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<p>Free-living (FL) and particle-associated (PA) bacteria represent ecologically distinct fractions in freshwater microbiomes, yet their dynamics across river–reservoir continua remain poorly understood. We investigated these assemblages in Lake Qiandaohu to elucidate differences in their diversity, composition, function, and network organization. PA communities consistently exhibited higher <i>α</i>-diversity, reflecting the enhanced niche availability within organic aggregates, whereas FL assemblages showed higher sensitivity to nutrient gradients. Although <i>β</i>-diversity revealed clear niche partitioning, both fractions were governed by similar environmental drivers, with FL communities exhibiting a stronger dependence on bulk-water chemistry. Taxonomic and functional analyses revealed divergent lifestyle strategies: FL communities were dominated by oligotrophic lineages (e.g., <i>hgcI clade</i>), whereas the PA fraction was enriched with taxa specialized in particle degradation and biofilm formation. Network analyses demonstrated that FL assemblages formed densely connected but structurally fragile networks. Conversely, PA networks exhibited higher modularity and robustness, suggesting more resilient organization. Functional predictions highlighted contrasting stress-response mechanisms, further underscoring distinct resilience thresholds. Collectively, these findings demonstrate that FL–PA partitioning is a conserved ecological pattern shaped by microhabitat heterogeneity and nutrient availability. Their complementary roles emphasize the necessity of considering both fractions to fully understand microbial stability and biogeochemical cycling in reservoirs.</p>

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Ecological partitioning of free-living and particle-associated bacteria reveals complementary strategies in a river–reservoir continuum

  • 期刊论文

  • 发表日期：

    2026年1月21日

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  • Guijuan Xie,
  • Chen Wang,
  • Xinyu Chen,
  • Zhen Shen,
  • Xuejun Wang,
  • Zhichao Yin,
  • Yi Gong,
  • Hai Xu,
  • Xiangming Tang

摘要

Free-living (FL) and particle-associated (PA) bacteria represent ecologically distinct fractions in freshwater microbiomes, yet their dynamics across river–reservoir continua remain poorly understood. We investigated these assemblages in Lake Qiandaohu to elucidate differences in their diversity, composition, function, and network organization. PA communities consistently exhibited higher α-diversity, reflecting the enhanced niche availability within organic aggregates, whereas FL assemblages showed higher sensitivity to nutrient gradients. Although β-diversity revealed clear niche partitioning, both fractions were governed by similar environmental drivers, with FL communities exhibiting a stronger dependence on bulk-water chemistry. Taxonomic and functional analyses revealed divergent lifestyle strategies: FL communities were dominated by oligotrophic lineages (e.g., hgcI clade), whereas the PA fraction was enriched with taxa specialized in particle degradation and biofilm formation. Network analyses demonstrated that FL assemblages formed densely connected but structurally fragile networks. Conversely, PA networks exhibited higher modularity and robustness, suggesting more resilient organization. Functional predictions highlighted contrasting stress-response mechanisms, further underscoring distinct resilience thresholds. Collectively, these findings demonstrate that FL–PA partitioning is a conserved ecological pattern shaped by microhabitat heterogeneity and nutrient availability. Their complementary roles emphasize the necessity of considering both fractions to fully understand microbial stability and biogeochemical cycling in reservoirs.