Earthworm burrows: Kinetics and spatial distribution of enzymes of C-, N- and P- cycles
Earthworm burrows: Kinetics and spatial distribution of enzymes of C-, N- and P- cycles
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DOI：
10.1016/j.soilbio.2016.04.021
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发表时间：
2016-08-01
影响因子：
9.7
通讯作者：
Blagodatskaya, Evgenia
中科院分区：
文献类型：
--
作者：
Hoang, Duyen T. T.;Razavi, Bahar S.;Blagodatskaya, Evgenia
蚯蚓促进微生物活动，从而在土壤中产生热点。尽管蚯蚓的存在被认为改变了土壤酶系统，但蠕虫洞穴内酶活性的分布仍然未知。我们首次通过原位土壤酶谱分析了酶动力学并可视化了蠕虫洞穴（生物孔）内外的酶分布。在地龙形成的孔中测定了β-葡萄糖苷酶（GLU）、纤维二糖水解酶（CBH）、木聚糖酶（XYL）、几丁质酶（NAG）、亮氨酸氨肽酶（LAP）和酸性磷酸酶（APT）6种酶的动力学参数（V-max和K-m）。在蚯蚓洞穴中，GLU、NAG和APT的空间分布为在酶谱图像中可观察到。酶谱分析显示根际和蠕虫洞穴中热点的异质分布。洞穴中的热点区域比参考土壤（没有蚯蚓的土壤）大 2.4-14 倍。洞穴中 GLU、CBH、XYL、NAG 和 APT 的 V-max 值显着升高，证实了蚯蚓刺激了酶活性。对于 CBH、XYL 和 NAG，洞穴中的 K-m 值高出 2 至 3 倍，表明与参考土壤相比，不同的酶系统具有较低的底物亲和力。在底物浓度低于20 mu mol g(-1) 土壤时，CBH、XYL 和NAG 的K-m 增加抵消了蚯蚓对V-max 的积极影响。酶系统的变化反映了与参考土壤相比，优势微生物种群向对全纤维素和 N-乙酰氨基葡萄糖亲和力较低、对蛋白质亲和力较高的物种的转变。我们得出的结论是，蚯蚓洞穴是微生物热点，其酶活性比参考土壤更高且分布更密集。 (C) 2016 Elsevier Ltd. 保留所有权利。
Earthworms boost microbial activities and consequently create hotspots in soil. Although the presence of earthworms is thought to change the soil enzyme system, the distribution of enzyme activities inside worm burrows is still unknown. For the first time, we analyzed enzyme kinetics and visualized enzyme distribution inside and outside worm burrows (biopores) by in situ soil zymography. Kinetic parameters (V-max and K-m) of 6 enzymes - beta-glucosidase (GLU), cellobiohydrolase (CBH), xylanase (XYL), chitinase (NAG), leucine aminopeptidase (LAP) and acid phosphatase (APT) were determined in pores formed by Lumbricus terrestris L. In earthworm burrows, the spatial distributions of GLU, NAG and APT become observable in zymogram images. Zymography showed a heterogeneous distribution of hotspots in the rhizosphere and worm burrows. The hotspot areas were 2.4-14 times larger in the burrows versus reference soil (soil without earthworms). The significantly higher V-max values for GLU, CBH, XYL, NAG and APT in burrows confirmed that earthworms stimulated enzyme activities. For CBH, XYL and NAG, the 2- to 3-fold higher K-m values in burrows indicated different enzyme systems with lower substrate affinity compared to reference soil. The positive effects of earthworms on V-max were cancelled by the K-m increase for CBH, XYL and NAG at a substrate concentration below 20 mu mol g(-1) soil. The change of enzyme systems reflected a shift in dominant microbial populations toward species with lower affinity to holo-celluloses and to N-acetylglucosamine, and with higher affinity to proteins as compared to the reference soil. We conclude that earthworm burrows are microbial hotspots with much higher and denser distribution of enzyme activities than reference soil. (C) 2016 Elsevier Ltd. All rights reserved.