In the hidden world beneath our feet and within our bodies, a complex web of life is constantly evolving — shaping and reshaping ecosystems in ways we are only beginning to understand. Recent advances in microbiome research have uncovered a captivating narrative interlinking the soil, plants, and the human gut, revealing an intricate axis of microbial exchange and co-evolution. This soil-plant-human gut microbiome axis not only challenges traditional perspectives but also opens new pathways to reevaluate how microbial communities influence our health, agriculture, and environment.
At the heart of this dynamic system lies the phenomenon of co-evolution, where species originating from distinct lineages reciprocally influence each other’s evolutionary trajectories. This biological dance results in intricate ecological relationships that profoundly affect phenotypes across ecosystems. In the context of the soil-plant-human continuum, the soil acts as a massive microbial reservoir teeming with diverse bacterial taxa. Among these, certain bacteria like Helicobacter pylori exemplify the fluidity of microbial existence, transferring from soil habitats to the human gut through pathways such as contaminated food or irrigation with wastewater.
Strikingly, genomic analyses have shown that H. pylori strains residing in soil environments share 96% to 100% nucleotide sequence homology with those found in the human gastrointestinal tract. This highlights a close genetic relationship, suggesting ongoing exchanges and adaptation between these habitats. The bacterium’s genomic plasticity, characterized by frequent intraspecific recombination events, equips it with the adaptability necessary to colonize the human gut even under selective pressures such as antibiotic treatments. This plasticity fosters the emergence of diverse resistance profiles, including those conferring multidrug resistance, which presents increasing challenges in medical therapeutics.
Yet, this microbial interplay does not end within human hosts. Resistance genes, once selected under medical antibiotic pressure, can re-enter soil environments, perpetuating a cycle of selection and adaptation. Soil-borne H. pylori populations may thus acquire and disseminate these resistance determinants, increasing the risk of resistant infections in humans. This bidirectional flow of genetic material illustrates the profound interconnectedness of microbiomes across ecosystems, implicating human interventions in shaping soil microbial communities and vice versa.
Pseudomonas species offer a second compelling example of this reciprocal influence along the axis. Renowned for their ubiquity and metabolic versatility, Pseudomonas bacteria thrive in diverse habitats, employing broad repertoires of organic and inorganic compounds as energy sources. Their remarkable resilience stems not only from this metabolic adaptability but also from their ability to form protective biofilms — complex microbial aggregates that shield the cells from adverse environmental conditions, including antimicrobial agents.
The genetic landscape of Pseudomonas is further marked by genomic plasticity amplified through horizontal gene transfer (HGT). This mechanism enables these bacteria to continuously acquire and distribute advantageous traits such as antibiotic resistance genes and toxin factors. Through biofilm-mediated gene exchange, Pseudomonas can rapidly evolve functions tailored to survival in soil, plant, and human-associated niches, thereby orchestrating functional shifts within microbial communities along the soil-plant-human continuum.
Understanding the mechanisms that govern such reciprocal microbial effects demands exploration beyond mere presence or absence of specific bacteria. The proposed conceptual framework encompasses foundational processes such as molecular mimicry, horizontal gene transfer, cross-feeding interactions, and host selection, all of which contribute to the co-evolution of microbial communities.
Molecular mimicry, for instance, provides bacteria with the ability to imitate host molecules, a strategy that can modulate host immune responses and facilitate persistent colonization. In the soil-plant-human gut axis, this may allow microbes to traverse across boundaries with reduced immune detection. Horizontal gene transfer stands as a cornerstone in microbial evolution, enabling not only the rapid acquisition of resistance traits but also the sharing of metabolic pathways that broaden ecological niches.
Cross-feeding interactions represent another layer of microbial cooperation and competition, where metabolic byproducts from one species serve as resources for another. Such nutrient exchanges sustain complex microbial assemblages both in the rhizosphere — the soil region influenced by root secretions — and in the human gut, shaping community structure and function.
Host selection mechanisms further refine these interactions by imposing selective pressures that shape microbial consortia. Plant roots secrete exudates that selectively nurture beneficial microbes, while the human gastrointestinal environment selects for bacteria suited to its unique conditions. The interplay of these selection forces can drive evolutionary convergence and divergence within respective microbiomes.
Collectively, these mechanisms create a dynamic ecology where microbes not only survive but co-adapt across interconnected environments. The soil is no longer merely a passive reservoir; rather, it is an active participant in shaping microbial traits that ripple through plant communities and eventually influence human health.
Beyond fundamental biology, deciphering this soil-plant-human gut microbiome axis holds profound implications for agriculture and medicine. For instance, unraveling how agricultural practices impact soil microbial communities could inform sustainable farming strategies that optimize plant health while mitigating the spread of antibiotic resistance. Similarly, understanding the microbial crosstalk that emerges from environmental reservoirs can aid in predicting and controlling zoonotic or environmental pathogens.
Moreover, the resilience of bacterial taxa like H. pylori and Pseudomonas underscores the challenges in combating antibiotic resistance. Their ability to shuttle genetic material across ecosystems highlights the need for integrated approaches addressing both clinical and environmental reservoirs. The bidirectional flow of resistance genes emphasizes that antibiotic stewardship must transcend hospital walls and encompass ecological contexts.
Moving forward, emerging tools in metagenomics, single-cell genomics, and synthetic biology promise to uncover nuanced interactions within the soil-plant-human axis. These approaches will elucidate how microbial communities assemble, respond to disturbances, and evolve functionally over time. Integrating ecological data with evolutionary theory will further enhance our capacity to predict microbial dynamics and their impacts on ecosystem services.
The recognition of this axis also redefines human health in a broader ecological framework. It invites a paradigm shift towards a more holistic “One Health” perspective where human, plant, and environmental microbiomes are interconnected pillars sustaining life and well-being. The revelation that microbes circulating among soil, plants, and humans collectively shape health and disease exemplifies the complexity and beauty of life’s microscopic networks.
In essence, the soil-plant-human gut microbiome axis is more than a scientific curiosity; it is a testament to the fundamental interconnectedness of life. This microbial continuum transcends traditional boundaries, urging us to rethink how ecosystems interact and how human activities reverberate across the biosphere at the microbial level.
As we deepen our understanding of these co-evolutionary processes, we stand at the threshold of harnessing microbiomes as allies in addressing global challenges — from food security and sustainable agriculture to antimicrobial resistance and human health. The soil beneath us, the plants we cultivate, and the microbes residing within us together compose a symphony of interactions, evolving side by side in a delicate balance shaped by genetics, environment, and time.
Illuminating this axis will require a concerted interdisciplinary effort, uniting microbiologists, ecologists, clinicians, and agricultural scientists. By embracing the complexity and embracing the multiplicity of microbial life, we can unlock new potentials for innovation grounded in the shared evolutionary trajectories of life on Earth.
Subject of Research: The interaction and co-evolution of microbial communities across the soil, plant, and human gut microbiomes, focusing on mechanisms that drive reciprocal evolutionary effects.
Article Title: The soil-plant-human gut microbiome axis into perspective.
Article References:
Ma, H., Cornadó, D. & Raaijmakers, J.M. The soil-plant-human gut microbiome axis into perspective. Nat Commun 16, 7748 (2025). https://doi.org/10.1038/s41467-025-62989-z
Image Credits: AI Generated
