The influence of acetic and propionic acids on baker's yeast was investigated in order to expand our understanding of the effect of weak organic acid food preservatives on eukaryotic cells. Both acids decreased yeast survival in a concentration-dependent manner, but with different efficiencies. The acids inhibited the fluorescein efflux from yeast cells. The inhibition constant of fluorescein extrusion from cells treated with acetate was significantly lower in parental strain than in either PDR12 (ABC-transporter Pdr12p) or WAR1 (transcriptional factor of Pdr12p) defective mutants. The constants of inhibition by propionate were virtually the same in all strains used. Yeast exposure to acetate increased the level of oxidized proteins and the activity of antioxidant enzymes, while propionate did not change these parameters. This suggests that various mechanisms underlie the yeast toxicity by acetic and propionic acids. Our studies with mutant cells clearly indicated the involvement of Yap1p transcriptional regulator and de novo protein synthesis in superoxide dismutase up-regulation by acetate. The up-regulation of catalase was Yap1p independent. Yeast pre-incubation with low concentrations of H 2 O 2 caused cellular cross-protection against high concentrations of acetate. The results are discussed from the point of view that acetate induces a prooxidant effect in vivo, whereas propionate does not.

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Fluorescein efflux from S. cerevisiae cells was measured to study the peculiarities of fluorescein transport system, which is important for yeast resistance to certain drugs and weak organic acid preservatives. Glucose-independent and glucose-stimulated fluorescein effluxes were characterized using iodoacetate, cyanide and orthovanadate, inhibitors of glycolysis, electron transport chain, and ATPases, respectively. It is supposed that in glucose-free medium fluorescein extrusion is ATP-dependent and the energy for this efflux is mainly provided by respiration. In glucose-containing medium, glycolysis plays a critical role for extrusion of fluorescein. The results indicate that acetic acid inhibits the fluorescein efflux from yeast cells. The inhibition constant of glucose-stimulated fluorescein efflux is significantly lower in parental strain than in two mutants defective in PDR12 (ABC-transporter Pdr12p) or WAR1 (transcription factor of Pdr12p). It can be suggested that the membrane protein Pdr12 is involved in fluorescein extrusion from the yeast cells, but component(s) other than Pdr12p is (are) also important.

Last years, the concept of resistant starch (RS) has evoked a new interest in researchersin the context of bioavailability of starch and its use as a source of dietary fiber. Based on clinicaland animal research, RS has been proposed to be the most potentially beneficial starch fraction forhuman health. In this study, the effects of amylose starch as a fraction of RS on development andlifespan of fruit fly Drosophila melanogaster were investigated. In both Canton S and w1118 strains, thediet with 20% amylose RS delayed fly development, increased triacylglyceride level in the body ofadult insects and reduced their lifespan compared to the diet with 4% amylose starch. Thus, ourdata clearly demonstrate that amylose starch at high concentrations may negatively affect fruit fly

The war launched by Russia has created new challenges for universities, including massive student migration abroad and massive displacement of students within Ukraine from the frontline areas. Many students lost access to quality education or had their studies interrupted by the war. Recognizing these problems, universities are trying to find different solutions. One such approach may be to introduce inter-university online courses that will be recognized by partner universities. In this case study, we analyze the effectiveness of inter-university online courses as an approach to restoring education for students severely affected by the war and as a way to maintain the quality of education in small groups at universities. The online course "Integrated Life Science Course" was taken for analysis, which was taught both to biology students from different universities in Ukraine within the framework of the educational project supported by German Academic Exchange Service (DAAD). Using statistics on course registration and attendance, as well as interview methodology, we assessed students' motivation to participate in this online course, course satisfaction, and learning outcomes, and identified shortcomings and pitfalls to avoid in similar courses. The survey and the results of the final test show that the main motivator for students to register and study at the course was the desire to gain new knowledge for further professional growth. A scholarship was also an important argument to enroll in the course; however, it did not impact the motivation of students to study. The fraction of students that successfully passed the final exam (~70%) was equal in the cohorts that had and had not been awarded scholarships. Thus, the scholarship was not a motivator to complete the course and successfully pass the exam to receive the certificate. Therefore, in order for such courses to be productive and effective, it is necessary to emphasize student motivation during selecting procedure.