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Background and aims <p>Prickly pear cactus (<i>Nopalea cochenillifera</i> L.) plays a central role in sustaining forage production in semiarid environments, yet prolonged drought associated with climate change increasingly constrains its performance. Plant growth-promoting bacteria (PGPB), including <i>Bacillus subtilis</i> and <i>Paenibacillus</i> spp., are recognized for enhancing plant tolerance to water limitation, but their influence on the rhizosphere microbiome of cactus under drought conditions remains unclear. We tested whether inoculation with these bacteria shapes rhizosphere bacterial community composition and interaction patterns under water deficit.</p> Methods <p>A greenhouse experiment was conducted using a factorial design combining two water regimes (well-watered and water-deficit) with three inoculation treatments (<i>B. subtilis</i>, <i>Paenibacillus</i> sp., and a non-inoculated control). After 150&#xa0;days of water stress exposure, rhizosphere bacterial communities were assessed using 16S rRNA gene amplicon sequencing.</p> Results <p>Water availability was the dominant driver of rhizosphere bacterial community structure, with drought favoring Actinobacteriota and well-watered conditions enriching Proteobacteria. Inoculation with <i>B. subtilis</i> modified community composition and increased the prevalence of drought-associated taxa, while also promoting a higher proportion of positive microbial interactions under water deficit. In contrast, <i>Paenibacillus</i> sp. exerted weaker and more variable effects. Despite microbial shifts, inoculation did not significantly affect plant biomass or root traits.</p> Conclusions <p>Rhizosphere bacterial communities of prickly pear cactus are primarily structured by water availability, whereas PGPB inoculation induces secondary, taxa-specific effects. Under drought, <i>B. subtilis</i> enhances microbial network connectivity, suggesting that inoculants may influence rhizosphere functioning even when plant growth responses are limited.</p>

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Inoculation with Bacillus subtilis and Paenibacillus sp. shapes the rhizosphere bacteriome of prickly pear cactus under water deficit

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月20日

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  • Rhaiana Oliveira de Aviz,
  • Janaira Rocha Campos,
  • Marcos Renan Lima Leite,
  • Sandra Mara Barbosa Rocha,
  • Maria Helena Ferreira Duarte,
  • Pâmalla Graziely Carvalho Moraes,
  • Gonçalves Albino Dauala,
  • Elaine Martins da Costa,
  • Rafael de Souza Miranda,
  • Cacio Luiz Boechat,
  • Arthur Prudêncio de Araujo Pereira,
  • Erika Valente de Medeiros,
  • Lucas William Mendes,
  • Ademir Sérgio Ferreira Araujo

摘要

Background and aims

Prickly pear cactus (Nopalea cochenillifera L.) plays a central role in sustaining forage production in semiarid environments, yet prolonged drought associated with climate change increasingly constrains its performance. Plant growth-promoting bacteria (PGPB), including Bacillus subtilis and Paenibacillus spp., are recognized for enhancing plant tolerance to water limitation, but their influence on the rhizosphere microbiome of cactus under drought conditions remains unclear. We tested whether inoculation with these bacteria shapes rhizosphere bacterial community composition and interaction patterns under water deficit.

Methods

A greenhouse experiment was conducted using a factorial design combining two water regimes (well-watered and water-deficit) with three inoculation treatments (B. subtilis, Paenibacillus sp., and a non-inoculated control). After 150 days of water stress exposure, rhizosphere bacterial communities were assessed using 16S rRNA gene amplicon sequencing.

Results

Water availability was the dominant driver of rhizosphere bacterial community structure, with drought favoring Actinobacteriota and well-watered conditions enriching Proteobacteria. Inoculation with B. subtilis modified community composition and increased the prevalence of drought-associated taxa, while also promoting a higher proportion of positive microbial interactions under water deficit. In contrast, Paenibacillus sp. exerted weaker and more variable effects. Despite microbial shifts, inoculation did not significantly affect plant biomass or root traits.

Conclusions

Rhizosphere bacterial communities of prickly pear cactus are primarily structured by water availability, whereas PGPB inoculation induces secondary, taxa-specific effects. Under drought, B. subtilis enhances microbial network connectivity, suggesting that inoculants may influence rhizosphere functioning even when plant growth responses are limited.