Timonen Sari, Hurek Thomas
Department of Applied Biology, P.O. Box 27, 00014 University of Helsinki, Finland.
Can J Microbiol. 2006 Aug;52(8):769-78. doi: 10.1139/w06-016.
Bacterial isolations were carried out on Pinus sylvestris--Suillus bovinus mycorrhizospheres obtained directly from boreal pine forest. When samples were taken during dry weather, the numbers of bacterial colony-forming units were significantly higher in uncolonized short roots and external mycelia than in mycorrhizal roots and soil outside the mycorrhizosphere. In contrast, the colony-forming unit counts were similar in all hypogeous samples after rainy weather. Culturable bacteria were absent from most Suillus bovinus sporocarps. The bacteria isolated from all types of mycorr hizo sphere samples, i.e. short roots, mycorrhizal roots, and external mycelia, consisted primarily of Burkholderia spp., whereas most isolates from soil outside the mycorrhizosphere were identified as Paenibacillus spp. This study shows that mycorrhizal external mycelia can expand the habitat favourable for common rhizosphere bacteria into the soil far from the immediate rhizosphere. Some of these bacteria may help the trees with nitrogen acquisition, since potentially diazotrophic bacteria harbouring nitrogenase reductase (nifH) genes were isolated from mycorrhizal root tips.
对直接取自北方松林的欧洲赤松——褐环乳牛肝菌菌根际进行了细菌分离。在干燥天气采集样本时，未被定殖的短根和外部菌丝体中的细菌菌落形成单位数量显著高于菌根根和菌根际以外的土壤中的数量。相比之下，雨后所有地下样本中的菌落形成单位计数相似。大多数褐环乳牛肝菌子实体中没有可培养细菌。从所有类型的菌根际样本（即短根、菌根根和外部菌丝体）中分离出的细菌主要是伯克霍尔德氏菌属，而从菌根际以外的土壤中分离出的大多数菌株被鉴定为类芽孢杆菌属。这项研究表明，菌根外部菌丝体可以将有利于常见根际细菌的栖息地扩展到远离直接根际的土壤中。其中一些细菌可能有助于树木获取氮，因为从菌根根尖分离出了携带固氮酶还原酶（nifH）基因的潜在固氮细菌。
