Does Aqueous Fullerene Inhibit the Growth of Saccharomyces cerevisiae or Escherichia coli?

Studies reporting on potentially toxic interactions between aqueous fullerene nanoparticles (nC₆₀) and microorganisms have been contradictory. When known confounding factors were avoided, growth yields of Saccharomyces cerevisiae and Escherichia coli cultured in the presence and absence of independently prepared lots of underivatized nC₆₀ were found not to be significantly different.This is the publisher’s final pdf. The published article is copyrighted by the American Society for Microbiology and can be found at: http://aem.highwire.org/

Identification of gold nanoparticle-resistant mutants of Saccharomyces cerevisiae suggests a role for respiratory metabolism in mediating toxicity

Positively-charged gold nanoparticles (0.8-nm core diameter) reduced yeast survival, but not growth, at a concentration of 10 to 100 μg/ml. Among 17 resistant deletion mutants isolated in a genome-wide screen, highly significant enrichment was observed for respiration-deficient mutants lacking genes encoding proteins associated with the mitochondrion

De novo synthesis of a sunscreen compound in vertebrates

Ultraviolet-protective compounds, such as mycosporine-like amino acids (MAAs) and related gadusols produced by some bacteria, fungi, algae, and marine invertebrates, are critical for the survival of reef-building corals and other marine organisms exposed to high-solar irradiance. These compounds have also been found in marine fish, where their accumulation is thought to be of dietary or symbiont origin. In this study, we report the unexpected discovery that fish can synthesize gadusol de novo and that the analogous pathways are also present in amphibians, reptiles, and birds. Furthermore, we demonstrate that engineered yeast containing the fish genes can produce and secrete gadusol. The discovery of the gadusol pathway in vertebrates provides a platform for understanding its role in these animals, and the possibility of engineering yeast to efficiently produce a natural sunscreen and antioxidant presents an avenue for its large-scale production for possible use in pharmaceuticals and cosmetics.This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by eLife Sciences Publications. The published article can be found at: http://elifesciences.org/Supporting information can be found at: http://elifesciences.org/content/4/e0591

Conversion of Wine Strains of Saccharomyces cerevisiae to Heterothallism

A general method to convert homothallic strains of the yeast Saccharomyces cerevisiae to heterothallism is described which is applicable to genetically well-behaved diploids, as well as to strains that sporulate poorly or produce few viable and mating-competent spores. The heterothallic (ho) allele was introduced into three widely used wine strains through spore × cell hybridization. The resultant hybrids were sporulated, and heterothallic segregants were isolated for use in successive backcrosses. Heterothallic progeny of opposite mating type and monosomic for chromosome III produced by sixth-backcross hybrids or their progeny were mated together to reconstruct heterothallic derivatives of the wine strain parents. A helpful prerequisite to the introduction of ho was genetic purification of the parental strains based on repeated cycles of sporulation, ascus dissection, and clonal selection. A positive selection to isolate laboratory-wine strain hybrids requiring no prior genetic alteration of the industrial strains, coupled with a partial selection to reduce the number of spore progeny needed to be screened to isolate heterothallic segregants of the proper genotype made the procedure valuable for genetically intractable strains. Trial grape juice fermentations indicated that introduction of ho had no deleterious effect on fermentation behavior

Caffeine induces macroautophagy and confers a cytocidal effect on food spoilage yeast in combination with benzoic acid

Weak organic acids are an important class of food preservatives that are particularly efficacious towards yeast and fungal spoilage. While acids with small aliphatic chains appear to function by acidification of the cytosol and are required at high concentrations to inhibit growth, more hydrophobic organic acids such as sorbic and benzoic acid have been suggested to function by perturbing membrane dynamics and are growth-inhibitory at much lower concentrations. We previously demonstrated that benzoic acid has selective effects on membrane trafficking in 'Saccharomyces cerevisiae'. Benzoic acid selectively blocks macroautophagy in 'S. cerevisiae' while acetic acid does not, and sorbic acid does so to a lesser extent. Indeed, while both benzoic acid and nitrogen starvation are cytostatic when assayed separately, the combination of these treatments is cytocidal, because macroautophagy is essential for survival during nitrogen starvation. In this report, we demonstrate that 'Zygosaccharomyces bailii', a food spoilage yeast with relatively high resistance to weak acid stress, also exhibits a cytocidal response to the combination of benzoic acid and nitrogen starvation. In addition, we show that nitrogen starvation can be replaced by caffeine supplementation. Caffeine induces a starvation response that includes the induction of macroautophagy, and the combination of caffeine and benzoic acid is cytocidal, as predicted from the nitrogen starvation data

Improved Anaerobic Use of Arginine by Saccharomyces cerevisiae

Anaerobic arginine catabolism in Saccharomyces cerevisiae was genetically modified to allow assimilation of all four rather than just three of the nitrogen atoms in arginine. This was accomplished by bypassing normal formation of proline, an unusable nitrogen source in the absence of oxygen, and causing formation of glutamate instead. A pro3 ure2 strain expressing a PGK1 promoter-driven PUT2 allele encoding Δ(1)-pyrroline-5-carboxylate dehydrogenase lacking a mitochondrial targeting sequence produced significant cytoplasmic activity, accumulated twice as much intracellular glutamate, and produced twice as much cell mass as the parent when grown anaerobically on limiting arginine as sole nitrogen source

Does Aqueous Fullerene Inhibit the Growth of Saccharomyces cerevisiae or Escherichia coli? ▿

Studies reporting on potentially toxic interactions between aqueous fullerene nanoparticles (nC60) and microorganisms have been contradictory. When known confounding factors were avoided, growth yields of Saccharomyces cerevisiae and Escherichia coli cultured in the presence and absence of independently prepared lots of underivatized nC60 were found not to be significantly different