Biol Fert Soils:中科院吴金水研究组发表水稻光合碳的微生物利用机
2016年3月1日，在《BioLogy and Fertility of Soils》杂志上在线发表中科院亚热带农业生态研究所吴金水研究员领衔的农业生态过程方向研究团队在水稻光合碳的微生物利用机制方面取得了新研究进展文章，研究成果题为Microbial utilization of rice root exudates: 13C labeling and PLFA composition。审稿人和编辑认为“这是一个有趣和创新贡献的文稿;这个主题很有趣，因为相对于旱地土壤作物的根际沉积来说，在淹水条件下研究水稻根际沉积的研究则较少;该文稿的结果很有说服力。”
作物光合碳以根际沉积物的形式进入土壤，是根际微生物的主要碳源和能量来源。根际微生物能够通过自身代谢活动将这部分碳源或以气体的形式返回大气，或以有机质的形式存储于土壤中。根际微生物对光合碳的利用能够显著影响土壤碳固定过程。因此，水稻光合碳的输入及其微生物利用机制研究对于输入理解水稻根际土壤碳循环和碳固定过程具有重要意义。
基于此，该团队利用短时间(6小时)的碳同位素(13C-CO2)脉冲标记技术结合氯仿熏蒸的微生物量测定的经典方法与磷脂脂肪酸的稳定同位素探针技术(13C-PLFA-SIP)，发现水稻光合碳向土壤微生物生物量和磷脂脂肪酸组分快速转移的现象，揭示了真菌和革兰氏阴性菌是重要的光合碳的根际同化者，这两类微生物在水稻根际碳循环中起主要作用;同时水稻不同生育期光合碳的输入显著改变了水稻根际碳的微生物同化量及其群落结构，并且与水稻根系生物量呈极显著的正相关关系(图1)。该研究证明了土壤微生物活动与植物光合作用密切相关，为量化水稻土微生物量及其种群的动态变化提供了理论基础。
图1 水稻光合碳向土壤微生物生物量和磷脂脂肪酸组分快速转移
原文链接：
Microbial utilization of rICE root exudates: 13C labeling and PLFA composition
原文摘要：
The soluble components of rhizodeposition—root exudates—are the most important sources of readily available carbon (C) for rhizosphere microorganisms. The first steps of exudate utilization by microorganisms define all further flows of root C in the soil, including recycling and stabilization. Nevertheless, most studies have traced root exudates C much later after its initial uptake by microorganisms. To understand microbial uptake and utilization of rice root exudates, we traced 13C incorporated into microbial groups by 13C profiles of phospholipid fatty acids (PLFAs) within a short time (6 h) after 13CO2 pulse labeling. Labeling was conducted five times during three growth stages: active root growth (within the 21 days after transplanting), rapid shoot growth (37 and 45 days), and rapid reproduction (53 and 63 days). 13C was quickly assimilated throughout the rhizosphere microorganism, and the incorporation rate increased with rice maturity. Despite low redox conditions in paddy soil, fungi outcompeted bacteria in utilizing the root exudates. At all growth stages, fungal PLFAs (18:2 w6, 9c/18:0) showed the highest 13C levels, whereas actinomycete PLFAs (16:0 10-methyl) showed the lowest 13C incorporation. Principal component analysis revealed that the rhizosphere microbial community differed among rice growth stages, whereas the whole microbial community remained stable. In conclusion, the rapid incorporation of carbon from root exudates into microorganisms in paddy soils depends on the growth stage of the rice plant and is the first step of C utilization in rice rhizosphere, further defining C utilization and stabilization.
作者：吴金水
