Characteristics of Cenococcum geophilum sclerotia found in steppe forest soil in Mongolia

Sclerotia are the resting bodies of fungi. The exact biochemical properties of melanized sclerotia that allow them to remain in the soil and retain their structure are unclear. Sclerotium grains were collected from Mongolian steppe forest soils to elucidate the characteristics of melanized sclerotia in semi-arid areas. The collected sclerotia were characterized as derived from Cenococcum geophilum based on similarities in the ITS1-5.8S-ITS2 region. Using accelerator mass spectrometry 14C/12C measurement, the mean residual time of the sclerotium in the soil was estimated to be 40 years. The H2O content of the grains was 10%, and the major element compositions were 43% C, 39% O (with H), and 1.8% N. Scanning electron microscope-energy dispersive X-ray spectrometry analysis showed that C, O, and Ca were the dominant elements and Al, K, and Mg were distributed homogeneously in the grain, while Ca and P specifically coexisted in cell compartments in the form of Ca-phosphate (hydroxyapatite) with a concentric location inside the grains. Hydroxyapatite precipitation in sclerotia may suggest a form of P sequestration in slightly alkaline soils.