The spatial distribution of alkaline phosphomonoesterase (ALP) activity in the rhizosphere and bulk soil of three plants ( Zea mays , Medicago sativa , and Cyperus rotundus ) grown in a karst soil (pH 8.27) was visualized using in situ soil zymography. According to the zymogram images, we identified and precisely collected soil samples from hotspots and non-hotspots of ALP activity, and then analyzed the phoD genes that encoded alkaline phosphomonoesterase and assessed the microbial community. The results showed that (1) the phoD abundance in the plant types varied and was highest in the alfalfa and lowest in the maize; (2) Proteobacteria dominated the phoD -harboring microbes in the rhizosphere and Actinobacteria dominated the phoD -harboring microbes in the bulk soil, and (3) the ALP activity was positively correlated with the relative abundance of the diazotrophic Azotobacter , but negatively correlated with the phoD gene abundance, microbial community richness, and diversity. By coupling zymography and microbial molecular approaches, we identified hotspots of enzymatic and microbial activity in rhizosphere soil and evaluated the relative contributions from potential active microorganisms. We found that the function of specific phoD -harboring microorganisms in these hotspots differed depending on the plant in the soil, which had implications for phosphorus (P) management in P-limited karst soils. The results also suggested that free-living N 2 -fixing bacteria ( Azotobacter ) might promote ALP activity, thereby emphasizing vital linkages between, and coupling of, the soil nutrient cycles.

中文翻译：

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稀有微生物分类群而不是phoD基因丰度决定了岩溶根际土壤中碱性磷酸单酯酶活性的热点

碱性磷酸单酯酶 (ALP) 活性在岩溶土壤 (pH 8.27) 中生长的三种植物（玉米、苜蓿和香附）的根际和大块土壤中的空间分布使用原位土壤酶谱进行可视化。根据酶谱图像，我们从 ALP 活动的热点和非热点中识别并精确收集土壤样品，然后分析编码碱性磷酸单酯酶的 phoD 基因并评估微生物群落。结果表明：（1）不同植物类型的phoD丰度存在差异，紫花苜蓿最高，玉米最低；(2) 变形菌在根际占 phoD 的微生物占主导地位，而放线菌在大块土壤中占 phoD 的存留微生物，(3) ALP活性与固氮菌相对丰度呈正相关，与phoD基因丰度、微生物群落丰富度和多样性呈负相关。通过结合酶学和微生物分子方法，我们确定了根际土壤中酶促和微生物活动的热点，并评估了潜在活性微生物的相对贡献。我们发现这些热点中特定 phoD 携带微生物的功能因土壤中的植物而异，这对限磷喀斯特土壤中的磷 (P) 管理有影响。结果还表明，自由生活的 N 2 固定细菌（固氮菌）可能会促进 ALP 活性，从而强调土壤养分循环之间的重要联系和耦合。