Editorial: Bacteria’s role in soil health and microbiomes

Soil microorganisms play a significant role in agroecosystem functioning, driving nutrient cycling, supporting plant health, and maintaining ecosystem stability, especially as environmental pressures increase (Hassan-Dalléac et al., 2026). Among these, plant-microbiome interactions are particularly influential, mobilising nutrients, regulating plant hormonal pathways, modifying soil structure, and protecting crops against stress (Kumari et al., 2023; Trivedi et al., 2020). Despite these advances, many microbiome studies remain descriptive, focusing on cataloguing microbial diversity without elucidating the underlying mechanisms (Hartmann and Six, 2023). Developing a mechanistic understanding of how bacteria contribute to soil function and crop performance, both at the level of individual strains and entire communities is therefore critical to achieving sustainable agriculture.

The articles in this Research Topic improve our understanding of microbiome function by integrating genomic data with ecological context across farming systems and environments. Zhang et al. characterise Stenotrophomonas rhizophila T3E, a multifunctional rhizobacterium, isolated from tomato rhizosphere soil. Inoculation with T3E significantly enhanced root development, modulated phytohormones including indole-3-acetic acid and abscisic acid, strengthened antioxidant systems, and upregulated multiple root development genes. The T3E isolate also transformed the soil environment, improving total nitrogen, total and available phosphorus, and available potassium levels, while significantly enhancing the activities of phosphatase, urease, catalase, and sucrase, which are central to nutrient cycling and organic matter decomposition. Combining whole-genome sequencing with physiological and biochemical measurements, the authors provide evidence that single strains can influence multiple plant and soil parameters and support proposed mechanisms through direct experimental evidence.

Phosphorus remains one of the most persistent limitations to global crop productivity. However, most soil phosphorus exists in forms that are poorly available to plants, and the overuse of phosphate fertilisers to compensate for this limitation carries significant environmental costs (Zou et al., 2022). Shayanthan et al. address this challenge by characterising phosphate-solubilising Paraburkholderia strains from agricultural soils, demonstrating their ability to enhance early soybean growth. By integrating plant growth-promotion assays with complete genome sequencing, the study revealed the presence of a complete Calvin-Benson-Bassham pathway, which is a key metabolic route for carbon fixation that is not commonly associated with this taxon. The authors also uncovered substantial strain-level genomic and metabolic variation. The findings emphasise that relying solely on taxonomic identity is rarely sufficient to predict specific function, and that effective bioinoculants should be locally adapted, identified at the strain level, and tested under realistic soil conditions.

The long-term field experiment by Cerecetto et al. in the Uruguayan Pampa provides compelling evidence that farming system design can influence microbiome composition and function. Spanning a gradient of land use intensities from continuous cropping to natural grassland, the study shows that extended pasture phases sustain soil organic carbon, nitrogen pools, and microbial functional indicators. Microbial community composition, rather than alpha-diversity, emerged as a strong predictor of soil functionality and crop performance (Zhu et al., 2022). Pasture-based systems preferentially enriched genera such as Streptomyces, Pseudomonas, Bacillus, and Microbacterium, many of which expressed multiple plant-beneficial traits. A key factor here is managed soil legacy, the long-lasting influence of past management on microbial community structure and function (Idbella et al., 2024). The persistence of a pasture-derived microbial legacy years after pasture removal, and its capacity to support subsequent crop performance, may have practical implications for other mixed crop-livestock systems.

Rigerte et al. developed and tested a drought-tolerant synthetic microbial community, DT-SynCom, to improve barley performance under water stress. Sixteen bacterial strains were isolated from barley rhizospheres exposed to simulated future climate conditions and selected based on drought tolerance, rhizosphere enrichment, and plant growth-promoting characteristics. Composed of Actinobacteria, Proteobacteria, and Firmicutes, the consortium reduced leaf wilting and improved barley performance. Genome-resolved analyses, combined with trait screening, revealed complementary functional capacities across the strains including ACC deaminase activity, auxin biosynthesis, phosphate solubilisation, siderophore production, and osmoprotectant pathways, highlighting the functional advantages of community-level microbial design. The DT-SynCom was assembled using ecological filters, selecting strains based on environmental relevance and functional traits rather than arbitrary criteria, demonstrating an ecologically informed SynCom design that bridges controlled experimental systems with field-relevant microbial selection.

A consistent pattern across the four articles is that bacterial contributions to soil health are context dependent. Soil type, climate, cropping system, and management history all determine which microbial functions are expressed or suppressed, suggesting the need for locally sourced microbial strains over generalist inoculant mixes. Function, rather than diversity alone, may be more strongly associated with soil health and crop performance. Integrating genomic and phenotypic evidence is therefore essential: genome-resolved analyses reveal metabolic potential, while realised function can only be determined when combined with trait assays, plant responses, and soil measurements.

A major challenge remains in translating microbiome discoveries from controlled environments into reliable field applications. Both synthetic communities and single-strain inoculants must establish and function within resident soil microbiomes (Armanhi et al., 2021), and benefits observed under controlled conditions often do not translate to complex field environments (Russ et al., 2023). Regulatory frameworks for microbial biofertilizers continue to lag behind scientific advances in many jurisdictions, and questions of equitable access remain inadequately addressed (Fadiji et al., 2024). Small-scale farmers, who stand to benefit the most from reduced reliance on synthetic inputs, still face barriers to adoption and deserve greater attention from researchers and policymakers.

Long-term field trials and multi-environment experiments are essential to determine the persistence, robustness, and scalability of microbiome-mediated benefits under realistic field conditions (De Vries et al., 2020). Targeted exclusion and reassembly experiments within synthetic communities will be crucial for identifying keystone taxa, functional redundancy, and interaction networks that underpin system stability. Pasture-based rotations that sustain organic matter inputs and maintain microbial habitat continuity may help plants recruit beneficial microbiota and enhance system resilience (Berendsen et al., 2012).

In summary, the articles assembled here demonstrate that bacterial contributions to soil health are driven by interacting traits, communities, and management legacies rather than isolated microbes or short-term interventions alone. By advancing function-driven, genome-informed, and ecologically contextualised research, the studies featured here set the direction for future soil microbiome research and its application in sustainable, climate-resilient agroecosystems.

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Footnotes

Edited and reviewed by: Holger Heuer, Julius Kühn-Institut, Germany