Saccharomycetaceae Research Articles

Metagenomic analysis of the microbial community in kefir grains from different milk sources

Abstract. Sumarmono J, Kusuma RJ, Rahayu N, Sukarno AS, Wulansari PD. 2023. Metagenomic analysis of the microbial community in kefir grains from different milk sources. Biodiversitas 24: 5302-5308. Kefir is a type of traditional fermented milk made from kefir grains. The quality of kefir grain depends on the milk medium, which impacts microbial diversity and population. This study uses metagenomic analysis to assess the microbial populations of kefir grains prepared from cow's milk and goat milk using the 16s rRNA method. The results revealed that >99% Relative Abundance (RA) of the sample's total bacteria belonged to the phylum Firmicutes and the phylum Bacteroidota, respectively. However, most of the phylum Firmicutes was found in the sample of goat milk kefir. Further investigation revealed that goat milk samples had Lactobacillus, Streptococcus, and Staphylococcus genera, while the cow milk samples contained >99% RA of Lactobacillus, Bacteroides, and Muribaculaceae. Regarding yeast, the family Saccharomycetaceae predominated in cow's milk, while goat milk had 2% of the family Saccharomycetaceae and 97% of unassigned microorganisms. The functional analysis revealed that kefir grains from the two sources had a variety of amino acid metabolisms, secondary metabolite metabolisms, and vitamin production. This metagenomic analysis shows that the type of milk affects the diversity of the population of both bacteria and yeast. This study opens up opportunities to further investigate the potential of kefir as a functional food beverage, a source of probiotics, and an antibacterial agent property.

Microbiological properties of opportunistic saccharomycetes of the genus <i>Candida</i> in chronic, recurrent infectious inflammatory processes (literature review)

Literature review involves a problem analysis of current scientific publications on yeast-like fungi of the genus Candida of the family Saccharomycetaceae. In 90% of cases, the etiological factor of chronic, recurrent infectious and inflammatory processes is represented by residents of oral, intestinal, urogenital and skin microbiome, opportunistic Candida albicans fungi. The paper considers the relevant medical and social problem of endogenous opportunistic infections on the example of candidiasis (candidamycosis). The review presents a conceptual analysis of changes in the microbiological properties of clinically significant candida species with ubiquitous distribution: Candida albicans, Candida tropicalis, Candida glabrata, Candida krusei, Candida parapsilosis, Candida dubliniensis, Candida auris. The authors provide a current perspective on the risk of superficial and invasive candidomycosis as an opportunistic, non-cyclic infection. Signs of the same type of pathological process develop with the participation of different species of opportunistic fungi in monoculture and associations against the background of immunodeficiency.

Analysis of kefi r grains from diff erent regions of the planet using high-throughput sequencing

The taxonomic composition and spatial localization of yeast and bacteria in kefi r grains (KG) obtained for study from diff erent regions of the planet were investigated. The diversity of their microbiome has been demonstrated by high-throughput sequencing of bacterial 16S rRNA genes and the ITS1 region of the 18S-ITS1-5.8S-ITS2-28S complex of yeast rRNA. It has been established that the main representatives of the complex community of KG from diff erent regions are lactic acid bacteria (LAB; lactobacilli, lactococci and Leuconostoc spp. in diff erent ratios), and diff erent types of yeast of the genus Kazachstania (family Saccharomycetaceae). Acetic acid bacteria and a small percentage of yeast Kluyveromyces marxianus were detected in the KG from Tibet, and yeast Pichia kluyveri was detected in the KG from Ossetia.

Analysis of Kefir Grains from Different Regions of the Planet Using High-Throughput Sequencing.

The taxonomic composition and spatial localization of yeast and bacteria in kefir grains (KG) obtained for study from different regions of the planet were investigated. The diversity of their microbiome has been demonstrated by high-throughput sequencing of bacterial 16S rRNA genes and the ITS1 region of the 18S-ITS1-5.8S-ITS2-28S complex of yeast rRNA. It has been established that the main representatives of the complex community of KG from different regions are lactic acid bacteria (LAB; lactobacilli, lactococci, and Leuconostoc spp. in different ratios) and different types of yeast of the genus Kazachstania (family Saccharomycetaceae). Acetic acid bacteria and a small percentage of yeast Kluyveromyces marxianus were detected in the KG from Tibet, and yeast Pichia kluyveri was detected in the KG from Ossetia.

Structure of the pre-mRNA leakage 39-kDa protein reveals a single domain of integrated zf-C3HC and Rsm1 modules

In Saccharomyces cerevisiae, the pre-mRNA leakage 39-kDa protein (ScPml39) was reported to retain unspliced pre-mRNA prior to export through nuclear pore complexes (NPCs). Pml39 homologs outside the Saccharomycetaceae family are currently unknown, and mechanistic insight into Pml39 function is lacking. Here we determined the crystal structure of ScPml39 at 2.5 Å resolution to facilitate the discovery of orthologs beyond Saccharomycetaceae, e.g. in Schizosaccharomyces pombe or human. The crystal structure revealed integrated zf-C3HC and Rsm1 modules, which are tightly associated through a hydrophobic interface to form a single domain. Both zf-C3HC and Rsm1 modules belong to the Zn-containing BIR (Baculovirus IAP repeat)-like super family, with key residues of the canonical BIR domain being conserved. Features unique to the Pml39 modules refer to the spacing between the Zn-coordinating residues, giving rise to a substantially tilted helix αC in the zf-C3HC and Rsm1 modules, and an extra helix αAB′ in the Rsm1 module. Conservation of key residues responsible for its distinct features identifies S. pombe Rsm1 and Homo sapiens NIPA/ZC3HC1 as structural orthologs of ScPml39. Based on the recent functional characterization of NIPA/ZC3HC1 as a scaffold protein that stabilizes the nuclear basket of the NPC, our data suggest an analogous function of ScPml39 in S. cerevisiae.

Kazachstania humilis.

Kazachstania humilis is an ascomycetous budding yeast from the family Saccharomycetaceae and is best known as a fermenting yeast in wheat and rye sourdoughs. It is the second most commonly identified sourdough yeast after Saccharomyces cerevisiae. Seven species of Kazachstania yeasts (including K. humilis) have been isolated from sourdoughs, making it the best represented yeast genus in this environment. Furthermore, sourdoughs from every continent have been found to contain K. humilis.

P330 Role of a D-amino acid oxidase (DAO) in an efficient human commensal Candida albicans

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PM Objectives Candida albicans is an opportunistic fungal pathogen residing as a harmless commensal component of the human microbiota. In the gut, C. albicans efficiently colonizes and successfully competes to limiting nutrient resources and overcomes the detrimental effect of an array of secondary metabolites released by the host and the dominant bacterial microflora. Among the metabolites, several free D-amino acids are released into the gut lumen, especially as a result of the degradation of bacterial cell walls. We sought to identify the genes that might confer advantages to C. albicans in metabolizing D-amino acids in diverse morphotypes, which might confer a competitive advantage.MethodsAll C. albicans genetically modified strains were constructed using a standard lithium acetate transformation method. The D-amino acid utilization and growth of C. albicans strains were assessed by spot dilution assays on minimal media agar plates at 30°C. Morphological switching between the yeast and hyphal forms was assessed in liquid media using hyphal-inducing conditions in the presence or absence of D-amino acids. Biofilm assays were performed using YNB-galactose media (with or without D-amino acids) on serum-treated 6-well plates at 30°C.Results C. albicans genome harbors three ORFs putatively encoding D-amino acid oxidase genes- DAO1orf19.3065, DAO2orf3365, and IFG3orf19.944. D-amino oxidase genes are lost from the genomes of several fungal species belonging to the Saccharomycetaceae family, including the free-living Saccharomyces cerevisiae. We found that C. albicans utilizes and grows on D-leucine, an amino acid known to be released by the gut bacteria into the intestinal lumen. This utilization is dependent on the growth morphotypes since the cells growing in biofilm fail to metabolize D-leucine. However, deletion of IFG3 but neither DAO1 nor DAO2 completely abrogates D-leucine utilization capabilities of C. albicans. The null ifg3 strain is moderately growth-sensitive in presence of D-alanine, an amino acid abundantly present and synthesized in the gut by bacteria for incorporation into peptidoglycan in their cell walls. By comparing Ifg3 protein levels in a leucine auxotrophic strain in different growth modes, we found that the expression of Ifg3 protein increases several folds in the biofilm growth mode in presence of D-leucine, but cells fail to grow optimally and make three-dimensional biofilm. Furthermore, ectopic expression of CaIFG3 in S. cerevisiae, which lost all D-amino oxidase genes, helps the organism to utilize D-leucine as a nutrient resource as well as overcome its inhibitory effect on growth.ConclusionOur results indicate that Ifg3 provides C. albicans the ability to metabolize D-leucine and helps it to overcome the growth inhibitory effect of D-alanine. Based on these primary observations we speculate a crucial role of Ifg3 in providing a competitive advantage against the resident microflora in the gut where continuous turnover of D-amino acids is crucial in maintaining host-microbe symbiotic interactions. Further in vivo commensalism experiments in mice will provide important clues on the role of this enzyme in C. albicans’s ability in gut colonization.

Coinfection with Sars-Cov2 and Kodamaea ohmeri: A case report from Tunisia

Introduction: Kodamaea ohmeri, previously known as Yamadazyma ohmeri and Pichia ohmeri, is ascomycetous yeast that belongs to the Saccharomycetaceae family. It is a rare clinical isolate that has recently become known to cause various human infections. Here, we report the first case of co-infection with Sars-Cov2 and Kodamaea ohmeri in Tunisian patient without underlying disease. Methodology: We describe a patient with Covid-19 where Kodamaea ohmeri was isolated in sputum and protected tracheal samples. The identification was carried out by Vitek®2 YST ID card and confirmed by PCR sequencing. Susceptibility to antifungal was made by E-test. Results: Kodamaea ohmeri was identified using phenotypic, biochemical, and molecular methods. The isolate was susceptible for amphotericin B, caspofungin, and intermediate sensitivity for Fluconazole. Conclusion: Patients with severe Covid-19 are mostly colonized and co-infected with rare yeasts which are resistant to antifungals. This case incites to pay more attention to the emergence of this yeast. Keywords: Kodamaea ohmeri; diagnosis; antifungal; molecular methods.

Candida glabrata Hst1-Rfm1-Sum1 complex evolved to control virulence-related genes

C. glabrata is an opportunistic fungal pathogen and the second most common cause of opportunistic fungal infections in humans, that has evolved virulence factors to become a successful pathogen: strong resistance to oxidative stress, capable to adhere and form biofilms in human epithelial cells as well as to abiotic surfaces and high resistance to xenobiotics. Hst1 (a NAD+-dependent histone deacetylase), Sum1 (putative DNA binding protein) and Rfm1 (connector protein) form a complex (HRS-C) and control the resistance to oxidative stress, to xenobiotics (the antifungal fluconazole), and adherence to epithelial cells. Hst1 is functionally conserved within the Saccharomycetaceae family, Rfm1 shows a close phylogenetic relation within the Saccharomycetaceae family while Sum1 displays a distant phylogenetic relation with members of the family and is not conserved functionally. CDR1 encodes for an ABC transporter (resistance to fluconazole) negatively controlled by HRS-C, for which its binding site is located within 223 bp upstream from the ATG of CDR1. The absence of Hst1 and Sum1 renders the cells hyper-adherent, possibly due to the overexpression of AED1, EPA1, EPA22 and EPA6, all encoding for adhesins. Finally, in a neutrophil survival assay, HST1 and SUM1, are not required for survival. We propose that Sum1 in the HRS-C diverged functionally to control a set of genes implicated in virulence: adherence, resistance to xenobiotics and oxidative stress.

INFLUENCE OF HYDROLYTIC TREATMENT ON THE CONTENT OF REDUCING SUBSTANCES IN NEUTRAL-SULPHITE ALKALI

The aim of this work is to develop a technology for the preparation of neutral-sulfite liquors formed during the production of fibrous semi-finished products - cellulose from birch wood - for subsequent use as a nutrient medium for the cultivation of microorganisms. Acid hydrolysis was carried out at a temperature of 100 °С at a ratio of a 10% sulfuric acid solution to a liquor sample of 1 : 1. Enzymatic hydrolysis of neutral sulfite liquors was carried out with the enzyme preparations Accellerase XY and Accellerase XC at 50±2 °C and 60±2 °C. The end of hydrolysis was determined by the cessation of the increase in the content of reducing substances (RS) in the hydrolyzate. The original neutral sulphite lye contained 9.4% dry matter, 21.7 g/l of reducing substances, pH 5.3±0.2. It has been shown that as a result of enzymatic hydrolysis, the content of insoluble dry residue in the hydrolyzate decreases to 8.32% and 8.41%, respectively, and during acid hydrolysis – to 7.8%. The content of RS in neutral sulfite lye after acid hydrolysis increases by an average of 3 times, while after enzymatic hydrolysis - a maximum of 2 times. It was found by gas-liquid chromatography that pentoses predominate in the obtained hydrolysates. Microbiological processing of media with a similar carbohydrate composition is possible by a number of strains of microorganisms capable of assimilating pentoses, for example, yeast-like fungi of the Saccharomycetaceae family and bacteria of the Enterobacteriaceae family.

Role of Yeasts in the Cranberry Fruit Rot Disease Complex.

Cranberry fruit rot (CFR) is an economically important disease caused by at least 10 species of filamentous fungi. Despite the application of fungicides, incidence of CFR is sometimes high, raising the possibility of a role for microbes other than fungi in the CFR complex. Isolation of microbes from rotten berries on culture media that favor either bacteria or yeasts resulted in mucoid colonies from <15% of dry-harvested rotten berries but up to 60% of wet-harvested berries. The mucoid colonies were identified as yeasts, primarily in the family Saccharomycetaceae. Inoculation of sound berries with three yeasts, Hanseniaspora uvarum, Pichia fermentans, and Pichia terricola, resulted in significantly higher incidence and severity of rot symptoms compared with mock-inoculated controls; these yeasts were recovered from inoculated berries, providing evidence of their pathogenicity. The minimum concentrations of azoxystrobin, chlorothalonil, and prothioconazole that resulted in 80% inhibition of growth compared with untreated controls (MIC80) were determined for a subset of yeasts. In general, MIC80s were higher for azoxystrobin and prothioconazole (usually >64 µg/ml) than for chlorothalonil (usually ≤1 µg/ml). To complement culture-dependent studies, DNA was isolated from wet- and dry-harvested rotten berries, and fungi were identified to the level of family by high-throughput sequencing of the fungal internal transcribed spacer region. There were no fungal families consistently detected among samples by one method (culturing or high-throughput sequencing) and missed by the other that have not previously been reported in cranberry; however, some fungal families were found to be more abundant by one method versus the other. Harvest method (wet or dry) had a significant effect on the composition of fungal communities of rotten berries (P < 0.001), and operational taxonomic units representing the Saccharomycetaceae were more abundant in wet- than dry-harvested berries. Taken together, the results suggest that some yeasts are pathogenic to cranberry and may be especially relevant in wet-harvested berries.

Signatures of optimal codon usage in metabolic genes inform budding yeast ecology.

Reverse ecology is the inference of ecological information from patterns of genomic variation. One rich, heretofore underutilized, source of ecologically relevant genomic information is codon optimality or adaptation. Bias toward codons that match the tRNA pool is robustly associated with high gene expression in diverse organisms, suggesting that codon optimization could be used in a reverse ecology framework to identify highly expressed, ecologically relevant genes. To test this hypothesis, we examined the relationship between optimal codon usage in the classic galactose metabolism (GAL) pathway and known ecological niches for 329 species of budding yeasts, a diverse subphylum of fungi. We find that optimal codon usage in the GAL pathway is positively correlated with quantitative growth on galactose, suggesting that GAL codon optimization reflects increased capacity to grow on galactose. Optimal codon usage in the GAL pathway is also positively correlated with human-associated ecological niches in yeasts of the CUG-Ser1 clade and with dairy-associated ecological niches in the family Saccharomycetaceae. For example, optimal codon usage of GAL genes is greater than 85% of all genes in the genome of the major human pathogen Candida albicans (CUG-Ser1 clade) and greater than 75% of genes in the genome of the dairy yeast Kluyveromyces lactis (family Saccharomycetaceae). We further find a correlation between optimization in the GALactose pathway genes and several genes associated with nutrient sensing and metabolism. This work suggests that codon optimization harbors information about the metabolic ecology of microbial eukaryotes. This information may be particularly useful for studying fungal dark matter-species that have yet to be cultured in the lab or have only been identified by genomic material.

Postzygotic reproductive isolation among three Saccharomyces yeast species.

We have previously isolated heterothallic haploid strains from original homothallic diploids of two yeast species in the family Saccharomycetaceae. In this study, heterothallic haploid strains were isolated from an original homothallic diploid of Saccharomyces kudriavzevii type strain, followed by investigation of sexual interactions among these yeast strains, in addition to S. cerevisiae laboratory strains. It has been shown that prezygotic reproductive isolation was observed between Kazachstania naganishii and S. cerevisiae with α-factor mating pheromones representing crossaction with each other beyond the genus boundary. Using heterothallic strains, postzygotic reproductive isolation system was shown to reside in the genus Saccharomyces by mass mating and cell-cell contact experiments. In mass mating experiments, crossaction of α-factor and a-factor mating pheromones and sexual agglutination effectively occurred beyond species boundaries among S. kudriavzevii, S. paradoxus, and S. cerevisiae. When the fates of cell-cell pairs from these Saccharomyces yeast species were systematically chased one by one, interspecific F1 hybrids were effectively produced, while sporulations were partially prohibited, with spore germination perfectly blocked in the hybrids. These results indicated that postzygotic reproductive isolation definitively resides among these Saccharomyces yeast species and that disorder of chromosome organization had to some extent occurred in interspecific F1 hybrids.

Metabolic cooperation and spatiotemporal niche partitioning in a kefir microbial community.

Microbial communities often undergo intricate compositional changes yet also maintain stable coexistence of diverse species. The mechanisms underlying long-term coexistence remain unclear as system-wide studies have been largely limited to engineered communities, ex situ adapted cultures, or synthetic assemblies. Here we show how kefir, a natural milk-fermenting community of prokaryotes (predominantly lactic and acetic acid bacteria) and yeasts (family Saccharomycetaceae), realizes stable coexistence through spatiotemporal orchestration of species and metabolite dynamics. During milk fermentation, kefir grains (a polysaccharide matrix synthesized by kefir microbes) grow in mass but remain unchanged in composition. In contrast, the milk is colonized in a sequential manner in which early members open the niche for the followers by making available metabolites like amino acids and lactate. Through metabolomics, transcriptomics and large-scale mapping of inter-species interactions, we show how microbes poorly suited for milk survive in — and even dominate — the community, through metabolic cooperation and uneven partitioning between grain and milk. Overall, our findings reveal how inter-species interactions partitioned in space and time lead to stable coexistence.

The Effect of Chalcones and Flavanones on Zymase Fermentation of Saccharomyces cerevisiae

The biological activity of seven chalcones and six flavanones in yeasts of the Saccharomycetaceae family has been investigated. It has been shown that 2',4'-dihydroxychalcone, 2',4'-dihydroxy-5'-ethylchalcone, 7-hydroxy-6-ethylflavanone, 7-hydroxy-6-n-hexylflavanone, 7-methoxy-6-tert-butylflavanone at a concentration of 50...100 μmol/l suppresses the metabolism of the yeast cell and reduces the zymase fermentation of Saccharomyces cerevisiae. It was found that the investigated flavanomes have no biological activity in relation to Candida albicans.

Savitreea pentosicarens gen. nov., sp. nov., a yeast species in the family Saccharomycetaceae isolated from a grease trap.

Two strains (DMKU-GTCP10-8 and CLIB 1740) representing a novel anamorphic yeast species were isolated from a grease sample collected from a grease trap in Thailand and from an unidentified fungus collected in French Guiana, respectively. On the basis of phylogenetic analysis based on the combined D1/D2 domain of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) region, Lachancea fermentati CBS 707T was the closely related species with 12.8 % sequence divergence (70 nucleotide substitutions and three gaps in 571 nucleotides) and 28.1 % sequence divergence (93 nucleotide substitutions and 90 gaps in 651 nucleotides) in the D1/D2 domain of the LSU rRNA gene and the ITS region, respectively. Phylogenetic analysis based on the concatenated sequences of the five genes including the small subunit rRNA gene, the D1/D2 domain of the LSU rRNA gene, the ITS region, translation elongation factor-1 alpha (TEF1) and RNA polymerase II subunit 2 (RPB2) genes confirmed that the two strains (DMKU-GTCP10-8 and CLIB 1740) were well-separated from other described yeast genera in Saccharomycetaceae. Hence, Savitreea pentosicarens gen. nov., sp. nov. is proposed to accommodate these two strains as members of the family Saccharomycetaceae. The holotype is S. pentosicarens DMKU-GTCP10-8T (ex-type strain TBRC 12159=PYCC 8490; MycoBank number 835044).

Kodamaea ohmeri infections in humans: A systematic review.

Kodamaea ohmeri, previously known as Pichia ohmeri or Yamadazyma ohmeri, belongs to the Saccharomycetaceae family and the Ascomycetae class, is the telomorphic form of Cguilliermondii var. membranaefaciens and is frequently mistaken for Candida, as they belong to the same family. It has been isolated from environmental sources, such as sand, pools, seawater and fruits, while the last decades it is recognised as a rare pathogen that causes life-threatening infections in humans. The purpose of this study was to systemically review all published cases of Kohmeri infections in the literature and describe the epidemiology, microbiology, antimicrobial susceptibility, treatment and outcomes of these infections in humans. Systematic review of PubMed (through 27th December 2019) for studies providing epidemiological, clinical, microbiological as well as treatment data and outcomes of Kohmeri infections. A total of 35 studies, containing data of 44 patients, were included in the analysis. The most common Kohmeri infections were those of the bloodstream, infective endocarditis and onychomycosis. Previous antibiotic use, presence of a central venous catheter, parenteral nutrition and cancer were very common among patients. Mortality was high in the case of fungemias but low for other types of infections. Amphotericin B and fluconazole are the most common agents used for treatment, even though alarming MICs for fluconazole were noted. This systematic review thoroughly describes infections by Kohmeri and provides information on their epidemiology, clinical presentation, microbiology, antibiotic resistance patterns, treatment and outcomes.

A white-to-opaque-like phenotypic switch in the yeast Torulaspora microellipsoides

Torulaspora microellipsoides is an under-characterized budding yeast of the Saccharomycetaceae family that is primarily associated with viticulture. Here we report for the first time to our knowledge that T. microellipsoides undergoes a low-frequency morphological switch from small budding haploid (white) yeast to larger, higher ploidy (opaque) yeast. Comparison of transcriptomes by mRNA-seq revealed 511 differentially regulated genes, with white cells having greater expression of genes involved in stress resistance and complex carbohydrate utilization, and opaque cells up-regulating genes involved in ribosome biogenesis. Growth assays showed that white cells are physiologically more resistant to stationary-phase conditions and oxidative stress, whereas opaque cells exhibited greater cold tolerance. We propose that phenotypic switching in T. microellipsoides is an ecological adaptation, as has been suggested for similar morphological switching in distantly related species like Candida albicans, and we propose that this switching is a more broadly utilized biological strategy among yeasts than previously thought.

In situ Linkage of Fungal and Bacterial Proliferation to Microbiologically Influenced Corrosion in B20 Biodiesel Storage Tanks.

Renewable fuels hold great promise for the future yet their susceptibility to biodegradation and subsequent corrosion represents a challenge that needs to be directly assessed. Biodiesel is a renewable fuel that is widely used as a substitute or extender for petroleum diesel and is composed of a mixture of fatty acid methyl esters derived from plant or animal fats. Biodiesel can be blended up to 20% v/v with ultra-low sulfur diesel (i.e., B20) and used interchangeably with diesel engines and infrastructure. The addition of biodiesel, however, has been linked to increased susceptibility to biodegradation. Microorganisms proliferating via degradation of biodiesel blends have been linked to microbiologically influenced corrosion in the laboratory, but not measured directly in storage tanks (i.e., in situ). To measure in situ microbial proliferation, fuel degradation and microbially influenced corrosion, we conducted a yearlong study of B20 storage tanks in operation at two locations, identified the microorganisms associated with fuel fouling, and measured in situ corrosion. The bacterial populations were more diverse than the fungal populations, and largely unique to each location. The bacterial populations included members of the Acetobacteraceae, Clostridiaceae, and Proteobacteria. The abundant Eukaryotes at both locations consisted of the same taxa, including a filamentous fungus within the family Trichocomaceae, not yet widely recognized as a contaminant of petroleum fuels, and the Saccharomycetaceae family of yeasts. Increases in the absolute and relative abundances of the Trichocomaceae were correlated with significant, visible fouling and pitting corrosion. This study identified the relationship between fouling of B20 with increased rates of corrosion and the microorganisms responsible, largely at the bottom of the sampled storage tanks. To our knowledge this is the first in situ study of this scale incorporating community and corrosion measurements in an active biodiesel storage environment.

Looking at the Origin: Some Insights into the General and Fermentative Microbiota of Vineyard Soils

In winemaking processes, there is a current tendency to develop spontaneous fermentations taking advantage of the metabolic diversity of derived from the great microbial diversity present in grape musts. This enological practice enhances wine complexity, but undesirable consequences or deviations could appear on wine quality. Soil is a reservoir of important microorganisms for different beneficial processes, especially for plant nutrition, but it is also the origin of many of the phytopathogenic microorganisms that affect vines. In this study, a meta-taxonomic analysis of the microbial communities inhabiting vineyard soils was realized. A significant impact of the soil type and climate aspects (seasonal patterns) was observed in terms of alpha and beta bacterial diversity, but fungal populations appeared as more stable communities in vineyard soils, especially in terms of alpha diversity. Focusing on the presence and abundance of wine-related microorganisms present in the studied soils, some seasonal and soil-dependent patterns were observed. The Lactobacillaceae family, containing species responsible for the malolactic fermentation, was only present in non-calcareous soils samples and during the summer season. The study of wine-related fungi indicated that the Debaryomycetaceae family dominates the winter yeast population, whereas the Saccharomycetaceae family, containing the most important fermentative yeast species for winemaking, was detected as dominant in summer.