Neža Čadež

The effect of fungicides on yeast communities associated with grape berries

The influence of three commonly used fungicides (iprodione, pyrimethanil and fludioxonil plus cyprodinil) on the density and diversity of yeast populations present on grape berries was evaluated. At the time of harvest, the fungicide residues on grapes were below the maximum permitted levels. In general, larger yeast counts were found on the treated grapes than on the control samples. Among 23 species identified, Cryptococcus magnus, Rhodotorula glutinis and Sporidiobolus pararoseus dominated on sound grape berries. The results showed that the tested fungicides had only a minor impact on the composition of grape berry communities in comparison with the effect of weather conditions and the mode of grape berry sampling. Halo assays using filter discs loaded with fungicides were used as in vitro tests of the sensitivity of grape berry isolates. The fungicide containing pyrimethanil suppressed the growth of all basidiomycetous yeast species, while the sporadically occurring fermentative yeasts were unaffected. Fungicides with fludioxonil plus cyprodinil and iprodione as active substances showed specificity for certain species. Our results suggest that after the safety interval, the presence of fungicides has a minor impact on the composition of grape berry communities, although at the time of fungicide applications, the yeast species composition changes.

Candida adriatica sp. nov. and Candida molendinolei sp. nov., two yeast species isolated from olive oil and its by-products.

Thirteen strains isolated from virgin olive oil or its by-products in several Mediterranean countries were found to be phenotypically and genetically divergent from currently recognized yeast species. Sequence analysis of the large subunit (LSU) rDNA D1/D2 domain and internal transcribed spacer regions/5.8S rDNA revealed that the strains represented two novel species described as Candida adriatica sp. nov. (type strain ZIM 2334(T) = CBS 12504(T) = NCAIM Y.02001(T)) and Candida molendinolei sp. nov. (type strain DBVPG 5508(T) = CBS 12508(T) = NCAIM Y.02000(T)). Phylogenetic analysis based on concatenated sequences of the small subunit rRNA gene, the D1/D2 region of the LSU rDNA and the translation elongation factor-1α gene suggested that C. adriatica sp. nov. and C. molendinolei sp. nov. should be placed within the Lindnera and Nakazawaea clades, respectively.

High genetic similarity of ciprofloxacin-resistant Campylobacter jejuni in central Europe.

Campylobacteriosis is the leading zoonosis in the European Union with the majority of cases attributed to Campylobacter jejuni. Although the disease is usually self-limiting, some severe cases need to be treated with antibiotics, primarily macrolides and quinolones. However, the resistance to the latter is reaching alarming levels in most of the EU countries. To shed light on the expansion of antibiotic resistance in central Europe, we have investigated genetic similarity across 178 ciprofloxacin-resistant C. jejuni mostly isolated in Slovenia, Austria and Germany. We performed comparative genetic similarity analyses using allelic types of seven multilocus sequence typing housekeeping genes, and single nucleotide polymorphisms of a quinolone resistance determining region located within the DNA gyrase subunit A gene. This analysis revealed high genetic similarity of isolates from clonal complex ST-21 that carry gyrA allelic type 1 in all three of these central-European countries, suggesting these ciprofloxacin resistant isolates arose from a recent common ancestor and are spread clonally.

Ogataea kolombanensis sp. nov., Ogataea histrianica sp. nov. and Ogataea deakii sp. nov., three novel yeast species from plant sources

Nine methanol-assimilating yeast strains isolated from olive oil sediments in Slovenia, extra virgin olive oil from Italy and rotten wood collected in Hungary were found to form three genetically separated groups, distinct from the currently recognized yeast species. Sequence analysis from genes of the small subunit (SSU) rRNA, internal transcribed spacer region/5.8S rRNA, large subunit (LSU) rRNA D1/D2 domains and translational elongation factor-1α (EF-1α) revealed that the three closely related groups represent three different undescribed yeast species. Sequence analysis of the LSU rRNA gene D1/D2 domains placed the novel species in the Ogataea clade. The three novel species are designated as Ogataea kolombanensis sp. nov. (type strain: ZIM 2322(T) = CBS 12778(T) = NRRL Y-63657(T)), Ogataea histrianica sp. nov. (type strain: ZIM 2463(T) = CBS 12779(T) = NRRL Y-63658(T)) and Ogataea deakii sp. nov. (type strain: NCAIM Y.01896(T) = CBS 12735(T) = NRRL Y-63656(T)).

The influence of serial repitching of Saccharomyces pastorianus on its karyotype and protein profile during the fermentation of gluten-free buckwheat and quinoa wort

Gluten-free beer-like beverages from malted buckwheat and quinoa are somehow close to their commercial production, but rather high expenses are expected due to the relatively high price of grain, some technological adaptations of process and the need for external enzyme supplementation during mashing. One of the common and efficient cost reduction measures in the industrial scale is serial repitching of the yeast biomass, which has not been studied for the buckwheat and quinoa wort fermentation before. In that manner we have monitored possible changes in yeasts proteins and chromosomal DNA during eleven serial repitchings of the yeast Saccharomyces pastorianus strain TUM 34/70 for fermentation of the barley, buckwheat and quinoa wort. Karyotypes showed changes in regard to the raw materials used and many responsible candidate proteins are suggested which could cause these differences. Different relative expressions of some protein bands were also linked to the proteins involved in yeast stress response and proteins involved in fermentation performance. Results suggest that serial repitching of the strain TUM 34/70 seems suitable for the production of gluten-free beer-like beverages from buckwheat and quinoa.

Population structure and attribution of human clinical Campylobacter jejuni isolates from central Europe to livestock and environmental sources

Campylobacter jejuni is among the most prevalent causes of human bacterial gastroenteritis worldwide. Domesticated animals and, especially, chicken meat are considered to be the main sources of infections. However, the contribution of surface waters and wildlife in C. jejuni transmission to humans is not well understood. We have evaluated the source attribution potential of a six‐gene multiplex PCR (mPCR) method coupled with STRUCTURE analysis on a set of 410 C. jejuni strains isolated from environment, livestock, food and humans in central Europe. Multiplex PCR fingerprints were analysed using Subclade prediction algorithm to classify them into six distinct mPCR clades. A subset of C. jejuni isolates (70%) was characterized by multilocus sequence typing (MLST) demonstrating 74% congruence between mPCR and MLST. The correspondence analysis of mPCR clades and sources of isolation indicated three distinct groups in the studied C. jejuni population—the first one associated with isolates from poultry, the second one with isolates from cattle, and the third one with isolates from the environment. The STRUCTURE analysis attributed 7.2% and 21.7% of human isolates to environmental sources based on MLST and mPCR fingerprints, respectively.

The influence of Dekkera bruxellensis on the transcriptome of Saccharomyces cerevisiae and on the aromatic profile of synthetic wine must

A double compartment membrane system was constructed in order to systematically study possible microbial interactions between yeasts Saccharomyces cerevisiae and Dekkera bruxellensis and their impact on wine aroma. The presence of D. bruxellensis induced 77 transcripts of S. cerevisiae. These were mostly of unknown function; however, some were involved in thiamine biosynthesis and in amino acid and polyamine transport, suggesting a competitive relationship between the two yeast species. Among the transcripts with no biological function, 14 of them were found to be the members of the PAU gene family that is associated with response to anaerobiosis stress. In separated cultures, S. cerevisiae produced glycerol which was subsequently consumed by D. bruxellensis. The concentration of ethylphenols was reduced and we assume that they were absorbed onto the surfaces of S. cerevisiae yeast walls. Also in separated cultures, D. bruxellensis formed a typical profile of aromatic esters with decreased levels of acetate esters and increased level of ethyl esters.

Yeast Habitats: Different but Global

Yeasts, a taxonomically heterogenic group of unicellular fungi, populate many different habitats on our planet. They occur in aquatic and terrestrial environments and also in the atmosphere; however, they are not evenly distributed. While some species are ubiquitous generalists occurring in wide geographic range and dwelling in different habitats, others may have more restricted distribution either geographically or by habitats. Some are known from very few isolates, and about one third of the known yeast species are represented by only one strain. In these cases their ecology remains to be elucidated. As nonmotile organisms their dispersal depends on the vectors carrying them. Insects are of outstanding importance among yeast vectors. Several exciting questions can be raised about the habitat-yeasts-vector associations. For example, which yeasts are there? Why are they only there? How did they get there? What are they doing there?

Census of Yeasts Isolated from Natural Ecosystem and Conserved in Worldwide Collections

There are many well-known public yeast repositories as well as a large number of smaller, less-known collections worldwide; most of these are with the primary goal to preserve the yeast biodiversity in a specific region and the strains from a range of species that are important environmental strains, food spoilage organisms, or strains that play a role in food preparation and human or animal pathogens. In order to have an overview on how many yeast strains are isolated from natural ecosystems and are preserved in collections worldwide, curators of public and private fungal/yeast culture collections were contacted to participate in this survey. Curators of 41 collections from 27 countries supplied data representing a total of 58,095 strains. This includes information on the collection itself, type of environment the strains were isolated from, the countries of origin of the strains, and also the taxonomic information. The ecosystems that are well represented according to the data of preserved strains in the participating collections are plants, insects/invertebrates, aquatic habitats, soil, and extreme cold and extreme warm/dry habitats. The strains have been isolated from a large number of countries worldwide (countries of origin), but it is clear that many parts of the world’s ecosystems are not yet well sampled for yeast diversity. A challenge during this survey was to list the genera and species due to the current and constant changes in taxonomic names. The outcome of this survey is discussed in this chapter.

Kuraishia mediterranea sp. nov., a methanol-assimilating yeast species from olive oil and its sediment

Six yeast strains isolated from olive oil sediments and spoiled olive oils originating from Slovenia and Portugal, respectively, proved to represent an undescribed yeast species based on DNA sequence comparisons. The analysis of gene sequences for internal transcribed spacer regions and the large subunit rRNA gene D1/D2 domain placed the novel species in the genus Kuraishia in a subclade containing Kuraishiacapsulata, the type species of the genus. Although the novel species is well separated genetically from the recognized species of the genus, only a minor phenotypic difference differentiating it from Kuraishia capsulata and K. molischiana was observed. Relevant to its isolation source, no lipolytic activity was detected in the strains of the novel species. To accommodate the above-noted strains, Kuraishia mediterranea sp. nov. (holotype: ZIM 2473T; isotype: CBS 15107T; MycoBank no.: MB 822817) is proposed.