Background and aim

Nutrient availability plays a crucial role in both litter decomposition and decomposer communities. However, the specific effects of Epichloë endophytes on soil decomposer communities during the decomposition of their host litter under fertilized conditions are still unclear.

Methods

In this study, qPCR combined with Illumina sequencing was conducted to reveal the responses of functional gene communities involved in organic P recycling (phoD), nitrification (AOA/AOB-amoA), and denitrification (nirS/nirK) to Epichloë gansuensis-mediated decomposition of Achnatherum inebrians litter under different P addition treatments. Meanwhile, soil physicochemical properties and enzyme activities were measured.

Results

Both E. gansuensis infection and P addition exerted limited effect on the abundance and diversity of phoD-harboring microbial community. In the E. gansuensis-free (E−) samples, 60 mM P addition significantly increased the gene copies of AOA-amoA and significantly decreased those of AOB-amoA. Additionally, P addition decreased the richness and diversity of the nirK-harboring community in the E− samples, while E. gansuensis appeared to alleviate this response. P addition decreased the relative abundance of nirS-harboring Acidovorax and Azospirillum, while increasing the nirK-harboring Rhodopseudomonas and Bosea. Mantel’s test showed that E. gansuensis infection decreased the correlation between nitrifier communities and soil properties. Furthermore, nirS- and nirK-harboring communities showed a similar correlation pattern with soil properties in both E+ and E− soil samples.

Conclusions

This study demonstrates the important roles of E. gansuensis on nitrifier and denitrifier communities during its host grass decomposition under different P nutrient conditions, facilitating our comprehensive understanding of the ecological significance of Epichloë endophytes.

中文翻译：

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磷添加处理下硝化剂和反氮化剂群落对 Epichloë 内生菌介导的寄主凋落物分解的响应

 背景和目的

养分可用性在凋落物分解和分解群落中都起着至关重要的作用。然而，在施肥条件下，Epichloë 内生菌在其寄主凋落物分解过程中对土壤分解者群落的具体影响仍不清楚。

 方法

本研究采用 qPCR 结合 Illumina 测序，揭示了不同磷添加处理下有机磷循环 （phoD）、硝化 （AOA/AOB-amoA） 和反化作用 （nirS/nirK） 的功能基因群落对甘肃蕨介导的 Achnatherum inebrians 凋落物分解的响应。同时，测定土壤理化性质和酶活性。

 结果

E. gansuensis 感染和 P 添加对携带 phoD 的微生物群落的丰度和多样性的影响有限。在无甘蔗 （E-） 样品中，60 mM P 添加显著增加了 AOA-amoA 的基因拷贝，并显著降低了 AOB-amoA 的基因拷贝。此外，P 添加降低了 E− 样本中 nirK 携带群落的丰富度和多样性，而 E. gansuensis 似乎减轻了这种反应。P 添加降低了携带 nirS 的 Acidovorax 和 Azospirillum 的相对丰度，同时增加了携带 nirK 的 Rhodopseudomonas 和 Bosea。Mantel 的检验表明，甘肃桉虫感染降低了硝化菌群落与土壤特性之间的相关性。此外，nirS 和 nirK 携带群落与 E+ 和 E-土壤样品中的土壤特性表现出相似的相关模式。

 结论

本研究证明了不同磷养分条件下甘肃桉在寄主草分解过程中对硝化剂和反硝化剂群落的重要作用，有助于我们全面了解甘蔗内生菌的生态意义。