Adaptive Role of Cell Death in Yeast Communities Stressed with Macrolide Antifungals.

Microorganisms cooperate with each other to protect themselves from environmental stressors. An extreme case of such cooperation is regulated cell death for the benefit of other cells. Dying cells can provide surviving cells with nutrients or induce their stress response by transmitting an alarm signal; however, the role of dead cells in microbial communities is unclear. Here, we searched for types of stressors the protection from which can be achieved by death of a subpopulation of cells. Thus, we compared the survival of Saccharomyces cerevisiae cells upon exposure to various stressors in the presence of additionally supplemented living versus dead cells. We found that dead cells contribute to yeast community resistance against macrolide antifungals (e.g., amphotericin B [AmB] and filipin) to a greater extent than living cells. Dead yeast cells absorbed more macrolide filipin than control cells because they exposed intracellular sterol-rich membranes. We also showed that, upon the addition of lethal concentrations of AmB, supplementation with AmB-sensitive cells but not with AmB-resistant cells enabled the survival of wild-type cells. Together, our data suggest that cell-to-cell heterogeneity in sensitivity to AmB can be an adaptive mechanism helping yeast communities to resist macrolides, which are naturally occurring antifungal agents. IMPORTANCE Eukaryotic microorganisms harbor elements of programmed cell death (PCD) mechanisms that are homologous to the PCD of multicellular metazoa. However, it is still debated whether microbial PCD has an adaptive role or whether the processes of cell death are an aimless operation in self-regulating molecular mechanisms. Here, we demonstrated that dying yeast cells provide an instant benefit for their community by absorbing macrolides, which are bacterium-derived antifungals. Our results illustrate the principle that the death of a microorganism can contribute to the survival of its kin and suggest that early plasma membrane permeabilization improves community-level protection. The latter makes a striking contrast to the manifestations of apoptosis in higher eukaryotes, the process by which plasma membranes maintain integrity.

[Evaluation of the effect of various methods of oil-polluted soil bioremediation on micromycete complexes].

The influence of remediation of oil-contaminated gray forest, dark gray forest, and black soils by biological preparations Bacispecin, Devoroil, and Belvitamil on the population of opportunistic and phytotoxic fungi was studied. It was found that this population increased after oil pollution and decreased after three months of remediation. The latter is a sign of gradual recovery of soil microbiota.

[Mathematical simulation of accumulation of opportunistic micromycetes in petroleum-polluted soils].

The impact of pollution of different types of soils (leached chernozem, grey wood and dark-grey wood soils) with petroleum and its products on the size, species-specific composition, and accumulation of opportunistic micromycetes was studied in long-term field microallotment and laboratory conditions. Petroleum and its refining products were shown to increase the size of micromycetes and to change their structure and species diversity. A mathematical model has been developed, which describes the time course of changes in the size of mushroom propagules under different environmental conditions.

[Prodigiosin as a possible inhibitor of Serratia marcescens nuclease]. / Izuchenie prodigiozina kak vozmozhnogo ingibitora nukleazy Serratia marcescens.

Preparations of prodigiosin inhibited the activity of nuclese of Serratia marcescens. The preparations were fractionated on an alumina column. The activity of nuclease was inhibited by both fractions containing pyrryldipyrrylmethene compounds and fractions in which these compounds were not found by spectrophotometry. The inhibitor was isolated also from the cells of a pigmentless strain. Therefore, the inhibition is exhibited by compounds that are extracted from the cells with acetone and petroleum ether, rather than by prodigiosin.

[Effect of the cholesterol breakdown rate in the body on the dynamics of the development of alimentary hypercholesterinemia in rabbits]. / Vliianie skorosti raspada kholesterina v organizme na dinamiku razvitiia alimentarnoi giperkholesterinemii u krolikov

A mathematical equation of the shift of the dynamic balance of cholesterolemia to a new level is substantiated. A mathematical analysis of the results of experimental studies is presented. A correlation was established between the mechanism of the development of alimentary hypercholesterolemia in rabbits and the half-life period of cholesterol in the body (T1/2 per day). It is demonstrated that an equilibrium level of hypercholesterolemia (Xeqn,ch, mg%) is directly proportional to the speed of cholesterol accumulation in blood (Vch, mg%/day) and reciprocal to the constant rate of cholesterol decomposition in the body.