When starving, diploid Saccharomyces cerevisiae yeasts can enter into at least two stable non-dividing states – sporulation or quiescence – and thus survive unfavorable conditions for long periods of time. However, which latent state will be preferred depends on numerous conditions. Here, we showed that budding yeasts can trigger transition into one or the other dormant state depending on the carbon source utilized. When fermentable carbon source (glucose) is present in the growth medium, the diploid S. cerevisiae entered quiescence. On the other hand, when cells were grown in the presence of the energy-rich respiratory carbon source ethanol, yeasts preferably formed ascospores. In both latent states a steady redox balance is maintained. Altogether, these findings strongly suggest that survival strategies in yeasts S. cerevisiae and transition into distinct differentiation programs depend on the cellular metabolic status.

Many biologically active compounds have been identified in the mucus of the garden snail Cornu aspersum, which are effective in the treatment of several diseases such as cancer, ulcers, wounds, etc. The incorporation of these compounds into the green synthesis of copper nanoparticles (CuONPs-Muc) was demonstrated in our previous study. Based on the synergistic effect of two reducing agents—C. aspersum snail mucus and ascorbic acid (AsA)—on CuSO₄.5H₂O, which also act as stabilizers of the resulting compound, a new method for the “green” synthesis of CuONPs-Muc is presented. Using two reducing agents has several advantages, such as forming spherical nanoparticles with a diameter of about 150 nm and reducing the formation time of CuONPs-Muc to 3 h. Analyses by ultraviolet–visible spectroscopy (UV-Vis) and Fourier transform infrared spectroscopy (FT-IR) show the formation of CuONPs-Muc, composed of a mixture of copper and copper oxide. This was confirmed by scanning electron microscopy combined with energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). Another important advantage of CuONPs obtained by the new method with two reducing agents is the stronger inhibitory effect on the bacterial growth of some Gram-positive and Gram-negative bacterial strains, compared to CuONPs-Muc prepared with only one reducing agent, i.e., a fraction of mucus with an MW > 20 kDa.

The green synthesis of metal nanoparticles, mediated by extracts from various biological sources, leads to the formation of nanoparticles with unique characteristics and potential biomedical applications. In this study, a fraction of the mucus from the snail Cornu aspersum with MW > 20 kDa was used as a bioreducing and biostabilizing agent to obtain silver nanoparticles (AgNPs) in different pH media (pH 1.5, 3.5, and 7.0). The AgNPs were characterized using UV-visible spectroscopy, SEM, TEM, XRD, and FTIR. The synthesis at pH 1.5 and pH 3.5 in the presence of two reducing agents (i.e., the C. aspersum mucus fraction with MW > 20 kDa and ascorbic acid [AsA]) resulted in the formation of well-formed spherical nanoparticles (NPs) with larger sizes (20–80 nm) than the NPs obtained at pH 7.0 (20–60 nm) in the presence of only one reducing agent. Furthermore, the biosynthesized AgNPs significantly inhibited the growth of medically significant pathogens such as Gram-positive (Bacillus subtilis NBIMCC2353, Bacillus spizizenii ATCC 6633, Staphylococcus aureus ATCC 6538, and Listeria innocua NBIMCC8755) and Gram-negative (Escherichia coli ATCC8739, Salmonella enteitidis NBIMCC8691, Salmonella typhimurium ATCC 14028, Stenotrophomonas maltophilia ATCC 17666) bacteria compared to output mucus.

Yeasts Saccharomyces cerevisiae, like other microbes in nature, respond to the unavailability of nutrients with entrance in quiescent/G₀ state. These cells exist in non-dividing, latent form by maintaining the cellular metabolism at a low level but still able to sense and adapt to environmental stresses. Their quiescent status characteristics are likely close to those of tissues and organs in mammals and humans. This fact makes them an appropriate model system for investigation of the basic mechanisms underlying the toxicity of different chemical compounds. In this study, the toxic effect of H₂O₂ and menadione on quiescent S. cerevisiae cells was evaluated through the analysis of RNA polymerases transcription profile and ribosomal RNA content. Distinct RNA polymerases subunits were expressed in G₀ yeast cells after short exposure to 0.1 mmol/L menadione and 5 mmol/L hydrogen peroxide. Significant transcription repression of RNA polymerases genes was observed as a response to menadione. Both stress agents induced changes in the 25S and 18S rRNA profile in quiescent and proliferating yeast cells. These results strongly suggest that the toxicological response of eukaryotic cells involves rapid alterations in RNA polymerases gene expression and changes in RNA transcriptome profiles, and depends on the specific mechanism of toxic action.

Several biologically active compounds involved in the green synthesis of silver and gold nanoparticles have been isolated from snail mucus and characterized. This paper presents a successful method for the application of snail mucus from Cornu aspersum as a bioreducing agent of copper sulfate and as a biostabilizer of the copper oxide nanoparticles (CuONPs-Muc) obtained. The synthesis at room temperature and neutral pH yielded nanoparticles with a spherical shape and an average diameter of 150 nm. The structure and properties of CuONPs-Muc were characterized using various methods and techniques, such as ultraviolet–visible spectroscopy (UV–vis), high-performance liquid chromatography (HPLC), one-dimensional polyacrylamide gel electrophoresis (1D-PAGE), up-conversion infrared spectroscopy Fourier transform (FTIR), scanning electron microscopy combined with energy dispersive spectroscopy (SEM/EDS), Raman spectroscopy and imaging, thermogravimetric analysis (TG-DSC), etc. Mucus proteins with molecular weights of 30.691 kDa and 26.549 kDa were identified, which are involved in the biogenic production of CuONPs-Muc. The macromolecular shell of proteins formed around the copper ions contributes to a higher efficiency of the synthesized CuONPs-Muc in inhibiting the bacterial growth of several Gram-positive (Bacillus subtilis NBIMCC2353, Bacillus spizizenii ATCC 6633, Staphylococcus aureus ATCC 6538, Listeria innocua NBIMCC8755) and Gram-negative (Escherichia coli ATCC8739, Salmonella enteitidis NBIMCC8691, Salmonella typhimurium ATCC 14028, Stenotrophomonas maltophilia ATCC 17666) bacteria compared to baseline mucus. The bioorganic synthesis of snail mucus presented here provides CuONPs-Muc with a highly pronounced antimicrobial effect. These results will expand knowledge in the field of natural nanomaterials and their role in emerging dosage forms.

The budding yeast Saccharomyces cerevisiae is a widely used model organism to investigate the changes occurring in the eukaryotic cell and to predict its possible ‘reaction’ to different environmental factors. Recently it was also shown that these microorganisms possess another advantageous ability: to ‘enter’ into quiescent state (G₀). Yeast G₀ cells have similar physiological characteristics to those of higher eukaryotes making them a better model for toxicology studies. As cadmium could affect severely human health, the main aim of the present study was to use Saccharomyces cerevisiae quiescent cells to investigate the resistance potential and corresponding adaptive response of eukaryotic cells to elevated cadmium concentrations. Both diploid and haploid yeast strains in logarithmic, quiescent and non-quiescent state were exposed to different concentrations of Cd(NO₃)₂. The half-maximal inhibitory concentration (IC₅₀) for all tested cell types was 100 µmol/L Cd(NO₃)₂. The deleterious effects of cadmium on intracellular macromolecule structures were analyzed through evaluating the levels of accumulated reactive oxygen species (ROS) and carbonylated proteins. The highest ROS concentration was measured in logarithmic cells: up to 50% versus about 8% in G₀ cells. Significant damage in protein molecules was observed in haploid cells where the protein carbonylation reached levels of 25 µmol/mg. Studying the adaptive response to elevated Cd²⁺ concentrations revealed that quiescent and non-quiescent cells respond with increased expression of key elements from the antioxidant defense system: reduced glutathione, superoxide dismutase (SOD) and catalase. Furthermore, an additional SOD izoenzyme was detected when diploid and haploid cell populations were exposed to Cd²⁺.