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Malcolm Stratford - One of the best experts on this subject based on the ideXlab platform.
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species specific pcr primers for the rapid identification of yeasts of the genus Zygosaccharomyces
Fems Yeast Research, 2011Co-Authors: Elizabeth Harrison, Malcolm Stratford, Alastair Muir, Alan E. WhealsAbstract:Species-specific primer pairs that produce a single band of known product size have been developed for members of the Zygosaccharomyces clade including Zygosaccharomyces bailii, Zygosaccharomyces bisporus, Zygosaccharomyces kombuchaensis, Zygosaccharomyces lentus, Zygosaccharomyces machadoi, Zygosaccharomyces mellis and Zygosaccharomyces rouxii. An existing primer pair for the provisional new species Zygosaccharomyces pseudorouxii has been confirmed as specific. The HIS3 gene, encoding imidazole-glycerolphosphate dehydratase, was used as the target gene. This housekeeping gene evolves slowly and is thus well conserved among different isolates, but shows a significant number of base pair changes between even closely related species, sufficient for species-specific primer design. The primers were tested on type and wild strains of the genus Zygosaccharomyces and on members of the Saccharomycetaceae. Sequencing of the D1/D2 region of rDNA was used to confirm the identification of all nonculture collection isolates. This approach used extracted genomic DNA, but in practice, it can be used efficiently with a rapid colony PCR protocol. The method also successfully detected known and new hybrid strains of Z. rouxii and Z. pseudorouxii. The method is rapid, robust and inexpensive. It requires little expertise by the user and is thus useful for preliminary, large-scale screens.
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Species‐specific PCR primers for the rapid identification of yeasts of the genus Zygosaccharomyces
FEMS yeast research, 2011Co-Authors: Elizabeth Harrison, Malcolm Stratford, Alastair Muir, Alan E. WhealsAbstract:Species-specific primer pairs that produce a single band of known product size have been developed for members of the Zygosaccharomyces clade including Zygosaccharomyces bailii, Zygosaccharomyces bisporus, Zygosaccharomyces kombuchaensis, Zygosaccharomyces lentus, Zygosaccharomyces machadoi, Zygosaccharomyces mellis and Zygosaccharomyces rouxii. An existing primer pair for the provisional new species Zygosaccharomyces pseudorouxii has been confirmed as specific. The HIS3 gene, encoding imidazole-glycerolphosphate dehydratase, was used as the target gene. This housekeeping gene evolves slowly and is thus well conserved among different isolates, but shows a significant number of base pair changes between even closely related species, sufficient for species-specific primer design. The primers were tested on type and wild strains of the genus Zygosaccharomyces and on members of the Saccharomycetaceae. Sequencing of the D1/D2 region of rDNA was used to confirm the identification of all nonculture collection isolates. This approach used extracted genomic DNA, but in practice, it can be used efficiently with a rapid colony PCR protocol. The method also successfully detected known and new hybrid strains of Z. rouxii and Z. pseudorouxii. The method is rapid, robust and inexpensive. It requires little expertise by the user and is thus useful for preliminary, large-scale screens.
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Zygosaccharomyces Barker (1901)
The Yeasts, 2011Co-Authors: Stephen A. James, Malcolm StratfordAbstract:Publisher Summary This chapter studies the genus Zygosaccharomyces. In the determination of the asexual reproduction it is seen that cell division is by multilateral budding on a narrow base. Cells are spherical, ovoid, or elongate. Pseudohyphae, if formed, are generally not well differentiated, and true hyphae are not produced. In sexual reproduction it is found that the asci are persistent and are generally formed by conjugation, either between a cell and its bud or, more frequently, between independent cells, often with both cells producing ascospores, thus giving rise to a dumbbell-shaped ascus. Ascospores are smooth and globose to ellipsoidal, and there are one to four per ascus. The chapter also discusses physiology/biochemistry and phylogenetic placement of the genus in which glucose is fermented, but not galactose. Nitrate is not assimilated and pellicles are not formed on liquid medium. Coenzyme Q-6 is produced and diazonium blue B reaction is negative. The type species taken is Zygosaccharomyces rouxii. The taxonomic re-evaluation followed extensive work by Winge and Lindegren and their collaborators, who reported that no clear distinction could be made between the Saccharomyces, Torulaspora, or Zygosaccharomyces. The genus currently comprises just six species, but this number is likely to increase in the future as the accuracy of yeast identification continues to improve through the use of DNA-based methods such as ribosomal RNA gene sequencing. With regard to Zygosaccharomyces, rRNA gene sequencing has already proved invaluable, both for differentiating between physiologically similar species and for identifying new species and Z. lentus.
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physiological characterization of spoilage strains of Zygosaccharomyces bailii and Zygosaccharomyces rouxii isolated from high sugar environments
International Journal of Food Microbiology, 2007Co-Authors: Patricia Martorell, Hazel Steels, Malcolm Stratford, Ma Teresa Fernandezespinar, Amparo QuerolAbstract:Two isolates of spoilage yeasts Zygosaccharomyces bailii and Zygosaccharomyces rouxii were obtained from a high sugar environment, in a factory producing candied fruit and nougat. Other strains, Z. bailii from other environments and other isolates from high sugar/salt environments were obtained for comparison (Zygosaccharomyces lentus, Candida magnoliae, Candida halophila and Pichia guilliermondii). A full physiological assessment of these isolates was carried out, of preservative and biocide resistance, osmotolerance, ethanol-tolerance, low pH resistance, degree of fermentation, and growth temperature and survival to pasteurisation. Results showed that the strains isolated from high sugar environments did not show extreme physiology. These were robust strains but within the normal parameters expected for the species. One exception to this was that the Z. bailii strains were abnormally able to grow at 37 degrees C. In all strains other than C. magnolia and C. halophila, cells were able to adapt to high levels of sugar. Cultures grown in high glucose concentrations were subsequently able to tolerate higher concentrations of glucose than previously. Similarly, high sugar was found to confer a degree of protection against pasteurisation, enabling survival in what would have otherwise been a lethal treatment. Isolates of Z. bailii showed a high level of resistance to preservatives such as sorbic acid, benzoic acid, acetic acid, cinnamic acid, and ethanol, and also to heat. Unexpectedly Z. bailii isolates were not exceptionally resistant to biocides such as peracetic acid, or hypochlorite. These results indicate that spoilage by yeasts such as Z. bailii may be better prevented by use of biocidal cleaning agents in the factory, rather than treating the food with preservatives.
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Physiological characterization of spoilage strains of Zygosaccharomyces bailii and Zygosaccharomyces rouxii isolated from high sugar environments.
International Journal of Food Microbiology, 2007Co-Authors: Patricia Martorell, Hazel Steels, Malcolm Stratford, Ma Teresa Fernández-espinar, Amparo QuerolAbstract:Abstract Two isolates of spoilage yeasts Zygosaccharomyces bailii and Zygosaccharomyces rouxii were obtained from a high sugar environment, in a factory producing candied fruit and nougat. Other strains, Z. bailii from other environments and other isolates from high sugar/salt environments were obtained for comparison (Zygosaccharomyces lentus, Candida magnoliae, Candida halophila and Pichia guilliermondii). A full physiological assessment of these isolates was carried out, of preservative and biocide resistance, osmotolerance, ethanol-tolerance, low pH resistance, degree of fermentation, and growth temperature and survival to pasteurisation. Results showed that the strains isolated from high sugar environments did not show extreme physiology. These were robust strains but within the normal parameters expected for the species. One exception to this was that the Z. bailii strains were abnormally able to grow at 37 °C. In all strains other than C. magnolia and C. halophila, cells were able to adapt to high levels of sugar. Cultures grown in high glucose concentrations were subsequently able to tolerate higher concentrations of glucose than previously. Similarly, high sugar was found to confer a degree of protection against pasteurisation, enabling survival in what would have otherwise been a lethal treatment. Isolates of Z. bailii showed a high level of resistance to preservatives such as sorbic acid, benzoic acid, acetic acid, cinnamic acid, and ethanol, and also to heat. Unexpectedly Z. bailii isolates were not exceptionally resistant to biocides such as peracetic acid, or hypochlorite. These results indicate that spoilage by yeasts such as Z. bailii may be better prevented by use of biocidal cleaning agents in the factory, rather than treating the food with preservatives.
Lisa Solieri - One of the best experts on this subject based on the ideXlab platform.
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Draft Genome Sequences of the Highly Halotolerant Strain Zygosaccharomyces rouxii ATCC 42981 and the Novel Allodiploid Strain Zygosaccharomyces sapae ATB301T Obtained Using the MinION Platform.
Microbiology resource announcements, 2018Co-Authors: Melissa Bizzarri, Stefano Cassanelli, Leszek P. Pryszcz, Jan Gawor, Robert Gromadka, Lisa SolieriAbstract:ABSTRACT Here, we report draft genome sequences of the halotolerant and allodiploid strains Zygosaccharomyces rouxii ATCC 42981 and Zygosaccharomyces sapae ABT301T. Illumina and Oxford Nanopore MinION sequencing revealed genome sizes of 20.9 and 24.7 Mb, respectively. This information will be useful for deciphering the genetics of hybrid adaptation to high salt and sugar concentrations in nonconventional yeasts.
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Fermentative aptitude of non-Saccharomyces wine yeast for reduction in the ethanol content in wine
European Food Research and Technology, 2014Co-Authors: Mirko Gobbi, Lisa Solieri, Paolo Giudici, Luciana Vero, Francesca Comitini, Lucia Oro, Maurizio CianiAbstract:Over the last few decades, there has been a progressive increase in the ethanol content in wines due to global climate change and to the new wine styles that are associated with increased grape maturity. This increased ethanol content can have negative consequences on the sensory properties of the wines, human health, and economic aspects. Several microbiological approaches for decreasing the ethanol content have been suggested, such as strategies based on genetically modified yeasts, the adaptive evolution of yeasts, and the use of non- Saccharomyces yeast. In the present study, we investigated the interspecies and intraspecies variability of some non- Saccharomyces wine yeast species under anaerobic fermentation conditions. Across different grape juices and fermentation trials, Hanseniaspora uvarum , Zygosaccharomyces sapae , Zygosaccharomyces bailii, and Zygosaccharomyces bisporus promoted significant reductions in ethanol yield and fermentation efficiency in comparison with Saccharomyces cerevisiae . The diversion of alcoholic fermentation and the abundant formation of secondary compounds might explain the marked reduction in ethanol yield, as determined through the segregation of the majority of the strains according to their species attributes observed using principal component analysis. These data suggest that careful evaluation of interspecies and intraspecies biodiversity can be carried out to select yeast that produces low-ethanol yields.
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Quantitative phenotypic analysis of multistress response in Zygosaccharomyces rouxii complex
FEMS yeast research, 2014Co-Authors: Lisa Solieri, Tikam Chand Dakal, Silvio BicciatoAbstract:Zygosaccharomyces rouxii complex comprises three yeasts clusters sourced from sugar- and salt-rich environments: haploid Zygosaccharomyces rouxii, diploid Zygosaccharomyces sapae and allodiploid/aneuploid strains of uncertain taxo- nomic affiliations. These yeasts have been characterized with respect to gene copy number variation, karyotype variability and change in ploidy, but func- tional diversity in stress responses has not been explored yet. Here, we quanti- tatively analysed the stress response variation in seven strains of the Z. rouxii complex by modelling growth variables via model and model-free fitting meth- ods. Based on the spline fit as most reliable modelling method, we resolved dif- ferent interstrain responses to 15 environmental perturbations. Compared with Z. rouxii CBS 732 T and Z. sapae strains ABT301 T and ABT601, allodiploid strain ATCC 42981 and aneuploid strains CBS 4837 and CBS 4838 displayed higher multistress resistance and better performance in glycerol respiration even in the presence of copper. l-based logarithmic phenotypic index high- lighted that ABT601 is a slow-growing strain insensitive to stress, whereas ABT301 T grows fast on rich medium and is sensitive to suboptimal conditions. Overall, the differences in stress response could imply different adaptation mechanisms to sugar- and salt-rich niches. The obtained phenotypic profiling contributes to provide quantitative insights for elucidating the adaptive mecha- nisms to stress in halo- and osmo-tolerant Zygosaccharomyces yeasts.
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Unravelling genomic diversity of Zygosaccharomyces rouxii complex with a link to its life cycle
FEMS yeast research, 2013Co-Authors: Lisa Solieri, Tikam Chand Dakal, Maria Antonietta Croce, Paolo GiudiciAbstract:Zygosaccharomyces rouxii and the related species Zygosaccharomyces sapae (hereafter referred to as Z. rouxii complex) are protoploid hemiascomycete yeasts relevant in the elaboration and spoilage of foodstuff. Divergence of Z. rouxii complex before whole genome duplication, leading to the genus Saccharomyces, makes these yeasts very attractive for genome evolution study. Relatively little is known, however, about the diversity in this branch at the genetic and physiological levels. In this work, we investigated Z. rouxii complex, encompassing strains that in other works have been studied separately and comparing them in a comprehensive way. We showed that the majority of strains are unusually heterogeneous in their ribosomal DNA, a signal of relaxation of concerted evolution. Further analysis showed that they have hypervariable karyotypes, different levels of ploidy, and that housekeeping markers vary both in copy number and sequence. Overall, the results provide compelling evidence that the strains considered in this study are a complex of haploid, aneuploid and diploid mosaic lineages. The reproductive mode and life cycle of Zygosaccharomyces could lead to this unsuspected diversity.
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Zygosaccharomyces sapae sp. nov., isolated from Italian traditional balsamic vinegar.
International Journal of Systematic and Evolutionary Microbiology, 2012Co-Authors: Lisa Solieri, Tikam Chand Dakal, Paolo GiudiciAbstract:Fourteen yeast isolates were recovered from two traditional balsamic vinegar (TBV) samples collected in the provinces of Modena and Reggio Emilia, Italy. Microsatellite-primed-PCR (MSP-PCR) was used to de-replicate the isolate collection into two representative strains, ABT301T and ABT601. Phylogenetic analysis based on the D1/D2 domains of the 26S rRNA gene indicated that these strains represented a distinct species of the genus Zygosaccharomyces, closely related to Zygosaccharomyces rouxii and Zygosaccharomyces mellis. Physiological and morphological tests supported the recognition of a novel taxon of halotolerant, osmotolerant, non-psychrotolerant and maltose-fermentation-negative yeasts showing a chain or star-shaped pattern of budding cells, which remained attached to each other. Morphological observations offered evidence of ascospore formation. A novel species, Zygosaccharomyces sapae sp. nov., is proposed to accommodate these strains, with strain ABT301T ( = CBS 12607T = MUCL 54092T) as the type strain. Based on D1/D2 domain phylogenetic analysis, the novel strains shared the highest sequence similarity (100 %) with Zygosaccharomyces sp. strain NCYC 3042, previously isolated from sugar [James, S. A., Bond, C. J., Stratford, M. & Roberts, I. N. (2005). FEMS Yeast Res 5, 747–755]. However, based on phylogenetic (internal transcribed spacers, ITS), PCR fingerprinting and physiological analyses, marked differences were observed between the novel species and strain NCYC 3042, and these results are discussed in more detail.
Paolo Giudici - One of the best experts on this subject based on the ideXlab platform.
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Fermentative aptitude of non-Saccharomyces wine yeast for reduction in the ethanol content in wine
European Food Research and Technology, 2014Co-Authors: Mirko Gobbi, Lisa Solieri, Paolo Giudici, Luciana Vero, Francesca Comitini, Lucia Oro, Maurizio CianiAbstract:Over the last few decades, there has been a progressive increase in the ethanol content in wines due to global climate change and to the new wine styles that are associated with increased grape maturity. This increased ethanol content can have negative consequences on the sensory properties of the wines, human health, and economic aspects. Several microbiological approaches for decreasing the ethanol content have been suggested, such as strategies based on genetically modified yeasts, the adaptive evolution of yeasts, and the use of non- Saccharomyces yeast. In the present study, we investigated the interspecies and intraspecies variability of some non- Saccharomyces wine yeast species under anaerobic fermentation conditions. Across different grape juices and fermentation trials, Hanseniaspora uvarum , Zygosaccharomyces sapae , Zygosaccharomyces bailii, and Zygosaccharomyces bisporus promoted significant reductions in ethanol yield and fermentation efficiency in comparison with Saccharomyces cerevisiae . The diversion of alcoholic fermentation and the abundant formation of secondary compounds might explain the marked reduction in ethanol yield, as determined through the segregation of the majority of the strains according to their species attributes observed using principal component analysis. These data suggest that careful evaluation of interspecies and intraspecies biodiversity can be carried out to select yeast that produces low-ethanol yields.
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Unravelling genomic diversity of Zygosaccharomyces rouxii complex with a link to its life cycle
FEMS yeast research, 2013Co-Authors: Lisa Solieri, Tikam Chand Dakal, Maria Antonietta Croce, Paolo GiudiciAbstract:Zygosaccharomyces rouxii and the related species Zygosaccharomyces sapae (hereafter referred to as Z. rouxii complex) are protoploid hemiascomycete yeasts relevant in the elaboration and spoilage of foodstuff. Divergence of Z. rouxii complex before whole genome duplication, leading to the genus Saccharomyces, makes these yeasts very attractive for genome evolution study. Relatively little is known, however, about the diversity in this branch at the genetic and physiological levels. In this work, we investigated Z. rouxii complex, encompassing strains that in other works have been studied separately and comparing them in a comprehensive way. We showed that the majority of strains are unusually heterogeneous in their ribosomal DNA, a signal of relaxation of concerted evolution. Further analysis showed that they have hypervariable karyotypes, different levels of ploidy, and that housekeeping markers vary both in copy number and sequence. Overall, the results provide compelling evidence that the strains considered in this study are a complex of haploid, aneuploid and diploid mosaic lineages. The reproductive mode and life cycle of Zygosaccharomyces could lead to this unsuspected diversity.
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Zygosaccharomyces sapae sp. nov., isolated from Italian traditional balsamic vinegar.
International Journal of Systematic and Evolutionary Microbiology, 2012Co-Authors: Lisa Solieri, Tikam Chand Dakal, Paolo GiudiciAbstract:Fourteen yeast isolates were recovered from two traditional balsamic vinegar (TBV) samples collected in the provinces of Modena and Reggio Emilia, Italy. Microsatellite-primed-PCR (MSP-PCR) was used to de-replicate the isolate collection into two representative strains, ABT301T and ABT601. Phylogenetic analysis based on the D1/D2 domains of the 26S rRNA gene indicated that these strains represented a distinct species of the genus Zygosaccharomyces, closely related to Zygosaccharomyces rouxii and Zygosaccharomyces mellis. Physiological and morphological tests supported the recognition of a novel taxon of halotolerant, osmotolerant, non-psychrotolerant and maltose-fermentation-negative yeasts showing a chain or star-shaped pattern of budding cells, which remained attached to each other. Morphological observations offered evidence of ascospore formation. A novel species, Zygosaccharomyces sapae sp. nov., is proposed to accommodate these strains, with strain ABT301T ( = CBS 12607T = MUCL 54092T) as the type strain. Based on D1/D2 domain phylogenetic analysis, the novel strains shared the highest sequence similarity (100 %) with Zygosaccharomyces sp. strain NCYC 3042, previously isolated from sugar [James, S. A., Bond, C. J., Stratford, M. & Roberts, I. N. (2005). FEMS Yeast Res 5, 747–755]. However, based on phylogenetic (internal transcribed spacers, ITS), PCR fingerprinting and physiological analyses, marked differences were observed between the novel species and strain NCYC 3042, and these results are discussed in more detail.
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Yeasts associated to Traditional Balsamic Vinegar: Ecological and technological features
International journal of food microbiology, 2007Co-Authors: Lisa Solieri, Paolo GiudiciAbstract:Traditional Balsamic Vinegar (TBV) is an Italian homemade vinegar made with cooked grape must through a three-step process: conversion of sugars to ethanol by naturally occurring yeasts; oxidation of ethanol to acetic acid by acetic acid bacteria (AAB); and, finally, at least 12-years ageing. The cooked must is a selective and stressful medium for yeasts growth, due to its high sugar content and low pH values. Recent studies have shown that a large number of yeast species are involved in the fermentation, among them there are Zygosaccharomyces bailii, Zygosaccharomyces rouxii, Zygosaccharomyces pseudorouxii, Zygosaccharomyces mellis, Zygosaccharomyces bisporus, Zygosaccharomyces lentus, Hanseniaspora valbyensis, Hanseniaspora osmophila, Candida lactis-condensi, Candida stellata, Saccharomycodes ludwigii and Saccharomyces cerevisiae. Nevertheless, the TBV-associated yeast population could be even more complex and many other slow-growing or poorly cultivable species might contribute to cooked must fermentation. In this review the main TBV yeast species are described, pointing out their role in TBV production and their influence on final product quality. Finally, both future developments in TBV yeast community studies (culture-independent and metagenomic techniques) and technological advances in TBV making (use of starter culture) are discussed.
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A new putative Zygosaccharomyces yeast species isolated from traditional balsamic vinegar
Yeast (Chichester England), 2007Co-Authors: Lisa Solieri, Stefano Cassanelli, Paolo GiudiciAbstract:The taxonomic status and species number of the genus Zygosaccharomyces have rapidly changed in the last years. In this study, two new osmotolerant Zygosaccharomyces strains isolated from traditional balsamic vinegar, viz. ABT301 and ABT601, were investigated to elucidate their taxonomic relationships with Zygosaccharomyces rouxii species. A multi-gene sequence approach was employed, including regions of the rDNA repeat [5.8S, two internal transcribed spacers (ITS) and the 26S D1/D2 domain], COX2 mitochondrial gene and two nuclear genes (SOD2 and HIS3). Cloning and sequence analysis of 5.8S-ITS rDNA revealed that these strains bear an unusual polymorphism for this region. Three highly divergent 5.8S-ITS sequences were detected, one identical to Z. rouxii, the other two showing some relatedness to Z. mellis. Sequence and gene number polymorphism was also observed for the protein-encoding nuclear genes SOD2 and HIS3, as two copies for each gene different from those found in Z. rouxii were detected. Analysis of the D1/D2 26S domain showed that ABT301 and ABT601 have only one type of D1/D2 sequence statistically different from that of Z. rouxii. The findings obtained in this work suggest that the genomic background of strains ABT301 and ABT601 is different from the other Zygosaccharomyces species. We speculated that they could belong to a new putative species related to Z. rouxii.
Stephen A. James - One of the best experts on this subject based on the ideXlab platform.
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Zygosaccharomyces Barker (1901)
The Yeasts, 2011Co-Authors: Stephen A. James, Malcolm StratfordAbstract:Publisher Summary This chapter studies the genus Zygosaccharomyces. In the determination of the asexual reproduction it is seen that cell division is by multilateral budding on a narrow base. Cells are spherical, ovoid, or elongate. Pseudohyphae, if formed, are generally not well differentiated, and true hyphae are not produced. In sexual reproduction it is found that the asci are persistent and are generally formed by conjugation, either between a cell and its bud or, more frequently, between independent cells, often with both cells producing ascospores, thus giving rise to a dumbbell-shaped ascus. Ascospores are smooth and globose to ellipsoidal, and there are one to four per ascus. The chapter also discusses physiology/biochemistry and phylogenetic placement of the genus in which glucose is fermented, but not galactose. Nitrate is not assimilated and pellicles are not formed on liquid medium. Coenzyme Q-6 is produced and diazonium blue B reaction is negative. The type species taken is Zygosaccharomyces rouxii. The taxonomic re-evaluation followed extensive work by Winge and Lindegren and their collaborators, who reported that no clear distinction could be made between the Saccharomyces, Torulaspora, or Zygosaccharomyces. The genus currently comprises just six species, but this number is likely to increase in the future as the accuracy of yeast identification continues to improve through the use of DNA-based methods such as ribosomal RNA gene sequencing. With regard to Zygosaccharomyces, rRNA gene sequencing has already proved invaluable, both for differentiating between physiologically similar species and for identifying new species and Z. lentus.
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Molecular evidence for the existence of natural hybrids in the genus Zygosaccharomyces.
FEMS yeast research, 2005Co-Authors: Stephen A. James, Malcolm Stratford, C J Bond, Ian N. RobertsAbstract:26S rDNA D1/D2 sequencing was used to characterise a number of food-associated Zygosaccharomyces rouxii strains held at the National Collection of Yeast Cultures. In the course of this study, four strains (NCYC 1682, NCYC 3042, NCYC 3060 and NCYC 3061) were identified which appeared, based on their D1/D2 sequences, to belong to a novel Zygosaccharomyces species. However, subsequent sequence analysis showed that NCYC 1682, NCYC 3060 and NCYC 3061 possess two highly divergent copies of the nuclear-encoded ADE2, HIS3 and SOD2 genes, indicating these three strains are in fact hybrids. NCYC 3042, however, does appear to represent a novel species which may be hypothesized to have crossed with Z. rouxii and given rise to hybrid strains. Additional approaches to define precise taxonomic status and mechanisms of hybrid genome formation amongst yeast species are discussed.
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Sorbic acid resistance: the inoculum effect.
Yeast, 2000Co-Authors: Hazel Steels, Stephen A. James, Ian N. Roberts, Malcolm StratfordAbstract:Zygosaccharomyces is a genus associated with the more extreme spoilage yeasts. Zygosaccharomyces spoilage yeasts are osmotolerant, fructophiles (preferring fructose), highly-fermentative and extremely preservative-resistant. Zygosaccharomyces bailii can grow in the presence of commonly-used food preservatives, benzoic, acetic or sorbic acids, at concentrations far higher than are legally permitted or organolepically acceptable in foods. An inoculum effect has been described for many micro-organisms and antimicrobial agents. The minimum inhibitory concentration (MIC) increases with the size of the inoculum; large inocula at high cell density therefore require considerably higher concentrations of inhibitors to prevent growth than do dilute cell suspensions. A substantial inoculum effect was found using sorbic acid against the spoilage yeast Zygosaccharomyces bailii NCYC 1766. The inoculum effect was not caused by yeasts metabolizing or adsorbing sorbic acid, thereby lowering the effective concentration; was not due to absence of cell–cell signals in dilute cell suspensions; and was not an artefact, generated by insufficient time for small inocula to grow. The inoculum effect appeared to be caused by diversity in the populations of yeast cells, with higher probability of sorbic acid-resistant cells being present in large inocula. It was found that individual cells of Zygosaccharomyces bailii populations, grown as single cells in microtitre plate wells, were very diverse, varying enormously in resistance to sorbic acid. 26S ribosomal DNA sequencing did not detect differences between the small fraction of resistant ‘super cells’ and the average population. Re-inoculation of the ‘super cells’ after overnight growth on YEPD showed a normal distribution of resistance to sorbic acid, similar to that of the original population. The resistance phenotype was therefore not heritable and not caused by a genetically distinct subpopulation. It was concluded that resistance of the spoilage yeast Zygosaccharomyces bailii to sorbic acid was due to the presence of small numbers of phenotypically resistant cells in the population. Copyright © 2000 John Wiley & Sons, Ltd.
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Zygosaccharomyces lentus: a significant new osmophilic, preservative‐resistant spoilage yeast, capable of growth at low temperature
Journal of applied microbiology, 1999Co-Authors: Hazel Steels, Stephen A. James, Ian N. Roberts, Malcolm StratfordAbstract:Zygosaccharomyces lentus is a yeast species recently identified from its physiology and 18S ribosomal sequencing ( Steels et al. 1999 ).The physiological characteristics of five strains of this new yeast so far isolated were investigated, particularly those of technical significance for a spoilage yeast, namely temperature range, pH range, osmotolerance, sugar fermentation, resistance to food preservatives such as sorbic acid, benzoic acid and dimethyldicarbonate (DMDC; VelcorinTM). Adaptation to benzoic acid, and growth in shaking and static culture were also investigated. Zygosaccharomyces lentus strains grew over a wide range of temperature (4–25 °C) and pH 2·2–7·0. Growth at 4 °C was significant. Zygosaccharomyces lentus strains grew at 25–26 °C in static culture but were unable to grow in aerobic culture close to their temperature maximum. All Z. lentus strains grew in 60% w/v sugar and consequently, are osmotolerant. Zygosaccharomyces lentus strains could utilize sucrose, glucose or fructose as a source of fermentable sugar, but not galactose. Zygosaccharomyces lentus strains were resistant to food preservatives, growing in sorbic acid up to 400 mg l−1 and benzoic acid to 900 mg l−1 at pH 4·0. Adaptation to higher preservative concentrations was demonstrated with benzoic acid. Resistance to DMDC was shown to be greater than that of Z. bailii and Saccharomyces cerevisiae. This study confirms that Z. lentus is an important food spoilage organism potentially capable of growth in a wide range of food products, particularly low pH, high sugar foods and drinks. It is likely to be more significant than Z. bailii in the spoilage of chilled products.
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Zygosaccharomyces lentus sp. nov., a new member of the yeast genus Zygosaccharomyces Barker.
International Journal of Systematic and Evolutionary Microbiology, 1999Co-Authors: Hazel Steels, Ian N. Roberts, Malcolm Stratford, Matthew D Collins, C J Bond, Stephen A. JamesAbstract:Unusual growth characteristics of a spoilage yeast, originally isolated from spoiled whole-orange drink and previously identified as Zygosaccharomyces bailii, prompted careful re-examination of its taxonomic position. Smallsubunit rRNA gene sequences were determined for this strain and for four other strains also originally described as Z. bailii but which, in contrast to other strains of this species, grew poorly or not at all under aerobic conditior with agitation, failed to grew in the presence of 1% acetic acid and failed to grow at 30 °C. Comparative sequence analysis revealed that these strains represented a phylogenetically distinct taxon closely related to, but distinc from, Z. bailii and Zygosaccharomyces bisporus. Furthermore, sequence analysis of the internal transcribed spacer (ITS) region showed that, while all five strains had identical ITS2 sequences, they could be subdivided into two groups based on ITS1 sequences. Despite such minor inter-strain sequence variation, these yeasts could readily be distinguished from all other currently described Zygosaccharomyces species by using ITS sequences. On the basis of the phylogenetic results presented, a new species comprising the five strains Zygosaccharomyces lentus sp. nov., is described and supporting physiological data are discussed, including a demonstration that growth of this species is particularly sensitive to the presence of oxygen. The type strain of Z. lentus is NCYC D2627T.
Hazel Steels - One of the best experts on this subject based on the ideXlab platform.
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physiological characterization of spoilage strains of Zygosaccharomyces bailii and Zygosaccharomyces rouxii isolated from high sugar environments
International Journal of Food Microbiology, 2007Co-Authors: Patricia Martorell, Hazel Steels, Malcolm Stratford, Ma Teresa Fernandezespinar, Amparo QuerolAbstract:Two isolates of spoilage yeasts Zygosaccharomyces bailii and Zygosaccharomyces rouxii were obtained from a high sugar environment, in a factory producing candied fruit and nougat. Other strains, Z. bailii from other environments and other isolates from high sugar/salt environments were obtained for comparison (Zygosaccharomyces lentus, Candida magnoliae, Candida halophila and Pichia guilliermondii). A full physiological assessment of these isolates was carried out, of preservative and biocide resistance, osmotolerance, ethanol-tolerance, low pH resistance, degree of fermentation, and growth temperature and survival to pasteurisation. Results showed that the strains isolated from high sugar environments did not show extreme physiology. These were robust strains but within the normal parameters expected for the species. One exception to this was that the Z. bailii strains were abnormally able to grow at 37 degrees C. In all strains other than C. magnolia and C. halophila, cells were able to adapt to high levels of sugar. Cultures grown in high glucose concentrations were subsequently able to tolerate higher concentrations of glucose than previously. Similarly, high sugar was found to confer a degree of protection against pasteurisation, enabling survival in what would have otherwise been a lethal treatment. Isolates of Z. bailii showed a high level of resistance to preservatives such as sorbic acid, benzoic acid, acetic acid, cinnamic acid, and ethanol, and also to heat. Unexpectedly Z. bailii isolates were not exceptionally resistant to biocides such as peracetic acid, or hypochlorite. These results indicate that spoilage by yeasts such as Z. bailii may be better prevented by use of biocidal cleaning agents in the factory, rather than treating the food with preservatives.
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Physiological characterization of spoilage strains of Zygosaccharomyces bailii and Zygosaccharomyces rouxii isolated from high sugar environments.
International Journal of Food Microbiology, 2007Co-Authors: Patricia Martorell, Hazel Steels, Malcolm Stratford, Ma Teresa Fernández-espinar, Amparo QuerolAbstract:Abstract Two isolates of spoilage yeasts Zygosaccharomyces bailii and Zygosaccharomyces rouxii were obtained from a high sugar environment, in a factory producing candied fruit and nougat. Other strains, Z. bailii from other environments and other isolates from high sugar/salt environments were obtained for comparison (Zygosaccharomyces lentus, Candida magnoliae, Candida halophila and Pichia guilliermondii). A full physiological assessment of these isolates was carried out, of preservative and biocide resistance, osmotolerance, ethanol-tolerance, low pH resistance, degree of fermentation, and growth temperature and survival to pasteurisation. Results showed that the strains isolated from high sugar environments did not show extreme physiology. These were robust strains but within the normal parameters expected for the species. One exception to this was that the Z. bailii strains were abnormally able to grow at 37 °C. In all strains other than C. magnolia and C. halophila, cells were able to adapt to high levels of sugar. Cultures grown in high glucose concentrations were subsequently able to tolerate higher concentrations of glucose than previously. Similarly, high sugar was found to confer a degree of protection against pasteurisation, enabling survival in what would have otherwise been a lethal treatment. Isolates of Z. bailii showed a high level of resistance to preservatives such as sorbic acid, benzoic acid, acetic acid, cinnamic acid, and ethanol, and also to heat. Unexpectedly Z. bailii isolates were not exceptionally resistant to biocides such as peracetic acid, or hypochlorite. These results indicate that spoilage by yeasts such as Z. bailii may be better prevented by use of biocidal cleaning agents in the factory, rather than treating the food with preservatives.
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Zygosaccharomyces kombuchaensis the physiology of a new species related to the spoilage yeasts Zygosaccharomyces lentus and Zygosaccharomyces bailii
Fems Yeast Research, 2002Co-Authors: Hazel Steels, Ian N. Roberts, C J Bond, Steve James, Malcolm StratfordAbstract:Zygosaccharomyces kombuchaensis was recently discovered in the ‘tea fungus’ used to make fermented tea. Z. kombuchaensis was shown by ribosomal DNA sequencing to be a novel species, and a close relative of Zygosaccharomyces lentus, from which it could not be distinguished by conventional physiological tests. Z. lentus was originally established as a new taxon by growth at 4°C, sensitivity for heat and oxidative stress, and lack of growth in aerobic shaken culture at temperatures above 25°C. Subsequent analysis of Z. kombuchaensis reveals that this species shares these unusual characteristics, confirming its close genealogical relationship to Z. lentus. Detailed physiological data from a number of Z. kombuchaensis and Z. lentus strains clearly demonstrate that these two species can in fact be distinguished from one another based on their differing resistance/sensitivity to the food preservatives benzoic acid and sorbic acid. The spoilage yeasts Zygosaccharomyces bailii and Z. lentus are resistant to both acetic acid and sorbic acid, whereas Z. kombuchaensis is resistant to acetic acid but sensitive to sorbic acid. This would indicate that Z. kombuchaensis strains lack the mechanism for resistance to sorbic acid, but possess the means of resistance to acetic acid. This observation would therefore suggest that these two resistance mechanisms are different, and that in all probability acetic and sorbic acids inhibit yeast growth by different modes of action. Z. kombuchaensis strains were also sensitive to benzoic acid, again suggesting inhibition dissimilar from that to acetic acid.
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Sorbic acid resistance: the inoculum effect.
Yeast, 2000Co-Authors: Hazel Steels, Stephen A. James, Ian N. Roberts, Malcolm StratfordAbstract:Zygosaccharomyces is a genus associated with the more extreme spoilage yeasts. Zygosaccharomyces spoilage yeasts are osmotolerant, fructophiles (preferring fructose), highly-fermentative and extremely preservative-resistant. Zygosaccharomyces bailii can grow in the presence of commonly-used food preservatives, benzoic, acetic or sorbic acids, at concentrations far higher than are legally permitted or organolepically acceptable in foods. An inoculum effect has been described for many micro-organisms and antimicrobial agents. The minimum inhibitory concentration (MIC) increases with the size of the inoculum; large inocula at high cell density therefore require considerably higher concentrations of inhibitors to prevent growth than do dilute cell suspensions. A substantial inoculum effect was found using sorbic acid against the spoilage yeast Zygosaccharomyces bailii NCYC 1766. The inoculum effect was not caused by yeasts metabolizing or adsorbing sorbic acid, thereby lowering the effective concentration; was not due to absence of cell–cell signals in dilute cell suspensions; and was not an artefact, generated by insufficient time for small inocula to grow. The inoculum effect appeared to be caused by diversity in the populations of yeast cells, with higher probability of sorbic acid-resistant cells being present in large inocula. It was found that individual cells of Zygosaccharomyces bailii populations, grown as single cells in microtitre plate wells, were very diverse, varying enormously in resistance to sorbic acid. 26S ribosomal DNA sequencing did not detect differences between the small fraction of resistant ‘super cells’ and the average population. Re-inoculation of the ‘super cells’ after overnight growth on YEPD showed a normal distribution of resistance to sorbic acid, similar to that of the original population. The resistance phenotype was therefore not heritable and not caused by a genetically distinct subpopulation. It was concluded that resistance of the spoilage yeast Zygosaccharomyces bailii to sorbic acid was due to the presence of small numbers of phenotypically resistant cells in the population. Copyright © 2000 John Wiley & Sons, Ltd.
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Zygosaccharomyces lentus: a significant new osmophilic, preservative‐resistant spoilage yeast, capable of growth at low temperature
Journal of applied microbiology, 1999Co-Authors: Hazel Steels, Stephen A. James, Ian N. Roberts, Malcolm StratfordAbstract:Zygosaccharomyces lentus is a yeast species recently identified from its physiology and 18S ribosomal sequencing ( Steels et al. 1999 ).The physiological characteristics of five strains of this new yeast so far isolated were investigated, particularly those of technical significance for a spoilage yeast, namely temperature range, pH range, osmotolerance, sugar fermentation, resistance to food preservatives such as sorbic acid, benzoic acid and dimethyldicarbonate (DMDC; VelcorinTM). Adaptation to benzoic acid, and growth in shaking and static culture were also investigated. Zygosaccharomyces lentus strains grew over a wide range of temperature (4–25 °C) and pH 2·2–7·0. Growth at 4 °C was significant. Zygosaccharomyces lentus strains grew at 25–26 °C in static culture but were unable to grow in aerobic culture close to their temperature maximum. All Z. lentus strains grew in 60% w/v sugar and consequently, are osmotolerant. Zygosaccharomyces lentus strains could utilize sucrose, glucose or fructose as a source of fermentable sugar, but not galactose. Zygosaccharomyces lentus strains were resistant to food preservatives, growing in sorbic acid up to 400 mg l−1 and benzoic acid to 900 mg l−1 at pH 4·0. Adaptation to higher preservative concentrations was demonstrated with benzoic acid. Resistance to DMDC was shown to be greater than that of Z. bailii and Saccharomyces cerevisiae. This study confirms that Z. lentus is an important food spoilage organism potentially capable of growth in a wide range of food products, particularly low pH, high sugar foods and drinks. It is likely to be more significant than Z. bailii in the spoilage of chilled products.