Characterisation of intracellular gas bubbles in Saccharomyces
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Date
2019-01
Authors
Dithebe, Khumisho
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
The yeast fermentation process is well established. However, until recently no
sign of intracellular gas bubbles had been reported. A paradigm shift emanated
when intracellular gas bubbles were discover using various microscopy techniques
thereby resolving the missing link between CO2 production and eventual release
from the cells. The lack of membranes around the gas bubbles served as a
distinguishing feature of the bubbles. However, there had been other non-enveloped
structure that had been reported as either lipid droplets or vacuole fragments. This
study, using organelle-specific fluorescent probes, shows that intracellular gas
bubbles, lipid droplets and vacuole fragments are separate inclusions that can coexist
in the cell. Considering that intracellular gas bubbles compress and deform
organelles, coupled to the fact that yeast cells have an internal pressure of 2.1 MPa
and that pressurised CO2 has been reported to have adverse effects on
microorganisms warranted an investigation into the effect of intracellular gas bubbles
on cell function. This study concludes that the formation of intracellular gas bubbles
did not have a negative effect on mitochondrial activity. The observation of
fermenting S. pastorianus cells (more gas bubbles) having lower lipid content than
respiring cells (few gas bubbles) indicates that the gas bubble formation plays a role
in controlling the buoyant cell density of fermenting in this strain. This suggests that
the influence of bubble formation may be limited and strain dependent.
Description
Keywords
Buoyant density, Chemostat cultures, Cell surface hydrophobicity, Fermentation, Intracellular gas bubbles, S. pastorianus, S. cerevisiae, Physiology, Thesis (Ph.D. (Microbial, Biochemical and Food Biotechnology))--University of the Free State, 2019