FEMS yeast research最新文献

Fission yeast is the ideal model organism for studying telomere maintenance in higher eukaryotes. Telomere length has been directly correlated with life expectancy and the onset of aging-related diseases in mammals. In this study, we developed a novel simple, and reproducible method to measure the telomere length, by investigating the effect of caffeine and cisplatin on the telomere length in fission yeast. Hydroxyurea-synchronized fission yeast cells were exposed to 62 µM cisplatin and 8.67 mM caffeine treatments for 2 h, then their telomere lengths were evaluated with two different methods. First, the quantitative polymerase chain reaction (qPCR) assay was used as a confirmative method, where telomere length was determined relative to a single-copy gene in the genome. Second, the newly developed method standard polymerase chain reaction (PCR)/ImageJ assay assessed the telomere length based on the amplified PCR band intensity using a set of telomere primers, reflecting telomeric sequence availability in the genome. Both methods show a significant decrease and a notable telomere lengthening in response to cisplatin and caffeine treatments, respectively. The finding supports the accuracy and productivity of the standard PCR/ImageJ assay as it can serve as a quick screening tool to study the effect of suspected chemotherapeutic and antiaging drugs on telomere length in fission yeast.

The genus Hanseniaspora includes apiculate yeasts commonly found in fruit- and fermentation-associated environments. Their genetic diversity and evolutionary adaptations remain largely unexplored despite their ecological and oenological significance. This study investigated the phylogenetic relationships, genome structure, selection patterns, and phenotypic diversity of Hanseniaspora species isolated primarily from Australian wine environments, focusing on Hanseniaspora uvarum, the most abundant non-Saccharomyces yeast in wine fermentation. A total of 151 isolates were sequenced, including long-read genomes for representatives of the main phylogenetic clades. Comparative genomics revealed ancestral chromosomal rearrangements between the slow-evolving lineage (SEL) and fast-evolving lineage (FEL) that could have contributed to their evolutionary split, as well as significant loss of genes associated with mRNA splicing, chromatid segregation and signal recognition particle protein targeting in the FEL. Pangenome analysis within H. uvarum identified extensive copy number variation, particularly in genes related to xenobiotic tolerance and nutrient transport. Investigation into the selective landscape following the FEL/SEL divergence identified diversifying selection in 229 genes in the FEL, with significant enrichment in genes within the lysine biosynthetic pathway. Furthermore, phenotypic screening of 116 isolates revealed substantial intraspecific diversity, with specific species exhibiting enhanced ethanol, osmotic, copper, SO₂, and cold tolerance.

The Wickerhamiella/Starmerella (W/S) yeast clade has recently gained attention as a "treasure trove" of metabolic diversity, characterized by unusual pathways shaped through complex evolutionary events. One of their most distinctive traits is their specialized sugar metabolism, which allows them to thrive in sugar-rich environments. While their role in sugar utilization is well established, emerging evidence suggests that some W/S species can also metabolize hydrophobic compounds, indicating a broader capacity for lipid-related processes. For instance, several W/S species produce sophorolipids (SLs)-a class of glycolipids with commercial applications as sustainable biosurfactants. This ability has sparked growing interest in their potential to synthesize a diverse range of lipids, including glycolipids and dicarboxylic acids. This mini-review explores the evolution and distinctive metabolic features of the W/S clade, focusing not only on its well-characterized sugar metabolism but also on its lesser-known lipid metabolism. Particular attention is given to SL production and the expansion and diversity of cytochrome P450 family 52 enzymes within this underexplored group, emphasizing their biotechnological potential in lipid biosynthesis and their promising applications in sustainable bioprocesses.

A vast literature explores a model system that consists of a prey crustacean, the water flea Daphnia spp., and an obligately pathogenic yeast that has been referred to as Metschnikowia bicuspidata and thought to represent the material used by Metschnikoff in his study of innate immunity. Typification of species bearing that name and indeed the whole genus has been problematic as regards yeasts that only grow or form aciculate ascospores in hospite. The neotype of M. bicuspidata, unlike the Daphnia parasite, is easily cultured on a variety of laboratory media, although it too can cause serious infections in a variety of mostly aquatic animals. It has become evident that the Daphnia parasite studied by Metschnikoff or current workers is not closely related to M. bicuspidata as currently understood. Analysis of whole genome DNA extracted from the yeast repeatedly found in infected Daphnia specimens shows that it belongs to the recently circumscribed genus Australozyma. The yeast is described here as Australozyma monospora sp. nov. The species, although haplontic and heterothallic, forms single-spored asci without mating. It also appears that all species in the genus are restricted to asexual reproduction, which may explain their rare status. The holotype is MICH 346683. The name is registered in Mycobank under the number MB 859667.

The growing challenges posed by global warming and the demand for sustainable food and feed resources underscore the need for robust microbial platforms in bioprocessing. Thermotolerant yeasts have emerged as promising candidates due to their ability to thrive at elevated temperatures and other industrially relevant stresses. This review examines the industrial potential of thermotolerant yeasts in the context of climate change, emphasizing how their resilience can lead to more energy-efficient and cost-effective bioprocesses. Particular attention is paid to the thermodynamic implications of yeast metabolism under heat stress, especially in bioethanol production and methanol metabolism in methylotrophic yeasts, where metabolic heat generation plays a critical role. The cellular and molecular mechanisms underlying thermotolerance are also reviewed, including heat shock sensing mechanisms, the protection of biomolecules, and membrane and cell wall integrity. Advances in genetic and metabolic engineering aimed at enhancing these traits are also highlighted. By integrating current insights into the molecular and cellular mechanisms of thermotolerance, along with recent technological advancements, this review outlines the advantages of high-temperature operations and positions thermotolerant yeasts as vital components of future sustainable bioproduction systems.

Saccharomyces cerevisiae is a promising microbial cell factory. However, the overflow metabolism, known as the Crabtree effect, directs the majority of the carbon source toward ethanol production, in many cases, resulting in low yields of other target chemicals and byproducts accumulation. To construct Crabtree-negative S. cerevisiae, the deletion of pyruvate decarboxylases and/or ethanol dehydrogenases is required. However, these modifications compromises the growth of the strains on glucose. This review discusses the metabolic engineering approaches used to eliminate ethanol production, the efforts to alleviate growth defect of Crabtree-negative strains, and the underlying mechanisms of the growth rescue. In addition, it summarizes the applications of Crabtree-negative S. cerevisiae in the synthesis of various chemicals such as lactic acid, 2,3-butanediol, malic acid, succinic acid, isobutanol, and others.

The yeast Saccharomyces cerevisiae converts amino acids into volatile compounds with fruity and floral aromas during fermentation. These amino acid-derived aroma compounds play a critical role in defining the taste and flavor of alcoholic beverages such as sake, beer, and wine. The productivity of amino acid-derived aroma compounds depends on the intracellular availability of their precursor amino acids. Therefore, breeding yeast strains that accumulate amino acids provides a practical approach to developing alcoholic beverages with more unique and attractive sensory characteristics. In this minireview, we describe the isolation of yeast strains that overproduce branched-chain amino acids and phenylalanine, obtained through conventional mutagenesis of industrial brewing yeasts. We also discuss the mechanisms responsible for the increased production of these amino acids in the mutant strains, including altered feedback regulation and transcriptional control of key enzymes involved in their biosynthesis. In addition, we briefly introduce a plasmid-free genome editing system that enables precise modification of metabolic pathways without the integration of foreign DNA, allowing the construction of strains that are not classified as genetically modified organisms. This method represents a promising tool that allows flexible and fine-tuned engineering of yeast metabolic pathways, including the development of strains with tailored aroma profiles.

Flocculation in Saccharomyces cerevisiae is a critical phenotype with ecological and industrial significance. This study aimed to functionally dissect the contributions of individual FLO genes (FLO1, FLO5, FLO9, FLO10, FLO11) to flocculation by employing an optogenetic circuit (OptoQ-AMP5) for precise, light-inducible control of gene expression. A FLO-null platform yeast strain was engineered allowing the expression of individual FLO genes without native background interference. Each FLO gene was reintroduced into the FLO-null background under the control of OptoQ-AMP5. Upon light induction, strains expressing FLO1, FLO5, or FLO10 demonstrated strong flocculation, with FLO1 and FLO5 forming large and structurally distinct aggregates. FLO9 induced a weaker phenotype. Sugar inhibition assays revealed distinct sensitivities among flocculins, notably FLO9's novel sensitivity to fructose and maltotriose. Additionally, FLO-induced changes in cell surface hydrophobicity were quantified, revealing that FLO10 and FLO1 conferred the greatest hydrophobicity, correlating with their aggregation strength. This work establishes a robust platform for investigating flocculation mechanisms in yeast with temporal precision. It highlights the phenotypic diversity encoded within the FLO gene family and their differential responses to environmental cues. The optogenetic system provides a valuable tool for both fundamental studies and the rational engineering of yeast strains for industrial fermentation processes requiring controlled flocculation.

Microbial fermentation can provide a sustainable and cost-effective alternative to traditional plant extraction to produce natural food colours. Betalains are a class of yellow to red water-soluble pigments. Even though over 80 betalain variants are known, betanin is the only betalain available as a food colourant on the market. Many variants are acylated, which can enhance their stability and change the hue, but very few acyltransferases responsible for the acylation are known. Therefore, we mined the transcriptomes of Celosia argentea var. cristata and Hylocereus polyrhizus for BAHD acyltransferases, enzymes likely involved in betalain acylation. In vivo screening of the enzymes in betanin-producing Saccharomyces cerevisiae revealed that the acyltransferase HpBAHD3 from H. polyrhizus malonylates betanin, forming phyllocactin (6'-O-malonyl-betanin). This is the first identification of a BAHD acyltransferase involved in betalain biosynthesis. Expression of HpBAHD3 in a Yarrowia lipolytica strain engineered for high betanin production led to near-complete conversion of betanin to phyllocactin. In fed-batch fermentation, the strain produced 1.95 ± 0.024 g/l phyllocactin in 60 h. This study expands the range of natural food colourants produced through microbial fermentation and contributes to elucidating the biosynthesis pathway of acylated betalains.

Lager beer is traditionally fermented using Saccharomyces pastorianus. However, the limited availability of lager yeast strains restricts the potential range of beer profiles. Recently, Saccharomyces eubayanus strains showed the potential to impart novel aromas to beer, with slower fermentation rates than commercial strains. Here, we applied experimental evolution to nine S. eubayanus strains using three different selective conditions to generate improved strains to fermentative environments. We observed environment-dependent fitness changes across strains, with ethanol-enriched media resulting in the greatest fitness improvement. We identified subtelomeric genomic changes in a deficient fermentative strain underlying the greatest fitness improvement. Gene expression analysis and genome sequencing identified genes associated with oxidative stress, amino acid metabolism, sterol biosynthesis, and vacuole morphology underlying differences between evolved and the ancestral strain, revealing the cellular processes underlying fermentation improvement. A hybridization strategy between two evolved strains allowed us to expand the phenotypic space of the F2 segregants, obtaining strains with a 13.7% greater fermentative capacity relative to the best evolved parental strains. Our study highlights the potential of integrating experimental evolution and hybridization to enhance the fermentation capacity of wild yeast strains, offering strengthened solutions for industrial applications and highlighting the potential of Patagonian S. eubayanus in brewing.