Isolation and characterization of piezotolerant fungi from Mariana Trench sediment

Hadal trenches extend below 6000 m water depth. The high hydrostatic pressures occurring in the trenches (>60 MPa) create unfriendly for life conditions. Here, we isolated 55 fungal strains from hadal (>6000 m) and non-hadal (-3500 m and 5500 m) sediments from the Mariana Trench using different pressure incubation experi-ments. The fungal strains that were successfully isolated, were assigned to Ascomycota (14 genera/25 species) and Basidiomycota taxa (5 genera/5 species). Among them, 41 fungal strains (38 isolates from Ascomycota and 3 isolates from Basidiomycota) were able to grow at hydrostatic pressures of 20 MPa, while 3 of these strains maintained successful growth at 60 MPa, which resembles the hydrostatic pressure at 6000 m water depth. Whole-genome sequencing and physiological activity data from two fungal isolates (Penicillium bialowiezense A30 and Cladosporium colombiae 601) growing at 20 MPa highlight the metabolic potential of fungal piezotolerants from the Mariana Trench in carbon (e.g., carbohydrate metabolism), nitrogen (e.g., assimilatory nitrate reduc-tion) and sulfur (e.g., assimilatory sulfate reduction) cycling. Overall, our study demonstrates the existence of piezotolerant fungi from the Mariana Trench that can grow successfully under hydrostatic pressures of 20-60 MPa and highlights their potential ecological and metabolic functions in deep sea and hadal trench ecosystems.

Automated summary

This study isolated 55 fungal strains from deep-sea sediments in the Mariana Trench, and found that 41 strains were able to grow under hydrostatic pressures of 20 MPa. The study also highlighted the metabolic potential of these fungi in carbon, nitrogen, and sulfur cycling.