Yarwood Stephanie A, Myrold David D, Högberg Mona N
Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA.
FEMS Microbiol Ecol. 2009 Oct;70(1):151-62. doi: 10.1111/j.1574-6941.2009.00733.x. Epub 2009 Jun 25.
The introduction of photosynthates through plant roots is a major source of carbon (C) for soil microbial biota and shapes the composition of fungal and bacterial communities in the rhizosphere. Although the importance of this process, especially to ectomycorrhizal fungi, has been known for some time, the extent to which plant belowground C allocation controls the composition of the wider soil community is not understood. A tree-girdling experiment enabled studies of the relationship between plant C allocation and microbial community composition. Girdling involves cutting the phloem of trees to prevent photosynthates from entering the soil. Four years after girdling, fungal and bacterial communities were characterized using DNA-based profiles and cloning and sequencing. Data showed that girdling significantly altered fungal and bacterial communities compared with the control. The ratio of ectomycorrhizal to saprobic fungal sequences significantly decreased in girdled treatments, and this decline was found to correlate with the fungal phospholipid fatty acid biomarker 18:2omega6,9. Bacterial communities also varied in the abundance of the two dominant phyla Acidobacteria and Alphaproteobacteria. Concomitant changes in fungal and bacterial communities suggest linkages between these two groups and point toward plant belowground C allocation as a key determinant of microbial community composition.
通过植物根系引入光合产物是土壤微生物生物群碳（C）的主要来源，并塑造了根际真菌和细菌群落的组成。尽管这一过程的重要性，尤其是对外生菌根真菌的重要性，已经为人所知一段时间了，但植物地下碳分配对更广泛土壤群落组成的控制程度尚不清楚。一项环割树木的实验使得对植物碳分配与微生物群落组成之间的关系进行研究成为可能。环割涉及切割树木的韧皮部，以防止光合产物进入土壤。环割四年后，使用基于DNA的图谱以及克隆和测序对真菌和细菌群落进行了表征。数据表明，与对照相比，环割显著改变了真菌和细菌群落。在外生菌根真菌与腐生真菌序列的比率在环割处理中显著下降，并且发现这种下降与真菌磷脂脂肪酸生物标志物18:2ω6,9相关。细菌群落中两个优势门酸杆菌门和α-变形菌门的丰度也有所不同。真菌和细菌群落的伴随变化表明这两组之间存在联系，并指出植物地下碳分配是微生物群落组成的关键决定因素。
