Outlines for the definition of halotolerance/halophily in yeasts: () CBS4019 as the archetype?

Abstract

Candida versatilis (halophila) CBS4019 was chosen to study the physiological reactions of long-term exposure to extremely high salt concentrations. In general, our results show a significant increase in enzyme expression during growth under stress conditions. Although glycerol and mannitol pathways are not under glucose repression, they were found to be metabolically regulated. Glycerol-3P-dehydrogenase used either of its cofactors NADPH or NADH, being in favor of NADPH during growth with high salt concentrations. This ability of interchanging cofactors, an increased fermentation rate, and the observed mannitol pathway activity are suggested to contribute to the yeasts' redox stability. Enzymes per se were not salt-tolerant in vitro. Consistently, intracellular sodium was low and intracellular potassium, a requirement for growth, was high. The concept of halophily and its applicability to yeasts is discussed.

Plasma-membrane Cnh1 Na+/H+ antiporter regulates potassium homeostasis in Candida albicans

“…In general, C. albicans is more halotolerant than the most studied yeast S. cerevisiae (Silva-Graca et al, 2003). In our experience, C. albicans cells grew in the presence of 2300 mM salts whereas S. cerevisiae wild-types usually do not tolerate more than 1800 mM NaCl or 2000 mM KCl (Kinclova et al, 2001a and our unpublished results).…”

Expression of glycerol 3‐phosphate dehydrogenase gene (CvGPD1) in salt‐tolerant yeast Candida versatilis is stimulated by high concentrations of NaCl

“…Silvia-Graca et al reported that NADP + -dependent GPDH specific activity in C. versatilis (halophila) increases with NaCl concentration in culture medium (Silva-Graca et al, 2003b). In that report, the activity in C. versatilis (halophila) cells grown in the absence of NaCl and in presence of 1 M NaCl and 2 M NaCl showed comparable values to the activity in cells in the presence of 3 M NaCl.…”

“…The main compatible solutes in C. versatilis yeast cells are polyol, glycerol and mannitol (Onishi and Suzuki, 1968). The physiology of C. versatilis (halophila) and the analyses of various enzyme activities have been reported by Silva-Graca et al (2003a, 2003b.…”

Adaptation to Life at High Salt Concentrations in Archaea, Bacteria, and Eukarya

“…However, this is not the case for eukaryotic microorganisms, much less information is available and only a few genera have been studied. In fact even the concept of a halophilic eukaryotic microbe is not completely established and, for example, the existence of real halophilic yeasts is still controversial (Silva-Graça et al, 2003), in spite of the fact that one Candida species has been named C. halophila (Kurtzman and Fell, 2000). In any case, algae such as Dunaliella Katz et al, 1989), filamentous fungi such as Penicillium or Aspergillus (Cuppers et al, 1997;Mert and Ekmekci, 1987), yeasts such as Debaryomyces or yeast-like fungal species such as Hortaea can be found in salty environments, and these are attractive organisms to study salt tolerance mechanisms and salt stress responses in eukaryotic cells.…”

“…They found that among several marine occurring yeast, D. hansenii was the one least affected by high NaCl concentrations Norkrans and Kylin, 1969). Since then D. hansenii has been defined as a halotolerant (Alba-Lois et al, 2004), halophilic (González-Hernandez et al, 2004), or even salt-loving yeast (Silva-Graça et al, 2003), a concept that I will also use in this chapter.…”