Regulatory Oversight and Safety of Probiotic Use

Saccharomyces boulardii probiotics should be used with caution for management of Clostridium difficile infections in hospitalized patients

The Rewiring of Ubiquitination Targets in a Pathogenic Yeast Promotes Metabolic Flexibility, Host Colonization and Virulence

Funding: This work was funded by the European Research Council [http://erc.europa.eu/], AJPB (STRIFE Advanced Grant; C-2009-AdG-249793). The work was also supported by: the Wellcome Trust [www.wellcome.ac.uk], AJPB (080088, 097377); the UK Biotechnology and Biological Research Council [www.bbsrc.ac.uk], AJPB (BB/F00513X/1, BB/K017365/1); the CNPq-Brazil [http://cnpq.br], GMA (Science without Borders fellowship 202976/2014-9); and the National Centre for the Replacement, Refinement and Reduction of Animals in Research [www.nc3rs.org.uk], DMM (NC/K000306/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Acknowledgments We thank Dr. Elizabeth Johnson (Mycology Reference Laboratory, Bristol) for providing strains, and the Aberdeen Proteomics facility for the biotyping of S. cerevisiae clinical isolates, and to Euroscarf for providing S. cerevisiae strains and plasmids. We are grateful to our Microscopy Facility in the Institute of Medical Sciences for their expert help with the electron microscopy, and to our friends in the Aberdeen Fungal Group for insightful discussions.Peer reviewedPublisher PD

Saccharomyces cerevisiae: Population Divergence and Resistance to Oxidative Stress in Clinical, Domesticated and Wild Isolates

BACKGROUND: Saccharomyces cerevisiae has been associated with human life for millennia in the brewery and bakery. Recently it has been recognized as an emerging opportunistic pathogen. To study the evolutionary history of S. cerevisiae, the origin of clinical isolates and the importance of a virulence-associated trait, population genetics and phenotypic assays have been applied to an ecologically diverse set of 103 strains isolated from clinics, breweries, vineyards, fruits, soil, commercial supplements and insect guts. METHODOLOGY/PRINCIPAL FINDINGS: DNA sequence data from five nuclear DNA loci were analyzed for population structure and haplotype distribution. Additionally, all strains were tested for survival of oxidative stress, a trait associated with microbial pathogenicity. DNA sequence analyses identified three genetic subgroups within the recombining S. cerevisiae strains that are associated with ecology, geography and virulence. Shared alleles suggest that the clinical isolates contain genetic contribution from the fruit isolates. Clinical and fruit isolates exhibit high levels of recombination, unlike the genetically homogenous soil isolates in which no recombination was detected. However, clinical and soil isolates were more resistant to oxidative stress than any other population, suggesting a correlation between survival in oxidative stress and yeast pathogenicity. CONCLUSIONS/SIGNIFICANCE: Population genetic analyses of S. cerevisiae delineated three distinct groups, comprising primarily the (i) human-associated brewery and vineyard strains, (ii) clinical and fruit isolates (iii) and wild soil isolates from eastern U.S. The interactions between S. cerevisiae and humans potentiate yeast evolution and the development of genetically, ecologically and geographically divergent groups

N-Alkylated Linear Heptamethine Polyenes as Potent Non-Azole Leads against Candida Albicans Fungal Infections

In this study, eighteen heptamethine dyes were synthesised and their antifungal activities were evaluated against three clinically relevant yeast species.. The eighteen dyes were placed within classes based on their core subunit i.e. 2,3,3-trimethylindolenine (5a-f), 1,1,2-trimethyl-1H-benzo[e]indole (6a-f), or 2-methylbenzothiazole (7a-f). The results presented herein imply that the three families of cyanine dyes, in particular compounds 5a-f, show high potential as selective scaffolds to treat C. albicans infections. This opens up the opportunity for further optimisation and investigation of this class compounds for potential antifungal treatment

Expression variability of co-regulated genes differentiates Saccharomyces cerevisiae strains

Background: Saccharomyces cerevisiae (Baker’s yeast) is found in diverse ecological niches and is characterized by high adaptive potential under challenging environments. In spite of recent advances on the study of yeast genome diversity, little is known about the underlying gene expression plasticity. In order to shed new light onto this biological question, we have compared transcriptome profiles of five environmental isolates, clinical and laboratorial strains at different time points of fermentation in synthetic must medium, during exponential and stationary growth phases. Results: Our data unveiled diversity in both intensity and timing of gene expression. Genes involved in glucose metabolism and in the stress response elicited during fermentation were among the most variable. This gene expression diversity increased at the onset of stationary phase (diauxic shift). Environmental isolates showed lower average transcript abundance of genes involved in the stress response, assimilation of nitrogen and vitamins, and sulphur metabolism, than other strains. Nitrogen metabolism genes showed significant variation in expression among the environmental isolates. Conclusions: Wild type yeast strains respond differentially to the stress imposed by nutrient depletion, ethanol accumulation and cell density increase, during fermentation of glucose in synthetic must medium. Our results support previous data showing that gene expression variability is a source of phenotypic diversity among closely related organisms.Fundação para a Ciência e TecnologiaThe authors wish to thank Adega Cooperativa da Bairrada, Cantanhede, Portugal, for providing the commercial strains

Candida glabrata (pathogène fongique émergent)

Candida glabrata est le second agent étiologique des candidoses de l'adulte. Nous avons développé une PCR pour le différentier de C. bracarensis et C. nivariensis deux espèces phénotypiquement identiques. Le développement d une méthode de typage par microsatellites, nous a permis de montrer une répartition des souches principalement au sein de six complexes clonaux, l un ne comportant que des souches MATa. La méthode a été validée pour le traçage des souches. L analyse des génotypes de souches isolées du tube digestif humain et d hémocultures a montré que C. glabrata pouvait micro-évoluer au niveau du tube digestif, qu une transmission intrafamiliale existait et que les souches digestives présentaient une diversité génétique plus importante. Celle-ci a été aussi retrouvée par l analyse du polymorphisme de taille des gènes EPA. Nous avons étudié comparativement l adhésion in vitro sur cellules Caco2, de souches présentant des génotypes différents. Le niveau d adhésion n était pas corrélé aux caractéristiques génétiques mais il existait d importantes variations selon les souches. Ces résultats devraient être utiles pour des études ultérieuresPARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Neospora caninum (à propos d'une étude sérologique chez des patients infectés par le VIH)

PARIS6-Bibl. St Antoine CHU (751122104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Genome editing in the yeast Nakaseomyces delphensis and description of its complete sexual cycle

The environmental yeast Nakaseomyces delphensis is, phylogenetically, the closest known species to Candida glabrata, a major fungal pathogen of humans. C. glabrata is haploid and described as asexual, while N. delphensis is also haploid, but has been described as competent for mating and meiosis. Both genomes contain homologs of all the genes necessary for sexual reproduction, and also the genes for Ho-dependent mating-type switching, like Saccharomyces cerevisiae. We first report the construction of genetically-engineered strains of N. delphensis, including by CRISPR-Cas 9 gene-editing. We also report the description of the sexual cycle of N. delphensis. We show that it undergoes Ho-dependent mating-type switching in culture, and that deletion of the HO gene prevents such switching and allows maintenance of stable, separate, MATa and MATalpha haploid strains. Rare, genetically selected diploids can be obtained through mating of haploid strains, mutated or not for the HO gene. In contrast to HO/HO diploids, which behave as expected, Δho/Δho diploids exhibit unusual profiles in flow-cytometry. Both types of diploids can produce recombined haploid cells, which grow like the original haploid type strain. Our experiments thus allow the genetic manipulation of N. delphensis and the reconstruction, in the laboratory, of its entire life-cycle