Prilagoditve gliv na izjemno visoke koncentracije soli / Fungal adaptation to extremely high salt concentrations

author: Nina Gunde-Cimerman, Biotehniška fakulteta, Univerza v Ljubljani
published: Oct. 21, 2011,   recorded: October 2011,   views: 197
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Okolja kjer se fizikalno-kemijski parametri približajo vrednostim blizu zgornjim mejam življenja, imenujemo ekstremna. V primeru izjemno slanih okolij je omejujoč dejavnik visoka koncentracija NaCl in drugih soli, ki ga pogosto spremljajo še drugi tipi stresa, kot so visoke temperature, visoko UV-sevanje, nizke koncentracije kisika in nihanje hranil. Danes vemo, da lahko mikrobno življenje obstaja v celotnem razponu slanosti, ki jih najdemo v naravnih okoljih, od sladkovodnih voda do vod, nasičenih z natrijevim kloridom. Izjemno slana okolja naseljujejo obsežne mikrobne združbe bakterij, arhej, alg, praživali in gliv. V tem prispevku se bomo osredotočili na najbolj uspešne evkariontske mikroorganizme v izjemno slanih vodah solarnih solin – glive, in sicer na prevladujočo vrsto, črno kvasovko Hortaea werneckii. Ta v slanem okolju izjemno uspešno nadomesti izgubo turgorja in prepreči toksičnost natrijevih ionov, kar ji omogoča rast celo v raztopinah, skoraj nasičenih z NaCl. Negativni vpliv hiperozmolarnega okolja prepreči s povečanim prispevkom energije, potrebne za dva energetsko potratna procesa: izločanje ionov, ki vdirajo v celico, nazaj v okolje in za sintezo kompatibilnih topljencev. Integriteto in delovanje celic pod stresom vzdržuje s spremembami v sestavi membran in celične stene. Razumevanje odgovorov na povišano slanost pri črni kvasovki H. werneckii in drugih glivah je razširilo naše znanje o odpornosti mikrobov/ gliv na stres in spodbudilo uporabo trenutno ne dovolj izkoriščenega biotehnološkega potenciala gliv, ki živijo v skrajnostnih okoljih.


Environments where physicochemical parameters have values close to the bottom or top limits known for life can be considered as extreme environments. In the case of hypersaline environments, the limiting factor is high concentration of NaCl and other salts, which are frequently accompanied by other types of stress, such as high temperature, high UV radiation, low oxygen concentration, or fluctuating nutrients. We now know that microbial life can exist over the whole range of salt concentrations that are found in natural habitats, from freshwater environments to waters saturated with sodium chloride. Hypersaline environments support substantial microbial communities of selected halotolerant and halophilic organisms, including bacteria, archaea, algae, protozoa and fungi. In this article we will focus on the most successful eukaryotic microbes – fungi in hypersaline water of solar salterns, represented by the dominant species, the black yeast Hortaea werneckii. It has an outstanding ability to overcome the turgor loss and sodium toxicity that are typical for hypersaline environments which facilitates its growth even in solutions that are almost saturated with NaCl. The negative impact of a hyperosmolar environment is counteracted by an increase in the energy supply that is needed to drive the energy demanding export of ions and synthesis of compatible solutes. Changes of membrane lipid composition and cell-wall structure maintain the integrity and functioning of the stressed cells. Understanding salt responses of H. werneckii and other fungi will extend our knowledge of microbial/fungal stress tolerance and promote the use of the currently unexploited biotechnological potential of fungi that live in hypersaline environments.

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