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Background and aims <p>Soil heterotrophic respiration (Rh) is critical for ecosystem carbon balance, but how microbial genomic adaptation to extreme drought across plant growth stages regulates Rh remains poorly understood. This study aimed to determine how drought-enriched bacteria adjust genome size, functional traits, and carbon acquisition capacity, and how these changes affect Rh in an alpine peatland.</p> Methods <p>We conducted a field extreme-drought manipulation experiment in an alpine peatland during the early, middle, and late plant growth stages. Metagenomic sequencing was used to identify drought-enriched bacteria and characterize their genome size, KEGG functional potential, drought-resistance genes, and carbon-acquisition-related genes. Soil hydrolytic enzyme activities and Rh were measured, and structural equation modeling was used to assess direct and indirect pathways regulating Rh.</p> Results <p>Drought-enriched bacteria consistently had smaller genomes than drought-depleted bacteria, supporting genome streamlining under drought stress. However, among drought-enriched groups, genome size and functional potential peaked in the middle stage, with genome size reaching 4.83 Mb compared with 4.04 Mb in the early stage and 3.66 Mb in the late stage. Under extreme drought, carbon-acquisition-related genes were most enriched in the middle stage, increasing by 15.8% relative to the early stage and by 9.8% relative to the late stage. Middle-stage drought-enriched bacteria also showed stronger drought-tolerance functions, including DNA repair, antioxidant defense, and osmoregulation. Notably, this genomic and functional peak coincided with the lowest hydrolytic enzyme activities, suggesting a mismatch between genomic potential and realized enzymatic processes. Structural equation modeling showed that microbial genetic traits had the greatest explanatory power for Rh in the middle stage.</p> Conclusions <p>Extreme drought selected for genome-streamlined bacteria in alpine peatland soils, but microbial adaptive strategies were strongly dependent on plant growth stage. Middle-stage drought-enriched bacteria retained greater functional potential and stronger drought-resistance and carbon-acquisition capacities, thereby modulating Rh under extreme drought. These findings highlight stage-dependent microbial eco-evolutionary strategies as key mechanisms regulating peatland carbon cycling under climate change.</p>

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Genome streamlining and functional adaptation of drought-enriched bacteria regulate soil heterotrophic respiration in alpine peatland

  • 期刊论文

  • 发表日期：

    2026年5月12日

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  • Yichang Gao,
  • Yong Li,
  • Zhongqing Yan,
  • Kerou Zhang,
  • Rongxiao Che,
  • Lizhen Cui,
  • Huan Wang,
  • Yuechuan Niu,
  • Enze Kang,
  • Weirong Zhuang,
  • Wenru Zhao,
  • Miaomiao An,
  • Xiaoming Kang

摘要

Background and aims

Soil heterotrophic respiration (Rh) is critical for ecosystem carbon balance, but how microbial genomic adaptation to extreme drought across plant growth stages regulates Rh remains poorly understood. This study aimed to determine how drought-enriched bacteria adjust genome size, functional traits, and carbon acquisition capacity, and how these changes affect Rh in an alpine peatland.

Methods

We conducted a field extreme-drought manipulation experiment in an alpine peatland during the early, middle, and late plant growth stages. Metagenomic sequencing was used to identify drought-enriched bacteria and characterize their genome size, KEGG functional potential, drought-resistance genes, and carbon-acquisition-related genes. Soil hydrolytic enzyme activities and Rh were measured, and structural equation modeling was used to assess direct and indirect pathways regulating Rh.

Results

Drought-enriched bacteria consistently had smaller genomes than drought-depleted bacteria, supporting genome streamlining under drought stress. However, among drought-enriched groups, genome size and functional potential peaked in the middle stage, with genome size reaching 4.83 Mb compared with 4.04 Mb in the early stage and 3.66 Mb in the late stage. Under extreme drought, carbon-acquisition-related genes were most enriched in the middle stage, increasing by 15.8% relative to the early stage and by 9.8% relative to the late stage. Middle-stage drought-enriched bacteria also showed stronger drought-tolerance functions, including DNA repair, antioxidant defense, and osmoregulation. Notably, this genomic and functional peak coincided with the lowest hydrolytic enzyme activities, suggesting a mismatch between genomic potential and realized enzymatic processes. Structural equation modeling showed that microbial genetic traits had the greatest explanatory power for Rh in the middle stage.

Conclusions

Extreme drought selected for genome-streamlined bacteria in alpine peatland soils, but microbial adaptive strategies were strongly dependent on plant growth stage. Middle-stage drought-enriched bacteria retained greater functional potential and stronger drought-resistance and carbon-acquisition capacities, thereby modulating Rh under extreme drought. These findings highlight stage-dependent microbial eco-evolutionary strategies as key mechanisms regulating peatland carbon cycling under climate change.