Flocculence of Saccharomyces cerevisiae cells is induced by nutrient limitation, with cell surface hydrophobicity as a major determinant

Article Abstract:

An investigation was conducted to determine the physical, physiological and molecular factors involved in flocculation of Saccharomyces cerevisiae during fermentation. The results showed that flocculation requires agitation and calcium. The process is also sensitive to mannose and mannose derivatives as well as to pH. These findings imply that a calcium-dependent lectin-sugar interaction is involved in flocculation. In addition, nutrient limitation initiated an increase in cell surface hydrophobicity, resulting in flocculation ability. A cell surface protein termed flocculin could induce the flocculation process.

Analysis, Identification and classification, Membrane proteins, Cell membranes, Plasma membranes, Flocculation, Flocculation tests

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Measurement of the effects of acetic acid and extracellular pH on intracellular pH of nonfermenting, individual Saccharomyces cerevisiae cells by fluorescence microscopy

Article Abstract:

An experimental setup comprising a fluorescence microscope and a perfusion system was used to investigate the effect of acetic acid on the intracellular pH (pHi) of individual Saccharomyces cerevisiae cells at various extracellular pH (pHex) values. Results demonstrated that at pHex 3.5, 4.5 and 5.6, the pHi values of the cells decreased as the concentration of undissociated acetic acid increased from 0 to 0.10 g/L. The pHi remained constant at concentrations of undissociated acetic acid higher than 0.10 g/L.

Acetic acid, Hydrogen-ion concentration

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Green fluorescent protein as a marker for Pseudomonas spp

Article Abstract:

Plasmids expressing the green fluorescent protein (GFP) were constructed, inserted in Pseudomonas spp., and evaluated. The plasmids are maintained in pseudomonas with acceptable stability. Visualization of individual cells in mixed bacterial populations and in plant roots was made possible using this technique. The bright GFP gene was taken from the jellyfish Aequorea victoria. Plasmids containing this gene have negligible metabolic burden on host cells.

Genetic aspects, Pseudomonas, Genetic markers

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