NITROGEN-FIXING BACILLUS SP ASSOCIATED WITH DOUGLAS-FIR TUBERCULATE ECTOMYCORRHIZAE
NITROGEN-FIXING BACILLUS SP ASSOCIATED WITH DOUGLAS-FIR TUBERCULATE ECTOMYCORRHIZAE
复制标题
DOI：
10.1007/bf00012804
复制
发表时间：
1992-02-01
期刊：
影响因子：
4.9
通讯作者：
MOORE, LVH
中科院分区：
文献类型：
--
作者：
LI, CY;MASSICOTE, HB;MOORE, LVH
在微需氧条件下，通过乙炔还原测定了豆杉外生菌根固氮酶活性。瘤状外生菌根由密集堆积的外生菌根组成，外生菌根被一层类似真菌的附着层包裹着。固氮酶活性主要集中在外层，添加蔗糖后，固氮酶活性显著增强。分离出的细菌是一种固氮芽孢杆菌，是一种需氧菌，但需要厌氧条件才能产生固氮酶活性。真菌在结核复合体中的呼吸作用。根和相关的菌根圈微生物可能有助于维持微好氧生态位，在那里可以进行固氮。菌体或菌根根尖的水提物提高了该联合芽孢杆菌的固氮酶活性，从而表明该细菌与结瘤菌根之间存在密切的营养关系。硫胺素比生物素更显著地提高细菌固氮酶的活性；对氨基苯甲酸检测不到细菌固氮酶的活性。即使按目前的方法测量，原位根瘤中的固氮酶活性水平很低，但它们可能对这些氮素有限的道格拉斯冷杉林长期的氮素动态做出了重大贡献。
Nitrogenase activities, measured by acetylene reduction, were detected under microaerophilic field conditions in Douglas-fir tuberculate ectomycorrhizae. Tuberculate ectomycorrhizae consist of densely packed clusters of ectomycorrhizal rootlets enclosed in a supplementary fungal peridium-like layer. Nitrogenase activity was primarily in the external layer and was greatly enhanced with added sucrose. The bacterium isolated, a nitrogen-fixing, spore-forming Bacillus sp., is an aerobe but requires anaerobic conditions for nitrogenase activity. Respiration in the tuberculate complex by the fungus. roots, and associated mycorrhizosphere microbes probably contributes to maintaining a microaerophilic niche where nitrogen fixation can take place. Water extracts of peridium or mycorrhizal root tips enhanced nitrogenase activity of this associative Bacillus sp., thereby indicating a close nutritional relationship between this bacterium and the tuberculate mycorrhizae. Thiamine more significantly enhanced bacterial nitrogenase activity than biotin; no activity was detected with p-aminobenzoic acid. Even though the levels of nitrogenase activities in the tubercles in situ were low, as measured by the present methods, they may indicate a significant contribution to the nitrogen dynamics of these nitrogen-limited Douglas-fir forests over a long-term period.