High nitrogen concentration causes G2/M arrest in Hanseniaspora vineae.

Yeasts have been widely used as a model to better understand cell cycle mechanisms and how nutritional and genetic factors can impact cell cycle progression. While nitrogen scarcity is well known to modulate cell cycle progression, the relevance of nitrogen excess for microorganisms has been overlooked. In our previous work, we observed an absence of proper entry into the quiescent state in Hanseniaspora vineae and identified a potential link between this behavior and nitrogen availability. Furthermore, the Hanseniaspora genus has gained attention due to a significant loss of genes associated with DNA repair and cell cycle. Thus, the aim of our study was to investigate the effects of varying nitrogen concentrations on H. vineae's cell cycle progression. Our findings demonstrated that nitrogen excess, regardless of the source, disrupts cell cycle progression and induces G2/M arrest in H. vineae after reaching the stationary phase. Additionally, we observed a viability decline in H. vineae cells in an ammonium-dependent manner, accompanied by increased production of reactive oxygen species, mitochondrial hyperpolarization, intracellular acidification, and DNA fragmentation. Overall, our study highlights the events of the cell cycle arrest in H. vineae induced by nitrogen excess and attempts to elucidate the possible mechanism triggering this absence of proper entry into the quiescent state.

Bacterial community associated with gingivitis and periodontitis in dogs.

Periodontal disease is a chronic condition characterized by bacterial adhesion, followed by biofilm formation, and subsequently by an inflammatory process that progresses to gingivitis and later to periodontitis. The variations in the oral microbiota have been associated with the progression of this disease. This study evaluated the alteration of the cultivable oral microbiota in dogs with different oral health status. Thirty dogs were selected and divided into three groups: healthy, gingivitis, and periodontitis. The collected oral samples were seeded, and colonies with distinct phenotypic characteristics were isolated and classified using sequencing of the 16S rRNA gene. The DNA sequences were aligned, and a phylogenetic tree was constructed. Simpson's diversity index was calculated, and a dissimilarity matrix based on the Jaccard similarity index was used to plot a principal coordinate analysis. A total of 119 bacteria with different colony morphologies were isolated and classified into 4 phyla, 29 genera, and 45 species based on phylogenetic analysis. The results indicated an increase in bacteria belonging to the Proteobacteria phylum and a less extended decrease in Actinobacteria, Firmicutes, and Bacteroidetes phyla in dogs with periodontal disease (gingivitis and periodontitis) compared to healthy dogs. Representatives of the genera Neisseria sp., Corynebacterium sp., Pasteurella sp., and Moraxella sp. increased through the worsening of the periodontal disease, while Staphylococcus sp. decreased. All groups exhibited moderate to high levels of biodiversity index, and the plotted PCoA show a clear separation in the oral microbiome of dogs with periodontitis compared to dogs with gingivitis and the healthy group.

Differences in yeast behaviour during ageing of sparkling wines made with Charmat and Traditional methods.

In this study, we followed the yeast and wine behaviour during the second fermentation and subsequent lees ageing of sparkling wines produced by Traditional and Charmat methods at an industrial scale. During this period, we conducted physicochemical, microbiological, gene expression, and marker analyses of characteristics related to wine ageing. Our results show that the yeast behaviour during the fermentation is similar in both methods. However, after fermentation, there is a faster decrease in yeast vitality and viability in the Charmat method, together with an increase in the expression of autophagy-related genes (AMS1, APE1, and ATG8). We relate these factors to ageing with the continuous homogenization of the liquid practised in the Charmat method, and static ageing with the lees concentrated at the bottom of the bottle performed in the Traditional method. Despite the variation in yeast viability during ageing, there are no differences in soluble proteins, free amino nitrogen, total phenols, antioxidant activity, and colour evolution between the wines produced by the two methods, assuming few differences over the time that monitoring was conducted.

A peculiar cell cycle arrest at g2/m stage during the stationary phase of growth in the wine yeast Hanseniaspora vineae.

Yeasts of the genus Hanseniaspora gained notoriety in the last years due to their contribution to wine quality, and their loss of several genes, mainly related to DNA repair and cell cycle processes. Based on genomic data from many members of this genus, they have been classified in two well defined clades: the "faster-evolving linage" (FEL) and the "slower-evolving lineage" (SEL). In this context, we had detected that H. vineae exhibited a rapid loss of cell viability in some conditions during the stationary phase compared to H. uvarum and S. cerevisiae. The present work aimed to evaluate the viability and cell cycle progression of representatives of Hanseniaspora species along their growth in an aerobic and discontinuous system. Cell growth, viability and DNA content were determined by turbidity, Trypan Blue staining, and flow cytometry, respectively. Results showed that H. uvarum and H. opuntiae (representing FEL group), and H. osmophila (SEL group) exhibited a typical G1/G0 (1C DNA) arrest during the stationary phase, as S. cerevisiae. Conversely, the three strains studied here of H. vineae (SEL group) arrested at G2/M stages of cell cycle (2C DNA), and lost viability rapidly when enter the stationary phase. These results showed that H. vineae have a unique cell cycle behavior that will contribute as a new eukaryotic model for future studies of genetic determinants of yeast cell cycle control and progression.

Aromatic and sensorial characterization of "Moscato pyments": an innovative beverage.

Pyment is a type of mead that is produced from the alcoholic fermentation of a honey solution with the addition of grape juice. Due to the demand for new beverages, pyment can be a profitable alternative for both grape and honey producers. Therefore, this work aimed to characterize the aromatic and physicochemical composition of pyments. The pyments were prepared with addition of 10, 20 and 30% of Moscato juice, and compared with Moscato wine and traditional mead. The results showed an increase in the fermentation rates of Moscato-pyments, indicating that the addition of Moscato juice reverses the low fermentative vigor often reported in mead fermentations. Physicochemical parameters showed an increase in total acidity and a decrease in residual sugar and alcohol, depending on Moscato juice concentration. Moscato-pyments showed an intermediate concentration of volatile compounds between the traditional mead and Moscato wine, with a better balance between fruity, floral and buttery, manifesting characteristic aromas of wines made with Moscato grapes and simultaneously, exposing characteristic aromas of honey. The sensory analysis reveals a significant difference between mead, pyments and Moscato wine. In general, pyments were considered, by the panelists, as the most equilibrated with intermediary aroma intensity, floral, fruity and honey aromas, and good persistence in the mouth.

Yeast biodiversity in honey produced by stingless bees raised in the highlands of southern Brazil.

The physicochemical characteristics and yeasts diversity in honey samples from 17 species of stingless bees of the genera Nannotrigona, Melipona, Plebeia, Scraptotrigona, and Tetragonisca cultivated in Southern Brazil were determined. The sugar content, moisture, water activity, pH, reducing sugars/total sugar ratio, and total yeast population varied significantly among the honey from the different bee species. The highest yeast population was found in the Plebeia's honey samples and correlated with their high water-activity. Sixteen yeast species were identified based on the nuclear large subunit (26S) ribosomal RNA partial sequences. The genera Starmerella and Zygosaccharomyces were found predominant, with a high prevalence of Starmerella sp., S. etchellsii, and S. apicola. Some yeast species were only identified in honey samples from specific bee species indicating a close relationship between the yeasts and the insects. For the first time, Wickerhamomyces sydowiorum in honey is being reported. In general, the yeast species isolated from stingless bee honey samples demonstrated high osmotolerance and low sugar assimilation.

Selection of low nitrogen demand yeast strains and their impact on the physicochemical and volatile composition of mead.

Mead is an ancient alcoholic beverage produced through the fermentation of a diluted solution of honey. Due to the peculiar and varied composition of honey, mead production faces several problems, such as slow or stuck fermentations mainly due to the low nitrogen concentration, lack of uniformity of the final product and the production of unpleasant aromas. In this context, this work aimed to select low nitrogen-demand yeast strains and evaluate their potential for the production of mead. Therefore, among 21 commercial wine yeast strains, 5 were selected based on their fermentative behavior at low assimilable nitrogen concentrations. The selected strains were further evaluated for their contributions in meads produced with limited nitrogen availability, and the results showed significant differences on some physicochemical parameters like biomass production, residual sugars, glycerol concentration, and fermentative rate. Moreover, meads obtained with selected strains differed in the concentration of several volatile compounds. The volatile compounds concentration and the principal component analysis based on odor activity values allowed separating strains into three groups. In general, S. cerevisiae var bayanus strains (QA23, Spark, and AWRI-R2) were the largest producers of aromatic compounds, particularly those with floral and fruity descriptors. The selection of yeast strains with low nitrogen-demand and different volatile compounds production can be explored by mead makers to limit fermentation problems and obtain characteristic products.