Extremotolerant fungi: Phylogenomics and physiology of Parengyodontium spp

Certain fungal species, such as Parengyodontium spp ., inhabit particular ecological niches. Their presence on

monuments, and in places with biomineral precipitation suggest they may play a larger role in biodeterioration

than previously thought. Studying the conditions that promote their growth and understanding the mechanisms

by which they degrade materials is crucial for the effective conservation of built heritage.

This work aims to elucidate the phylogenomic relationships between 50 Parengyodontium strains isolated

from various environments over the world and assess their extremotolerance. Whole-genome sequencing and

bioinformatic analyses were used to clarify species boundaries. Growth experiments were conducted under

extreme physiological conditions to assess tolerance to salt, pH, and temperature. Strains were cultured in

liquid media containing selected mineral salts (magnesium sulfate heptahydrate, calcium chloride hexahydrate,

sodium chloride, and magnesium chloride hexahydrate) at varying molar concentrations and pH values. Growth

response was measured using a microplate reader (Synergy H1, Biotek). Additionally, temperature tolerance was

assessed at 5, 15, 25, 30, and 37 °C, and morphological features were examined via slide culture microscopy.

The results revealed a clear phylogenomic distinction between Parengyodontium album , P. americanum , and

P. torokii , including the possible reclassifi cation of certain strains previously misidentifi ed as P. album.

Physiological tests demonstrated that low-temperature tolerance and the ability to grow in high-salt environments

are key distinguishing traits between these species with P. torokii showing greater adaptation to cold and higher

salt tolerance.

These fi ndings highlight the extremotolerant nature of Parengyodontium strains and their adaptability to the

harsh environmental conditions often present in deteriorated materials.

Their resilience and ability to metabolise diverse substrates likely contribute to their persistence and damaging

effects on materials surfaces.