Author/Editor		Kogej, Tina; Ramos, Jose; Plemenitaš, Ana; Gunde-Cimerman, Nina
Title		The halophilic fungus Hortaea werneckii and the halotolerant fungus Aureobasidium pullulans maintain low intracellular cation concentrations in hypersaline environments
Type		članek
Source		Appl Environ Microbiol
Vol. and No.		Letnik 71, št. 11
Publication year		2005
Volume		str. 6600-5
Language		eng
Abstract		Hortaea werneckii and Aureobasidium pullulans, black yeast-like fungi isolated from hypersaline waters of salterns as their natural ecological niche, have been previously defined as halophilic and halotolerant microorganisms, respectively. In the present study we assessed their growth and determined the intracellular cation concentrations of salt-adapted and non-salt-adapted cells of both species at a wide range of salinities (0 to 25% NaCI and 0 to 20% NaCI, respectively). Although 5% NaCI improved the growth of H. werneckii, even the minimal addition of NaCI to the growth medium slowed down the growth rate of A. pullulans, confirming their halophilic and halotolerant nature. Salt-adapted cells of H. werneckii and A. pullulans kept very low amounts of internal Na+ even when grown at high NaCI concentrations and can be thus considered Na+ excluders, suggesting the existence of efficient mechanisms for the regulation of ion fluxes. Based on our results, we can conclude that these organisms do not use K+ or Na+ for osmoregulation. Comparison of cation fluctuations after a hyperosmotic shock, to which nonadapted cells of both species were exposed, demonstrated better ionic homeostasis regulation of H. werneckii compared to A. pullulans. We observed small fluctuations of cation concentrations after a hyperosmotic shock in nonadapted A. pullulans similar tu those in salt-adapted H. werneckii, which additionsilly confirmed better regulation of ionic homeostasis in the latter. These features can be expected from organisms adapted to survival within a wide range of salinities and to occasional exposure to extremely high NaCI concentrations, both characteristic for their natural environment.
Descriptors		YEASTS SODIUM CHLORIDE SODIUM POTASSIUM