FEMS yeast research最新文献

Malassezia are the dominant commensal yeast species of the human skin microbiota and are associated with inflammatory skin diseases, such as atopic eczema (AE). The Mala s 1 allergen of Malassezia sympodialis is a β-propeller protein, inducing both IgE and T-cell reactivity in AE patients. We demonstrate by immuno-electron microscopy that Mala s 1 is mainly located in the M. sympodialis yeast cell wall. An anti-Mala s 1 antibody did not inhibit M. sympodialis growth suggesting Mala s 1 may not be an antifungal target. In silico analysis of the predicted Mala s 1 protein sequence identified a motif indicative of a KELCH protein, a subgroup of β-propeller proteins. To test the hypothesis that antibodies against Mala s 1 cross-react with human skin (KELCH) proteins we examined the binding of the anti-Mala s 1 antibody to human skin explants and visualized binding in the epidermal skin layer. Putative human targets recognized by the anti-Mala s 1 antibody were identified by immunoblotting and proteomics. We propose that Mala s 1 is a KELCH-like β-propeller protein with similarity to human skin proteins. Mala s 1 recognition may trigger cross-reactive responses that contribute to skin diseases associated with M. sympodialis.

The antiaging properties of metformin used for the treatment of type-2 diabetes mellitus have been studied extensively, but there is more to discover regarding underlying mechanisms. Here, we show that metformin significantly prolongs the chronological lifespan (CLS) of Schizosaccharomyces pombe through mechanisms similar to those observed in mammalian cells and other model organisms. While the presence of metformin in the medium caused an increase in carbohydrate consumption and ATP production, it reduced reactive oxygen species production and alleviate oxidative damage parameters such as lipid peroxidation and carbonylated proteins. We also tested whether the effect of metformin changed with the time it was added to the medium and observed that the lifespan-prolonging effect of metformin was related to the glucose concentration in the medium and did not prolong lifespan when added after glucose was completely depleted in the medium. On the other hand, cells inoculated in glucose-free medium containing metformin also showed extended lifespan suggesting that mechanisms other than that solely depend on glucose availability may be involved in extending the lifespan. These results suggest that metformin prolongs lifespan especially affecting energy metabolism and stress resistance capacity and that fission yeast can be effectively used when investigating the antiaging mechanisms of metformin.

Lytic enzymes secreted by Kluyveromyces marxianus can lyse Saccharomyces cerevisiae cells. Their ability to hydrolyze yeast cell walls can be used in biotechnological applications, such as the production of glucans and protoplasts, as well as a biological control agent against plant pathogenic fungi. Herein, 27 proteins secreted by K. marxianus were identified by mass spectrometry analyses. Importantly, 14 out of the 27 proteins were classified as hydrolases. Indeed, the enzyme extract secreted by K. marxianus caused damage to S. cerevisiae cells and reduced yeast cell viability. Moreover, K marxianus inhibited spore germination and mycelial growth of the phytopathogenic fungus Botrytis cinerea in simultaneous cocultivation assays. We suggest that this inhibition may be partially related to the yeast's ability to secrete lytic enzymes. Consistent with the in vitro antagonistic tests, K. marxianus was able to protect strawberry fruits inoculated with B. cinerea. Therefore, these findings suggest that K. marxianus possesses potential as a biocontrol agent against strawberry gray mold during the postharvest stage and may also have potential against other phytopathogenic fungi by means of its lytic enzymatic arsenal.

Sake yeasts have a range of brewing characteristics that are particularly beneficial for sake making including high ethanol fermentability, high proliferative capacity at low temperatures, lactic acid tolerance, and high ester productivity. On the other hand, sake yeasts also accumulate a diverse range of functional components. For example, significantly greater accumulation of S-adenosylmethionine (SAM), a compound that plays important regulatory roles in a range of biological processes as a major donor of methyl groups, occurs in sake yeasts compared to other microorganisms. Significantly greater accumulation of folate, a bioactive water-soluble vitamin (vitamin B9), also occurs in sake yeasts compared to laboratory yeasts, and the methyl group on SAM is supplied by folate. Accordingly, fully characterizing 'sake yeast identity' requires detailed understanding of the mechanisms underlying both the nutritional characteristics (functional components) and the brewing characteristics in sake yeasts. Therefore, this mini-review focuses on the accumulation of SAM and folate in sake yeast including descriptions of the genes known to contribute to SAM and folate accumulation and the underlying mechanisms.

Apiculate yeasts belonging to the genus Hanseniaspora are predominant on grapes and other fruits. While some species, such as Hanseniaspora uvarum, are well known for their abundant presence in fruits, they are generally characterized by their detrimental effect on fermentation quality because the excessive production of acetic acid. However, the species Hanseniaspora vineae is adapted to fermentation and currently is considered as an enhancer of positive flavour and sensory complexity in foods. Since 2002, we have been isolating strains from this species and conducting winemaking processes with them. In parallel, we also characterized this species from genes to metabolites. In 2013, we sequenced the genomes of two H. vineae strains, being these the first apiculate yeast genomes determined. In the last 10 years, it has become possible to understand its biology, discovering very peculiar features compared to the conventional Saccharomyces yeasts, such as a natural and unique G2 cell cycle arrest or the elucidation of the mandelate pathway for benzenoids synthesis. All these characteristics contribute to phenotypes with proved interest from the biotechnological point of view for winemaking and the production of other foods.

This study investigated the potential of wastepaper hydrolysate as a sustainable and low-cost carbon source for single-cell oil and protein production, attending to the growing need for alternative feedstocks and waste management strategies. Wastepaper, characterized by its high carbohydrate content, was subjected to enzymatic and chemo-enzymatic treatments for carbohydrate release. The chemo-enzymatic treatment performed better, yielding 65.3 g l-1 of fermentable sugars. A total of 62 yeast strains were screened for single-cell oil accumulation, identifying Rhodotorula mucilaginosa M1K4 as the most advantageous oleaginous yeast. M1K4 lipid production was optimized in liquid culture, and its fatty acid profile was analyzed, showing a high content of industrially valuable fatty acids, particularly palmitic (28%) and oleic (51%). Batch-culture of M1K4 in a 3-l reactor demonstrated the strain's ability to utilize wastepaper hydrolysate as a carbon source, with dry cell weight, total lipid and protein production of 17.7 g l-1, 4.5 g l-1, and 2.1 g l-1, respectively. Wastepaper as a substrate provides a sustainable solution for waste management and bioproduction. This research highlights the potential of R. mucilaginosa for lipid and protein production from wastepaper hydrolysate.

Budding yeast uses the TORC1-Sch9p and cAMP-PKA signalling pathways to regulate adaptations to changing nutrient environments. Dynamic and single-cell measurements of the activity of these cascades will improve our understanding of the cellular adaptation of yeast. Here, we employed the AKAR3-EV biosensor developed for mammalian cells to measure the cellular phosphorylation status determined by Sch9p and PKA activity in budding yeast. Using various mutant strains and inhibitors, we show that AKAR3-EV measures the Sch9p- and PKA-dependent phosphorylation status in intact yeast cells. At the single-cell level, we found that the phosphorylation responses are homogenous for glucose, sucrose, and fructose, but heterogeneous for mannose. Cells that start to grow after a transition to mannose correspond to higher normalized Förster resonance energy transfer (FRET) levels, in line with the involvement of Sch9p and PKA pathways to stimulate growth-related processes. The Sch9p and PKA pathways have a relatively high affinity for glucose (K0.5 of 0.24 mM) under glucose-derepressed conditions. Lastly, steady-state FRET levels of AKAR3-EV seem to be independent of growth rates, suggesting that Sch9p- and PKA-dependent phosphorylation activities are transient responses to nutrient transitions. We believe that the AKAR3-EV sensor is an excellent addition to the biosensor arsenal for illuminating cellular adaptation in single yeast cells.

Genome ploidy of Zygosaccharomyces rouxii is an intriguing topic in the field of industrial yeast research. However, the evolutionary relationship between the genome of Z. rouxii and other Zygosaccharomyces species is complex and not completely understood. In this study, we determined the genome sequences of Z. rouxii NCYC 3042, also referred to as 'Z. pseudorouxii,' and Z. mellis CBS 736T. We also conducted comparative analysis of the yeast genomes of a total of 21 strains, including 17 strains of nine Zygosaccharomyces species. This comparative genomics revealed that 17 Zygosaccharomyces strains are classified into four groups consisting of nine genome types: (i) Z. rouxii, Z. mellis, Z. sapae, Z. siamensis, and 'Candida versatilis' t-1 belong to the group Rouxii sharing four related genome types (Rouxii-1 to Rouxii-4), (ii) Z. bailii, Z. parabailii, and Z. pseudobailii belong to the group Bailii sharing three related genome types (Bailii-1 to Bailii-3), (iii and iv) Z. bisporus and Z. kombuchaensis belong to the groups Bisporus and Kombuchaensis, respectively, which each have haploid genomes. The Zygosaccharomyces genome seems to have acquired complexity and diversity through evolutionary events such as interspecies hybridization, reciprocal translocation, and diploidization of these nine genome types.

Rice contains numerous nutrients and biologically active compounds. The phytochemical composition of rice varies among cultivars, leading to diversities in biological activities. Fermentation is an efficient way of improving nutrient bioavailability and the functional properties of raw materials. It enhances and/or synthesizes the compounds with health-promoting or decreased antinutritive compounds during the fermentation process. Rice-based fermented products have been reported for enhancing various biological activities, including antioxidant, anti-cancer, anti-diabetes, anti-wrinkle and anti-melanogenesis activities. Melanogenesis, melanin biosynthesis, is the cause of human skin pigmentation; however, the accumulation of melanin leads to skin hyper-pigmentary disorders, such as freckles and melasma. In this review, the information on rice-based fermented products has been assembled to illustrate the fermented rice properties, especially melanogenesis inhibition activity, including functional roles of the microorganisms in the fermented rice products.