Topografia tridimensional de células-mães e filhas de Saccharomyces cerevisiae antes e após o estresse por alta pressão hidrostática

Abstract

Saccharomyces cerevisiae, a yeast with several economic and biotechnological application, is a model organism in studies of stress and longevity. According to studies, organisms that respond better to stress reach longer life. The high pressure hydrostatic (HHP) stress generates cellular response similar to the other stresses suffered by yeasts in fermentation tanks. The atomic force microscope (AFM) is a tool that generates three-dimensional images, providing accurate data on the morphological and chemical characteristics of yeasts. The objective of this study was to analyzer the morphological characteristics of mother and daughter cells of the S. cerevisiae and after treatment by HHP to 100 MPa for 30 minutes. After the treatment, images was made in AFM in intermittent contact reading mode and phase mode. Relative roughness variation between the highest and lowest value found obtained from 11 cells in each experimental group, being made boxplots. An AFM calibration test was performed on glass coverslip and also was developed a program to create graphic representations of mother and daughter yeasts at ambient pressure and after aplication to 100 MPa from the averages of roughness obtained in the readings. The calibration test increased the reliability of the obtained data. Mothers and daughters cells at 0,1 MPa presented a dispersed roughness distribution, but the daughter cells presented lower uniformity (29-51%) of the surface than the mothers (18-41%). Mother cells after treatment by HHP to 100 MPa was showed to have greater roughness uniformity than at 0.1 MPa. Daughter cells after treatment by HHP also showed greater uniformity in their roughness profile than it at ambient pressure. After application of 100 MPa to HHP, daughter cells was showed to suffer more from the effects of stress, being more uniform than the cells submitted to the same conditions. The increased uniformity of the surface of the mother cells and daughters after treatment by HHP may be due to their compression during the pressurizing process. From the roughness averages, three-dimensional graphical representations of the yeasts (static and animated) was assembled. The program was effective, presenting in a simple and visual form the numerical data of the work. Thus, with the data obtained, it was possible to observe that the piezo stress differently affects the mother cells and daughters of Saccharomyces cerevisiae and this may be due to both the cell wall composition of these yeasts and to the molecular factors involved in the stress response. These and other results may aid in the elucidation of the mechanisms utilized by S. cerevisiae in stress response.