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Biophysical Manipulation of the Extracellular Environment by Eurotium halophilicum

Summary

Eurotium halophilicum is a remarkable fungus found on old books that can survive in extremely dry conditions by using salt crystals to pull water from the air. The fungus covers itself with hair-like structures and produces sticky polymers that help it maintain moisture. This ability to thrive in seemingly dry environments makes it a challenge for museums and libraries trying to preserve old books, and climate change may make this problem worse.

Background

Eurotium halophilicum is a psychrotolerant, halophilic ascomycete and one of the most extreme xerophiles known, capable of growing near 0°C and at water activity as low as 0.651. The mechanisms by which this fungus adapts to extreme stress conditions in dynamic water environments remain poorly understood, particularly in its common occurrence on library book surfaces.

Objective

This study investigated the biophysical interactions of E. halophilicum with its extracellular environment on book surfaces, examining fungal morphology, extracellular polymeric substances, salt crystals, and water-relations strategies that enable its extreme xerophilicity.

Results

E. halophilicum hyphae were covered with hair-like microfilaments and embedded in extracellular polymeric substances rich in sodium, sulfur, and calcium. Crystals of eugsterite and mirabilite were identified associated with fungal colonies. The fungus appears to use salt deliquescence to maintain water-activity conditions within its metabolic window, with conidia concentrated in phosphorus and potassium.

Conclusion

E. halophilicum employs a multi-faceted strategy including microfilaments, compatible solutes, extracellular polymeric substances, and salt deliquescence to maintain hydration and regulate biophysical conditions in seemingly dry environments, allowing persistence in libraries and other built environments under climate change conditions.
  • Published in:Pathogens,
  • Study Type:Experimental Research,
  • Source: PMID: 36558795, DOI: 10.3390/pathogens11121462
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