Dip Diana, Constant Philippe
Centre Armand-Frappier Santé Biotechnologie, Institut national de la recherche scientifique, Université du Québec, Laval, Québec, Canada.
PeerJ. 2025 Sep 9;13:e20019. doi: 10.7717/peerj.20019. eCollection 2025.
N-fixing nodules release molecular hydrogen (H) in the rhizosphere of legumes. The process activates H-oxidizing bacteria (HOB) in soil, leading to multiple effects on biogeochemical processes and a potential biofertilization effect. The legacy effect of the energy potential of H on the soil microbial community structure and the population density of HOB has received little attention. The aim of the current study is to evaluate how the legacy effect of HOB, previously activated in soil microcosms exposed to elevated H concentrations (eH), affects biomass production yield of common vetch (), the abundance of HOB, and the composition of the rhizosphere microbiome.
Contrasting soil samples displaying more than 60% difference in H oxidation activity were used as growth substrate for vetch. Soil microbial community composition and diversity were examined by bacterial 16S rRNA polymerase chain reaction (PCR) amplicon sequencing, and dry weight (DW) of the above- and below-ground biomass of vetch was analyzed to assess the impact of HOB enrichment on plant growth. The population density of high-affinity HOB was estimated by using the droplet digital polymerase chain reaction (ddPCR) technique to target the gene, encoding for the large subunit of group 1H/5 [NiFe]-hydrogenase.
The abundance of HOB possessing group 1H/5 [NiFe]-hydrogenase was indistinguishable between the treatments, indicating that soil nutrient content (inorganic and organic carbon) and the energy potential of H were insufficient to support their growth. spp. and spp. were favored by eH exposure at the activation stage, but their response was lost after vetch growth. The root biomass and the root/shoot ratio were reduced in soil conditioned with eH compared to control soil exposed to ambient H, suggesting that the plant growth-promotion activity of HOB reduces root proliferation for nutrient prospection. These results provide new experimental evidence suggesting the biofertilization effect of H is not universal and requires specific conditions that are yet to be identified.
固氮根瘤在豆科植物根际释放分子氢（H）。这一过程会激活土壤中的氢氧化细菌（HOB），对生物地球化学过程产生多种影响，并具有潜在的生物施肥效应。H的能量潜力对土壤微生物群落结构和HOB种群密度的遗留效应很少受到关注。本研究的目的是评估先前在暴露于高浓度H（eH）的土壤微观世界中被激活的HOB的遗留效应如何影响普通野豌豆的生物量产量、HOB的丰度以及根际微生物组的组成。
使用H氧化活性差异超过60%的对比土壤样本作为野豌豆的生长基质。通过细菌16S rRNA聚合酶链反应（PCR）扩增子测序检测土壤微生物群落组成和多样性，并分析野豌豆地上和地下生物量的干重（DW），以评估HOB富集对植物生长的影响。通过使用液滴数字聚合酶链反应（ddPCR）技术靶向编码1H/5组[NiFe] - 氢化酶大亚基的基因，估计高亲和力HOB的种群密度。
各处理之间具有1H/5组[NiFe] - 氢化酶的HOB丰度没有差异，表明土壤养分含量（无机和有机碳）和H的能量潜力不足以支持它们的生长。在激活阶段，eH暴露有利于某些物种，但在野豌豆生长后它们的响应消失。与暴露于环境H的对照土壤相比，用eH处理的土壤中根生物量和根/茎比降低，这表明HOB促进植物生长的活性减少了用于养分勘探的根增殖。这些结果提供了新的实验证据，表明H的生物施肥效应并非普遍存在，需要特定条件，而这些条件尚未确定。
