Studies of unicellular micro-organisms Saccharomyces cerevisiae by means of Positron Annihilation Lifetime Spectroscopy

TL;DR

This study uses Positron Annihilation Lifetime Spectroscopy and microscopy to analyze structural and water content changes in Saccharomyces cerevisiae yeasts, revealing how hydration affects cellular properties and organization.

Contribution

It introduces PALS combined with microscopy to investigate microstructural and hydration effects in yeast cells, providing new insights into cellular water interactions.

Findings

Positronium lifetime varies with yeast hydration state.

Water influences PALS parameters and cellular reorganization.

Microscopy reveals surface changes in yeast cells upon hydration.

Abstract

Results of Positron Annihilation Lifetime Spectroscopy (PALS) and microscopic studies on simple microorganisms: brewing yeasts are presented. Lifetime of ortho - positronium (o-Ps) were found to change from 2.4 to 2.9 ns (longer lived component) for lyophilised and aqueous yeasts, respectively. Also hygroscopicity of yeasts in time was examined, allowing to check how water - the main component of the cell - affects PALS parameters, thus lifetime of o-Ps were found to change from 1.2 to 1.4 ns (shorter lived component) for the dried yeasts. The time sufficient to hydrate the cells was found below 10 hours. In the presence of liquid water an indication of reorganization of yeast in the molecular scale was observed. Microscopic images of the lyophilised, dried and wet yeasts with best possible resolution were obtained using Inverted Microscopy (IM) and Environmental Scanning Electron Microscopy (ESEM) methods. As a result visible changes to the surface of the cell membrane were observed in ESEM images.