A study on microbial flora and environmental factors related to selerotium grain formation

菌核颗粒是外生菌根真菌的静息体，在森林土壤中形成黑色球形结构，由厚实的黑色素壁保护。通过对菌核颗粒形成相关的微生物区系和环境因子的研究，阐明菌核颗粒发育在土壤生态系统中的共生功能。用x射线光电子能谱法测定了菌核中主要元素C、Al、O的含量和化学结合状态。在籽粒内微生物区系的实验中，预计分离到的C. geophilum尚未成功，除了与粘液红杆菌（Rhodotorula mucilaginosa spp）相关的菌株外，大多数菌株都是未知种。细菌群落分析显示，α变形菌属（Alphaproteobacteria）占优势，主要是鞘氨单胞菌（Sphingomonas）群。我们的鞘氨单胞菌不太可能对铝毒性有显著的耐受性。研究了德国哈茨山Podsole、Braunfahlerde和Braunerde-Podsoles森林土壤以及日本中部Myoko山和秋田- komagatake山火山灰土壤中真菌菌核颗粒的分布与土壤化学性质的关系。日本安土中已证实，哈尔茨地区不同森林土壤菌核颗粒的形成受活性铝状态和有毒铝（Al3+）含量的强烈调控。阐明了不论土壤类型和土壤酸度强弱，铝的存在与硒的发育之间的关系。

Sclerotium grains, the resting bodies of ectomycorhizal fungi, are formed in forest soils as black spherical structures protected by thick and melanin-pigmented walls. Microbial flora and environmental factors related to the formation of sclerotium grains were studied to elucidate the symbiotic function of selerotium grain development in soil ecosystem. The content and chemical binding states of the major elements, C, Al, and O, in sclerotium gains were examined by X-ray photoelectron spectroscopy analysis. As for the experiments on the microbial flora inside the grains, the expected isolation of C. geophilum was not yet successful and most of the isolates were unknown species except strains relative to Rhodotorula mucilaginosa spp. Bacterial community analysis revealed the predominance of Alphaproteobacteria, chiefly the Sphingomonas group. It was unlikely that our Sphingomonas isolates had remarkable tolerance to aluminum toxicity. The relationships between the distribution of fungal sclerotium grains and soil chemical properties were studied in forest soils of Podsole, Braunfahlerde and Braunerde-Podsoles in Harz Mts., Germany and in volcanic ash soils of Mt. Myoko, and Mt. Akita-Komagatake, Central Japan. The formation of sclerotium grains in various forest soils of the Harz Mts. was strongly regulated by the state of active aluminum and the content of toxic Al (Al3+) as confirmed in Japanese Andosols. The relationship between the existence of aluminum and selerotium development was elucidated regardless of the soil type and the strength of soil acidity.