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Purpose <p>To understand the potential impacts of nitrogen (N) enrichment on soil microbial communities harboring the biomarker genes involved in denitrification, the variations in community structure and diversity of <i>nirS</i>-/<i>nirK</i>-type denitrifying bacteria were investigated in estuarine marsh soils.</p> Methods <p>A field experiment with four N enrichment levels (N<sub>0</sub>, no N addition treatment; N<sub>L</sub>, low N addition treatment; N<sub>M</sub>, medium N addition treatment; and N<sub>H</sub>, high N addition treatment) were conducted in <i>Cyperus malaccensis</i> marsh in the Min River estuary (Southeast China). After over 2 years of sustained N enrichment, the soils sampled from experimental plots were determined by high-throughput sequencing technique.</p> Results <p>Both Chao1 and Shannon indices of <i>nirS</i>-/<i>nirK</i>-type denitrifying bacterial communities in topsoil markedly declined with increasing N additions. The richness and diversity of <i>nirS</i>-type denitrifying bacterial communities in subsurface soil were higher than those of <i>nirK</i>-type communities, while the opposite trend was found in topsoil. Proteobacteria was the dominant denitrifying bacterial phylum in soil layers, with its relative abundance achieving the maximum in the N<sub>H</sub> treatment. The identified <i>nirS</i>-type denitrifying bacterial genera included Pseudomonas and Rhodanobacter, while <i>nirK</i>-type bacterial genera comprised Bradyrhizobium, Achromobacter, Sinorhizobium and Rhizobium. Over 50% of <i>nirS-</i>/<i>nirK</i>-type denitrifying bacteria in soils remained unclassified at both phylum and genus levels. The <i>nirS</i>-/<i>nirK</i>-type denitrifying bacterial genera responded differently to N enrichment, which rested with their ecological niche differentiation.</p> Conclusion <p>This paper found that sustained N enrichment significantly altered the composition of <i>nirS</i>-/<i>nirK</i>-type denitrifying bacterial communities in soils. Particularly, substantial unannotated or unclassified denitrifying bacterial communities emerged, with distinct vertical stratification in their differential responses to N enrichment.</p>

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Impacts of nitrogen enrichment on variations of nirS- and nirK-type denitrifying microbial communities in a typical subtropical estuarine marsh, Southeast China

  • 期刊论文

  • 发表日期：

    2026年3月21日

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  • Guanrong Fang,
  • Zhigao Sun,
  • Yajin Li,
  • Huihui Wu,
  • Erheng Li,
  • Bingbing Chen

摘要

Purpose

To understand the potential impacts of nitrogen (N) enrichment on soil microbial communities harboring the biomarker genes involved in denitrification, the variations in community structure and diversity of nirS-/nirK-type denitrifying bacteria were investigated in estuarine marsh soils.

Methods

A field experiment with four N enrichment levels (N0, no N addition treatment; NL, low N addition treatment; NM, medium N addition treatment; and NH, high N addition treatment) were conducted in Cyperus malaccensis marsh in the Min River estuary (Southeast China). After over 2 years of sustained N enrichment, the soils sampled from experimental plots were determined by high-throughput sequencing technique.

Results

Both Chao1 and Shannon indices of nirS-/nirK-type denitrifying bacterial communities in topsoil markedly declined with increasing N additions. The richness and diversity of nirS-type denitrifying bacterial communities in subsurface soil were higher than those of nirK-type communities, while the opposite trend was found in topsoil. Proteobacteria was the dominant denitrifying bacterial phylum in soil layers, with its relative abundance achieving the maximum in the NH treatment. The identified nirS-type denitrifying bacterial genera included Pseudomonas and Rhodanobacter, while nirK-type bacterial genera comprised Bradyrhizobium, Achromobacter, Sinorhizobium and Rhizobium. Over 50% of nirS-/nirK-type denitrifying bacteria in soils remained unclassified at both phylum and genus levels. The nirS-/nirK-type denitrifying bacterial genera responded differently to N enrichment, which rested with their ecological niche differentiation.

Conclusion

This paper found that sustained N enrichment significantly altered the composition of nirS-/nirK-type denitrifying bacterial communities in soils. Particularly, substantial unannotated or unclassified denitrifying bacterial communities emerged, with distinct vertical stratification in their differential responses to N enrichment.