Characteristics of <i>Cenococcum geophilum</i> 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 <i>Cenococcum geophilum</i> 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.

菌核（sclerotia）是真菌的休眠体。目前尚不清楚黑化菌核（melanized sclerotia）能够在土壤中存活并维持自身结构的具体生化特性。研究团队从蒙古草原森林土壤中采集了菌核颗粒，旨在阐明半干旱地区黑化菌核的相关特征。经ITS1-5.8S-ITS2区域序列相似性分析，采集到的菌核被鉴定为源自土生空团菌（*Cenococcum geophilum*）。通过加速器质谱（accelerator mass spectrometry）测定¹⁴C/¹²C比值，研究人员估算出该类菌核在土壤中的平均滞留时间为40年。该菌核颗粒的含水量为10%，主要元素组成为：碳43%、氧（含氢）39%以及氮1.8%。扫描电子显微镜-能量色散X射线光谱（scanning electron microscope-energy dispersive X-ray spectrometry）分析结果显示：碳、氧与钙为该颗粒的主要元素；铝、钾和镁在颗粒内部均匀分布；而钙与磷则以磷酸钙（羟基磷灰石，hydroxyapatite）的形式特异性共存于细胞区室中，并在颗粒内部呈同心环状分布。菌核内羟基磷灰石的沉积现象，或暗示了弱碱性土壤中一种磷固存的潜在机制。