Distinct response of rare and abundant microorganisms to salinity stress in rhizosphere soil: Community assembly, functional potential and network interaction

Le résumé fourni par la source

Abundant and rare taxa exhibit distinct functional traits that sustain ecosystem stability under soil salinization. However, most studies on salt-adaptation strategies of rhizosphere microbiota have focused on the whole community, with little attention to the differences between these subcommunities. To address this issue, we conducted a maize mesocosm experiment using Calcaric Fluvisol under low, medium, and high salinity levels, and investigated the co-occurrence, assembly, and functional potentials of these subcommunities via 16S ribosomal DNA (16S rDNA) and internal transcribed spacer (ITS) amplicon sequencing. Results showed that deterministic assembly processes intensified with soil salinity, leading to the enrichment of halotolerant copiotrophic genera (e.g., Pseudomonas and Sphingomonas ). Consequently, α-diversity increased in abundant bacteria while rare bacterial diversity remained unchanged. Conversely, fungi exhibited the opposite pattern for the two taxa. Functional prediction revealed that the proliferation of abundant bacteria was linked to a highly efficient osmotic adjustment strategy centered on lipid and cofactor/vitamin metabolism, whereas rare bacteria adopted low-energy carbohydrate strategies. In contrast, abundant fungi favored carbohydrate metabolism and rare taxa depended more on lipid metabolism. Notably, salinity weakened network complexity, stability, and closeness centrality in rare-dominated networks for both bacteria or fungi, which coincided with reduced internal connectivity, increased cross-links to abundant taxa, and keystone shifts toward halotolerant abundant taxa. Multispectral analysis of dissolved organic matter (DOM) chemodiversity further revealed that salinity-enriched fulvic-like compounds with low aromaticity correlated significantly with abundant taxa but weakly with rare taxa. In summary, this study provides important evidence for divergent evolutionary strategies between abundant and rare biospheres, spanning community assembly, metabolic optimization, and network interactions.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.