title: Monitoring the intracellular pH of Zygosaccharomyces bailii by green fluorescent protein.
abstract: It is generally known that intracellular pH (pH(i)) plays a vital role in cell physiology and that pH(i) homeostasis is essential for normal cellular functions. Therefore, it is desirable to know the pH(i) during cell life cycle or under various growth conditions. Different methods to measure pH(i) have been developed and among these methods, the use of pH-sensitive green fluorescent protein (GFP) as a pH(i) indicator is a promising technique. By using this approach, not only can more accurate pH(i) results be obtained but also long-term experiments on pH(i) can be performed. In this study, the wild type Zygosaccharomyces bailii, a notorious food spoilage yeast, was transformed with a plasmid encoding a pH-sensitive GFP (i.e. pHluorin), enabling the pH(i) of the yeast to be determined based on cellular fluorescent signals. After the transformation, growth and pH(i) of the yeast were investigated in four different acidic conditions at 22°C during 26days. From the experimental results, the transformation effectiveness was verified and a good correlation between yeast growth and pH(i) was noticed. Particularly, it was observed that the yeast has an ability to tolerate a significant pH(i) drop during exponential phase and a subsequent pH(i) recovery in stationary phase, which may underlie the exceptional acid resistance of the yeast. This was the first time that a GFP-based approach for pH(i) measurement was applied in Z. bailii and that the pH(i) of the yeast was monitored during such a long period (26days). It can be expected that greater understanding of the physiological properties and mechanisms behind the special acid resistance of the yeast will be obtained from further studies on this new yeast strain.
authors.affiliation: Department of Food Safety and Food Quality, Member of Food2Know, Ghent University, Ghent, Belgium.
authors.forename: T D T
authors.initials: TD
authors.lastname: Dang
authors.forename: S L
authors.initials: SL
authors.lastname: De Maeseneire
authors.forename: B Y
authors.initials: BY
authors.lastname: Zhang
authors.forename: W H
authors.initials: WH
authors.lastname: De Vos
authors.forename: A
authors.initials: A
authors.lastname: Rajkovic
authors.forename: A
authors.initials: A
authors.lastname: Vermeulen
authors.forename: J F
authors.initials: JF
authors.lastname: Van Impe
authors.forename: F
authors.initials: F
authors.lastname: Devlieghere
mesh_terms: D000143:Acids / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D010957:Plasmids / Q000235:genetics; D020068:Zygosaccharomyces / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*
chemical_list: D000143:Acids; D049452:Green Fluorescent Proteins