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

摘要

Results of Positron Annihilation Lifetime Spectroscopy (PALS) and microscopicstudies on simple microorganisms: brewing yeasts are presented. Lifetime ofortho - positronium (o-Ps) were found to change from 2.4 to 2.9 ns (longerlived component) for lyophilised and aqueous yeasts, respectively. Alsohygroscopicity of yeasts in time was examined, allowing to check how water -the main component of the cell - affects PALS parameters, thus lifetime of o-Pswere found to change from 1.2 to 1.4 ns (shorter lived component) for the driedyeasts. The time sufficient to hydrate the cells was found below 10 hours. Inthe presence of liquid water an indication of reorganization of yeast in themolecular scale was observed. Microscopic images of the lyophilised, dried and wet yeasts with bestpossible resolution were obtained using Inverted Microscopy (IM) andEnvironmental Scanning Electron Microscopy (ESEM) methods. As a result visiblechanges to the surface of the cell membrane were observed in ESEM images.