Effect of hyperbaric stress on yeast morphology: study by automated image analysis

Abstract

The effects of hyperbaric stress on the morphology of Saccharomyces cerevisiae were studied in batch cultures under pressures between 0.1 MPa and 0.6 MPa and different gas compositions (air, oxygen, nitrogen or carbon dioxide), covering aerobic and anaerobic conditions. A method using automatic image analysis for classification of S. cerevisiae cells based on their morphology was developed and applied to experimental data. Information on cell size distribution and bud formation throughout the cell cycle is reported. The results show that the effect of pressure on cell activity strongly depends on the nature of the gas used for pressurization. While nitrogen and air to a maximum of 0.6 MPa of pressure were innocuous to yeast, oxygen and carbon dioxide pressure caused cell inactivation, which was confirmed by the reduction of bud cells with time. Moreover, a decrease in the average cell size was found for cells exposed for 7.5 h to 0.6 MPa CO2.

Influence of environmental and nutritional conditions on yeast–mycelial dimorphic transition in Trichosporon cutaneum

“…Dimorphism is a peculiar characteristic of several yeast species and filamentous fungi, such as Candida albicans, Saccharomyces cerevisiae, Yarrowia lypolitica, Pichia fermentans, Schizosaccharomyces japonicus, Ustilago maydis, Ophiostoma floccosum, Ceratocystis ulmi, Mycosphaerella graminicola, which can switch between unicellular yeast and multicellular filamentous growth forms in response to changing environmental cues [1][2][3][4][5][6][7][8]. Usually, in the yeast stage, mitotic divisions either by budding or fission to produce two independent cells, while in the filamentous stage, cells become elongated yet fail to abscise following cytokinesis, and remain attached to form chains of elongated pseudohyphal cells; the true hyphae are produced with long continuous tubes and septae separating each of the nuclei in these tubes [2].…”

Modelización del crecimiento de una población microbiana en medio líquido y su implicación en el estudio de la morfología celular a través del análisis digital de imágenes

“…Hay que tener en cuenta que la tasa de crecimiento, mutación y condiciones ambientales también afectan el tamaño y forma de la levadura. Y que la morfología de estas células estáíntimamente relacionada con su estado fisiológico (Coelho et al, 2004) y su estado en el ciclo celular.…”

“…La elongación es un descriptor de forma que nos da información sobre la deformación de la células y se define como la relación entre el diámetro mayor y diámetro menor. Para diferenciar entre una célula está que está gemando y otra que no, se puede tomar un valor de elongación de referencia igual 1.5 (Coelho et al, 2004). La Figuras 29 y 30 nos muestran histogramas de la variable elongación correspondientes a células creciendo en condiciones aerobias.…”

Effects of moderate pressure on premeability and viability of Saccharomyces cerevisiae cells

“…To understand the impact of high pressure on cell viability, different approaches have also been developed. The results from some investigations showed that high pressure (more than 10 MPa) brought about significant changes in a microorganism's morphology [3,4], metabolic flux [5,6], gene expression [7,8] and the permeability of the cell membrane etc. [9,10,12,13].…”