Growth behaviors of deep subseafloor Schizophyllum commune in response to various environmental conditions

Abstract:

[Objective] To understand the growth characteristics of deep subseafloor fungi adapted to the in-situ environment. [Methods] The growth rates of four strains of Schizophyllum commune isolated from coal-bearing sediments about 2 km below the seafloor and two strains isolated from marine and terrestrial habitats were studied by comparative culture under different environmental factors, mimicking the in-situ conditions (except for pressure) such as temperature, pH, salinity, Fe²⁺, lignin, and NH₄⁺. [Results] All the strains of subseafloor fungus grew significantly better than terrestrial (CFCC7252) and marine (MCCC 3A00233) isolated strains under the given culture conditions, including temperature (20, 30, 40, 45 ℃), oxygen (aerobic and anaerobic), pH (6, 8, 10), salinity (freshwater, in-situ water, artificial seawater), Fe²⁺ (0.27, 8.93, 89.28 μmol/L), lignin (1, 5, 10 g/L), and NH₄⁺ (0.5, 1.0, 5.0 g/L). However, there were also differences among different strains in the sedimentary environment below seafloor. The growth rate of strains 6R-2-F01 and 24R-3-F01 under anaerobic conditions was significantly higher than that of aerobic conditions. [Conclusion] Fungi from the subseafloor, such as S. commune, may have distinct biological traits that help them adapt to the extreme marine subsurface environments.