Salt tolerance adaptations in Aspergillus sydowii EXF-12860: first study that demonstrates the physiological fitness of a filamentous ascomycete in a saturated NaCl solution

Water activity (aw) is a thermodynamic descriptor that indicates how much water is free in an aqueous solution. This parameter is thus critical for microbes, and the microbial growth is severely restricted below of a certain aw level (aw<0.90). So, high NaCl concentrations are undoubtedly hostile for life and impose an extensive transcriptional reprograming to support the physiological acclimation mechanisms to sustain the microbial growth at hypersaline conditions. The cellular effects of water deprivation have been poorly studied in aspergilli. Here we assessed salt tolerance adaptations in Aspergillus sydowii through microscopy studies, synthesis of compatible solutes, and the oxidative balance. Also we implemented transcriptomics and metabolomics approaches. These results make it possible to establish a relationship between the morphological changes produced at different NaCl concentrations and the genes related to these changes by means of comparative transcriptomic analysis. This study demonstrates that A. sydowii is transcriptional and metabolically active under water deprivation by saturated NaCl concentrations.