Transcriptomic-metabolomic analysis reveals the effect of copper toxicity on fermentation properties in Saccharomyces cerevisiae

Copper is one of the unavoidable heavy metals in wine production. In this study, the effects on fermentation performance and physiological metabolism of Saccharomyces cerevisiae under copper stress were investigated. EC1118 was the most copper-resistant among the six strains. The ethanol accumulation of EC1118 was 26.16-20 mg/L Cu2+, which was 1.90-3.15 times higher than that of other strains. The fermentation rate was significantly reduced by copper, and the inhibition was relieved after 4-10 days of adjustment. Metabolomic-transcriptomic analysis revealed that amino acid and nucleotide had the highest number of downregulated and upregulated differentially expressed metabolites, respectively. The metabolism of fructose and mannose was quickly affected, which then triggered the metabolism of galactose in copper stress. Pathways such as oxidative and organic acid metabolic processes were significantly affected in the early time, resulting in a significant decrease in the amount of carboxylic acids. The pathways related to protein synthesis and metabolism under copper stress, such as translation and peptide biosynthetic process, was also significantly affected. In conclusion, this study analyzed the metabolite-gene interaction network and molecular response during the alcohol fermentation of S. cerevisiae under copper stress, providing theoretical basis for addressing the influence of copper stress in wine production.

The distribution of beneficial mutational effects between two sister yeast species poorly explains natural outcomes of vineyard adaptation

Domesticated strains of Saccharomyces cerevisiae have adapted to resist copper and sulfite, two chemical stressors commonly used in winemaking. S. paradoxus, has not adapted to these chemicals despite being consistently present in sympatry with S. cerevisiae in vineyards. This contrast represents a case of apparent evolutionary constraints favoring greater adaptive capacity in S. cerevisiae. In this study, we used a comparative mutagenesis approach to test whether S. paradoxus is mutationally constrained with respect to acquiring greater copper and sulfite resistance. For both species, we assayed the rate, effect size, and pleiotropic costs of resistance mutations and sequenced a subset of 150 mutants isolated from our screen. We found that the distributions of mutational effects displayed by the two species were very similar and poorly explained the natural pattern. We also found that chromosome VIII aneuploidy and loss of function mutations in PMA1 confer copper resistance in both species, whereas loss of function mutations in REG1 were only a viable route to copper resistance in S. cerevisiae. We also observed a single de novo duplication of the CUP1 gene in S. paradoxus but none in S. cerevisiae. For sulfite, loss of function mutations in RTS1 and KSP1 confer resistance in both species, but mutations in RTS1 have larger average effects in S. paradoxus. Our results show that even when the distributions of mutational effects are largely similar, species can differ in the adaptive paths available to them. They also demonstrate that assays of the distribution of mutational effects may lack predictive insight concerning adaptive outcomes.

Once upon a Time, There Was a Piece of Wood: Present Knowledge and Future Perspectives in Fungal Deterioration of Wooden Cultural Heritage in Terrestrial Ecosystems and Diagnostic Tools

Wooden Cultural Heritage (WCH) represents a significant portion of the world's historical and artistic heritage, consisting of immovable and movable artefacts. Despite the expertise developed since ancient times to enhance its durability, wooden artefacts are inevitably prone to degradation. Fungi play a pivotal role in the deterioration of WCH in terrestrial ecosystems, accelerating its decay and leading to alterations in color and strength. Reviewing the literature of the last 25 years, we aimed to provide a comprehensive overview of fungal diversity affecting WCH, the biochemical processes involved in wood decay, and the diagnostic tools available for fungal identification and damage evaluation. Climatic conditions influence the occurrence of fungal species in threatened WCH, characterized by a prevalence of wood-rot fungi (e.g., Serpula lacrymans, Coniophora puteana) in architectural heritage in temperate and continental climates and Ascomycota in indoor and harsh environments. More efforts are needed to address the knowledge fragmentation concerning biodiversity, the biology of the fungi involved, and succession in the degradative process, which is frequently centered solely on the main actors. Multidisciplinary collaboration among engineers, restorers, and life sciences scientists is vital for tackling the challenges posed by climate change with increased awareness. Traditional microbiology and culture collections are fundamental in laying solid foundations for a more comprehensive interpretation of big data.

Yeast communities of a North American hybrid wine grape differ between organic and conventional vineyards

AIMS

To compare the species diversity and composition of indigenous yeast communities of hybrid grapes from conventionally and organically cultivated vineyards of an emerging cool-climate wine producing region.

METHODS AND RESULTS

Illumina MiSeq sequences from L'Acadie blanc grape musts were processed and filtered to characterize indigenous yeast communities in organic and conventional vineyards of the Annapolis Valley wine region in Nova Scotia, Canada. While cultivation practice was not associated with yeast diversity or species richness, there was a strong effect on yeast community composition, with conventional vineyards characterized by higher proportions of Sporidiobolales and Filobasidium magnum, and organic vineyards supporting Filobasidium species other than F. magnum and higher proportions of Symmetrospora. There was also variation in yeast community composition among individual vineyards, and from year to year.

CONCLUSIONS

This is the first comprehensive assessment of yeasts associated with hybrid grapes grown using different cultivation practices in a North American cool climate wine region. Communities were dominated by basidiomycete yeasts and species composition of these yeasts differed significantly between vineyards employing organic and conventional cultivation practices. The role of basidiomycete yeasts in winemaking is not well understood, but some species may influence wine characteristics.

COS-OGA Applications in Organic Vineyard Manage Major Airborne Diseases and Maintain Postharvest Quality of Wine Grapes

In most wine-growing countries of the world the interest for organic viticulture and eco-friendly grape production processes increased significantly in the last decade. Organic viticulture is currently dependent on the availability of Cu and S compounds, but their massive use over time has led to negative effects on environment health. Consequently, the purpose of this study was to evaluate the effectiveness of alternative and sustainable treatments against powdery mildew, gray mold and sour rot under the field conditions on Nero d’Avola and Inzolia Sicilian cultivars. In detail, the efficacy of COS-OGA, composed by a complex of oligochitosans and oligopectates, and its effects in combination with arbuscular mycorrhizal fungi (AMF) were evaluated to reduce airborne disease infections of grape. COS-OGA combined with AMF induced a significant reduction in powdery mildew severity both on Nero d’Avola and Inzolia with a mean percentage decrease of about 15% and 33%, respectively. Moreover, COS-OGA alone and combined with AMF gave a good protection against gray mold and sour rot with results similar to the Cu–S complex (performance in disease reduction ranging from 65 to 100%) on tested cultivars. Similarly, the COS-OGA and AMF integration provided good performances in enhancing average yield and did not negatively impact quality and microbial communities of wine grape. Overall, COS-OGA alone and in combination could be proposed as a valid and safer option for the sustainable management of the main grapevine pathogens in organic agroecosystems.

Network Properties of Local Fungal Communities Reveal the Anthropogenic Disturbance Consequences of Farming Practices in Vineyard Soils

Agroecosystems are human-managed ecosystems subject to generalized ecological rules. Understanding the ecology behind the assembly and dynamics of soil fungal communities is a fruitful way to improve management practices and plant productivity. Thus, monitoring soil health would benefit from the use of metrics that arise from ecological explanations that can also be informative for agricultural management. Beyond traditional biodiversity descriptors, community-level properties have the potential of informing about particular ecological situations. Here we assess the impact of different farming practices in a survey of 350 vineyard soils from the United States and Spain by estimating network properties based on spatial associations. Our observations using traditional approaches show results concurring with previous literature: the influence of geographic and climatic factors on sample distributions, or different operational taxonomic unit (OTU) compositions depending on agricultural managements. Furthermore, using network properties, we observe that fungal communities ranged from dense arrangements of associations to a sparser structure of associations, indicating differential levels of niche specialization. We detect fungal arrangements capable of thriving in wider or smaller ranges of temperature, revealing that niche specialization may be a critical soil process impacting soil health. Low-intervention practices (organic and biodynamic managements) promoted densely clustered networks, describing an equilibrium state based on mixed collaborative communities. In contrast, conventionally managed vineyards had highly modular sparser communities, supported by a higher coexclusion proportion. Thus, we hypothesize that network properties at the community level may help to understand how the environment and land use can affect community structure and ecological processes in agroecosystems.

IMPORTANCE Soil fungal communities play a key role in agroecosystem sustainability. The complexity of fungal communities, at both taxonomic and functional levels, makes it difficult to find clear patterns connecting community composition with ecosystem function and to understand the impact of biotic (interspecies interactions) and abiotic (e.g., climate or anthropogenic disturbances) factors on it. Here we combine network analysis methods and properties, proposing a novel analytical approach: to infer ecological properties from local networks, which we apply to the study of fungal communities in vineyard soils. We conclude that different levels of farming intensification may lead to different ecological strategies in soil fungal communities settled by particular association arrangements.

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Features of basidiomycetous yeasts from grapes and apples associated with crop environment and fermenting juice

AIMS

The characterization of grape and apple yeasts was carried out to investigate the ecology of basidiomycetes associated with crop environment and fermenting juice.

METHODS AND RESULTS

A total of 15 basidiomycetous strains were analysed for plant-growth promoting properties, sensitivity to fungicides and features related to their survival in fermenting juice (low pH, SO₂ and ethanol sensitivity). Only one strain displayed 1-aminocyclopropane-1-carboxylate deaminase activity, whereas other strains were able to produce ammonia and indole-3-acetic acid, solubilize calcium phosphate, and display catalase activity and antagonism against Botrytis cinerea. Strains presented great variability in their sensitivity to fungicides. Rhodotorula mucilaginosa Yl26 and Sporobolomyces agrorum PYCC 8108^T displayed low sensitivity to all fungicides, with high tolerance to SO₂ and ethanol, and were able to survive in fermenting grape and apple juice.

CONCLUSIONS

This study revealed the diversity of basidiomycetous yeasts in the important physiological traits that affect their growth, either in the crop environment or in fermenting juice.

SIGNIFICANCE AND IMPACT OF THE STUDY

Identify the possibility of selective effects of fungicide treatments on basidiomycetous yeasts that could offer benefits for grapevines and apple trees, as well as the survival of strains that are better adapted to fermenting juice and that potentially have a role in the aroma of beverages.

Genomic Adaptation of Saccharomyces Species to Industrial Environments

The budding yeast has been extensively studied for its physiological performance in fermentative environments and, due to its remarkable plasticity, is used in numerous industrial applications like in brewing, baking and wine fermentations. Furthermore, thanks to its small and relatively simple eukaryotic genome, the molecular mechanisms behind its evolution and domestication are more easily explored. Considerable work has been directed into examining the industrial adaptation processes that shaped the genotypes of species and hybrids belonging to the Saccharomyces group, specifically in relation to beverage fermentation performances. A variety of genetic mechanisms are responsible for the yeast response to stress conditions, such as genome duplication, chromosomal re-arrangements, hybridization and horizontal gene transfer, and these genetic alterations are also contributing to the diversity in the Saccharomyces industrial strains. Here, we review the recent genetic and evolutionary studies exploring domestication and biodiversity of yeast strains.

Impact of Chemical and Alternative Fungicides Applied to Grapevine cv Nebbiolo on Microbial Ecology and Chemical-Physical Grape Characteristics at Harvest

Viticulture is a cropping system in which treatment against fungal diseases (in particular powdery and downy mildews) can be extremely frequent. Accordingly, a reduction in antimicrobial treatments and the application of environmentally-friendly compounds are becoming increasingly important for a more sustainable viticulture. In addition to their effect against pathogens, the impact of these products on the quality of the grapes is very important for the oenological industries, but unfortunately at present few data are available. We evaluated the effect of the application of biocontrol products and resistance inducers in the vineyard on the mechanical properties, microbial ecology, technological and phenolic maturity of Vitis vinifera "Nebbiolo" grapes at harvest. The yield and vigor of vines were not influenced by the treatments, nor were the production of primary and secondary metabolites. However, the active ingredients influenced the mechanical properties of the skin (hardness and thickness). A significant hardening of the skin was detected when laminarin and chito-oligosaccharides were used, and sulfur induced a thickening of the skin with potential consequences for wine quality. Furthermore, the yeast community present on grape berries was influenced by the treatments. The abundance of Aureobasidium pullulans, the dominant species on the grape berry, changed in response to the compounds used. In addition, Alternaria sp. was reduced in some treatments with a potentially positive effect on the quality and the safety of the grapes. This study provides an overview of the effect of biocontrol products and resistance inducers on microbial ecology and "Nebbiolo" grape quality, contributing to the establishment of more sustainable and effective defense strategies in viticulture.

Diversity of Saccharomyces cerevisiae yeasts associated to spontaneous and inoculated fermenting grapes from Spanish vineyards

The use of commercial yeast strains is a common practice in winemaking leading to a predictable quality in wine production, avoiding stuck or sluggish fermentations. However, the use of commercial yeasts leads to a consequent reduction in autochthonous microbial diversity. In this study, 1047 isolates from three Spanish appellations of origin were checked for fingerprinting on interdelta polymorphisms and the strain composition and diversity analysed using an extensible open-source platform for processing and analysis of an in-house polymorphism database developed for this study. Ancient vineyards managed with organic practices showed intermediate to low levels of strains diversity indicating the existence of stable populations of Saccharomyces cerevisiae strains. A drastic reduction in the number of different S. cerevisiae strains was observed in vineyards with cellars using a selected autochthonous S. cerevisiae strain for winemaking. Contrary, the use of allochthonous commercial strains in wineries did not seem to affect the native S. cerevisiae strain composition and diversity. SIGNIFICANCE AND IMPACT OF THE STUDY: The aim of this study was to compare different viticulture and oenological practices to determine their influence on the composition and diversity of Saccharomyces cerevisiae strains in wine fermentations. The study shows that the use of autochthonous strains of S. cerevisiae as starters for wine fermentation could have an important incidence on S. cerevisiae strains diversity in surrounding vineyards. The use of autochthonous strains of S. cerevisiae reduced the detected number of S. cerevisiae strains, a fact that was not observed when allochthonous commercial strains were used. Furthermore, vineyards managed with organic practices showed intermediate to low levels of S. cerevisiae strain diversity, whereas conventional practices showed higher levels.