cerevisiae, Saccharomyce...

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

“…This classification was further substantiated by many other studies on electrophoretic karyotypes (2,8,18,38), mitochondria1 DNA (mtDNA) restriction endonuclease profiles (9, rDNA restriction analysis (1 2), analysis of randomly amplified polymorphic DNAs (RAPDs) (1 3), and by studies which showed that interspecific hybrids between these species, although viable, gave abortive ascospores (14). Most of these studies were intended to identify the four different species and to classify different wild or industrial strains of Saccharomyces.…”

Karyotypes of Saccharomyces sensu lato species

“…Yeasts belonging to the genus Saccharomyces can be divided into the sensu strict0 and sensu lato groups. The sibling species of the Saccharomyces cerevisiae complex have been shown to exhibit uniform karyotypes (Cardinali & Martini, 1994;Carle & Olson, 1985;Naumov et al, 1992Naumov et al, , 1995Vaughan-Martini et al, 1993). Their chromosomes have been divided into three different classes on the basis of their size: light (< 500 kb), medium (500-1000 kb) and heavy (> 1000 kb) (Vaughan-Martini et al, 1993).…”

Genomic Exploration of the Hemiascomycetous Yeasts: 5. Saccharomyces bayanus var. uvarum

“…bayanus/uvarum hybrids [7], and genuine S. cerevisiae subtelomeric sequences, found in S. paradoxus, are absent from the genome of strain CBS 7001 [8]. The heterogeneity among S. bayanus strains is re£ected by their variable number of chromosomes, ranging from 14 to 17 [9], whereas the number of chromosomes remains stable at 16 in the uvarum sub-group. The chromosome structure of CBS 7001 has been investigated and compared to S. cerevisiae chromosomes: several translocations were described [10] between chromosomes II and IV, VIII and XV.…”