Ann Vaughan-Martini

Saccharomyces Meyen ex Reess

Publisher Summary This chapter focuses on Saccharomyces genus and its member species. The cells of this genus are globose, ellipsoidal, or cylindroidal. Vegetative reproduction occurs through multilateral budding, and pseudohyphae may be formed but not septate hyphae. The vegetative phase is predominantly diploid (or of higher ploidy) and conjugation occurs on or soon after germination of the ascospores. The ascospores are globose to short ellipsoidal, with a smooth wall and usually one to four per ascus. The member species of this genus include Saccharomyces barnettii, Saccharomyces bayanus, Saccharomyces castellii, Saccharomyces cerevisiae, and Saccharomyces dairenensis. The cells of Saccharomyces barnettii species, after a growth in 5% malt extract at 25° C for three days appear as globose, ovoidal, or elongate. The vegetative cells of this species are transformed directly into persistent asci containing one or two, and rarely four, globose to short ellipsoidal ascospores. The ascospores were observed on acetate agar usually after 20-40 days at 25° C. The cells of Saccharomyces bayanus species, after growth in 5% malt extract for 3 days at 25° C, are globose, ovoidal, or elongate and are usually isolated. The vegetative cells are transformed directly into persistent asci containing one to four globose to short ellipsoidal ascospores.

Facts, myths and legends on the prime industrial microorganism

SummaryArchaic speculations and firmly established legends regarding the origin of the yeastSaccharomyces cerevisiae and related species are revisited in light of past and recent ecological evidence pointing to a strict association with artificial, man-made environments such as wineries and fermentation plants. The nomenclature within this industrially important group is also discussed in view of the modifications imposed from application of molecular techniques to classification.

Electrophoretic karyotyping as a taxonomic tool in the genus Saccharomyces

SummaryThe electrophoretic karyotypes of strains of the ten species of the yeast genusSaccharomyces (sensu Vaughan-Martini & Martini 1992) were determined by the CHEF (contour-clamped homogeneous electric field) system of pulsed field gel electrophoresis. The number of bands was found to vary from 6 to 17 and the calculated molecular weights of haploid genomes ranged from 7.9 to 14.6 Mbp. The type strains ofS. exiguus and the four species of theSaccharomyces sensu stricto complex (S. bayanus, S. cerevisiae, S. paradoxus andS. pastorianus) have genomes comprised of chromosomes of all three size classes: light (< 500 kb), medium (500–1000 kb) and heavy (> 1,000 kb).Saccharomyces kluyveri DNA has only heavy bands, while the remaining species exhibit medium and heavy chromosomes. When more than one strain of each species was examined, it was seen that while the speciesS. bayanus, S. castellii, S. cerevisiae, S. kluyveri, S. paradoxus andS. pastorianus showed uniform karyotypes,S. dairensis, S. exiguus, S. servazzii andS. unisporus comprise heterogeneous taxa.

A Taxonomic Key for the Genus Saccharomyces

Summary Complete physiological analyses of eighty-six strains of the ten recognized species of the genus Saccharomyces were performed with the scope of establishing a reliable taxonomic key. Results showed that it is possible to clearly distinguish strains of the species Sacch. bayanus, Sacch. cerevisiae, Sacch. kluyveri, Sacch. paradoxus, Sacch. pastorianus, Sacch. servazzii and Sacch. unisporus . Some difficulties can be encountered in the classification of strains of Sacch. dairensis and Sacch. exiguus which probably comprise heterogeneous taxa.

Saccharomyces Meyen ex Reess (1870)

Publisher Summary This chapter studies the genus Saccharomyces. In the determination of the asexual reproduction it is seen that budding is multilateral and cells are globose, ellipsoid, or cylindroid. Pseudohyphae may be formed, but septate hyphae are absent. In sexual reproduction it is found that the asexual state may be haploid but is often diploid or of higher ploidy. Conjugation may occur between complementary mating types, or, more commonly, diploid cells convert directly into asci. Ascospores are globose to short ellipsoid, with a smooth wall, and there are usually one to four per ascus. Asci are persistent. The chapter also discusses physiology/biochemistry and phylogenetic placement of the genus in which fermentation is normally vigorous, starch-like compounds are not produced, and no growth occurs with nitrate as a sole source of nitrogen. The major ubiquinone is CoQ-6 and the diazonium blue B reaction is negative. The type species taken is Saccharomyces cerevisiae. Five of the currently accepted species of Saccharomyces (S. aboricolus, S. cariocanus, S. mikatae, S. kudriavzevii, and S. paradoxus) are found in natural environments.

Determination of ethanol production

Publisher Summary This chapter presents a simple method that allows a rough evaluation of ethanol yields from the gravimetric estimation of the CO2 formed in a liquid fermentation medium containing an excess of glucose (24% w/v). The test is carried out at 25° C in Erlenmeyer flasks plugged with a special glass device (Muller valve) that causes the CO2 produced by fermentation to pass through concentrated sulfuric acid. This acts as a water trap to eliminate weight loss as water vapor. In this method, cells from a 24 hour preculture grown with agitation (150 rpm) at 25° C are centrifuged, washed twice, and then resuspended in sterile, deionized water. Flasks are weighed daily until values are stationary and relative ethanol production (as volume percent) is calculated by multiplying the weight loss (as grams of CO2) by 1.25. More reliable results can be obtained with a synthetic medium, which include 13.7 g/l Bacto Yeast Nitrogen Base and glucose 24% (w/v), whose pH is adjusted to 3.0. Sterilization is preferably done by Tyndalization, which involves the exposure of the medium to steam on three consecutive days. The medium is steamed for 30 minutes on the first day, incubated at room temperature overnight, steamed for a further 30 minutes on the second day, reincubated and steamed again for 30 minutes on the third day. The first days exposure kills non-spore-forming organisms, subsequent incubation allows the germination of bacterial endospores, which are then killed during the second or third steaming.

In vitro antimycotic activity of a Williopsis saturnus killer protein against food spoilage yeasts

The in vitro antimycotic activity of a purified killer protein (KT4561) secreted by a strain of Williopsis saturnus was tested against 310 yeast strains belonging to 21 food spoilage species of 14 genera (Candida, Debaryomyces, Dekkera, Hanseniaspora, Issatchenkia, Kazachstania, Kluyveromyces, Pichia, Rhodotorula, Saccharomyces, Schizosaccharomyces, Torulaspora, Yarrowia and Zygosaccharomyces). Minimum inhibitory concentration (MIC) determinations showed that over 65% of the target strains were susceptible to concentrations < or = 32 microg/ml of KT4561. Three conventional food-grade antimicrobial agents were used as controls: 41, 33 and 40% of the target strains were sensitive to < or = 512 mg/ml of ethyl 3-hydroxybenzoate (E214), potassium sorbate (E202) or potassium metabisulphite (E224), respectively. The susceptibility of food spoilage yeasts towards KT4561, E214, E202 and E224 was species- and strain-dependent. In most cases KT4561 exhibited MIC values several orders of magnitude lower (100 to 100,000 times) than those observed for E214, E202 and E224. With only a few exceptions, the activity of KT4561 was pH-, ethanol-, glucose- and NaCl-independent. The present study demonstrates the potential of this yeast killer protein as a novel and natural control agent against food spoilage yeasts.

Differential killer sensitivity as a tool for fingerprinting wine-yeast strains of Saccharomyces cerevisiae

The extreme variability of the killer phenomenon in nature, expressed differently in different strains of the same yeast species, embodies an exceptional potential for the discrimination of yeasts at the strain level. Killer-sensitive relationships between a killer reference panel of 24 yeasts belonging to 13 species of six genera, and different industrial wine-starters ofSaccharomyces cerevisiae can be used profitably for a rapid and simple fingerprinting procedure.

Saccharomyces barnetti and Saccharomyces spencerorum : two new species of Saccharomyces sensu lato (van der Walt)

In the course of a study of DNA base sequence homology, 19 strains labelled asSaccharomyces exiguus, its imperfect state,Candida holmii, orC. milleri were examined. Results confirmed the separation ofC. milleri as a separate species. The remaining strains can be divided into three distinct groups of genomic relatedness. The type cultures ofS. exiguus andC. holmii form a cluster with 10 other strains showing variable reassociation values ranging from 100 to 40%. The remaining four strains comprise two separate species showing no nucleotide relatedness between themselves nor to either theS. exiguus complex or toC. milleri. Physiological analyses demonstrate that it is possible to separate these four taxa on the basis of a few simple tests. The two new species are described respectively asSaccharomyces barnetti honoring James Barnett in recognition of his invaluable work in the field of yeast taxonomy andSaccharomyces spencerorum in honor of J.F.T. and Dorothy M. Spencer who have made innumerable contributions to the genetics and biotechnological application of yeasts.

Kazachstania bromeliacearum sp. nov., a yeast species from water tanks of bromeliads

Cultures of a novel nutritionally specialized, fermentative yeast species were isolated from 34 water tanks of five bromeliad species, two mangrove sediment samples and one swamp water sample in Rio de Janeiro, Brazil. Sequence analysis of the D1/D2 domains of the large subunit of the rRNA gene showed that the novel species belongs to the genus Kazachstania. The novel species differs from Kazachstania martiniae by 11 substitutions and 2 gaps in the sequence of the domains D1/D2 of the LSU rRNA gene. The name Kazachstania bromeliacearum sp. nov. is proposed for the novel species. The type strain is IMUFRJ 51496T (=CBS 7996T=DBVPG 6864T=UFMG BR-174T).