New Ecological Model Reveals How Nutrients Shape Vaginal Microbiome Health
Researchers affiliated with the Center for Advanced Microbiome Research and Innovation (CAMRI) have helped uncover a new way to understand one of the most persistent and challenging conditions in women’s health: bacterial vaginosis (BV). In a study published in PLOS Biology, an international team led by Dr. Samuel Alizon, Professor in the Centre for Interdisciplinary Research in Biology (CIRB) at the College de France in Paris, developed a mathematical model showing that the balance of nutrients in the vaginal environment, rather than bacteria alone, plays a decisive role in shaping whether the vaginal microbiome remains healthy or shifts into dysbiosis
BV affects nearly one in four women worldwide and is associated with discomfort, recurrent infection, increased risk of sexually transmitted infections, infertility, and adverse pregnancy outcomes. Despite its prevalence, BV remains notoriously difficult to treat, with high rates of recurrence even after antibiotic therapy.
From bacteria to resources
For more than a decade, vaginal microbiomes have been classified into distinct “community state types” (CSTs), ranging from Lactobacillus-dominated communities associated with vaginal health to diverse anaerobic communities linked to BV. What remains unclear is why these communities shift and why dysbiosis is so difficult to reverse.
The new study reframes the problem through the lens of ecological resource competition. The researchers focused on two classes of nutrients present in the vaginal environment:
• Shared resources, such as glycogen and its breakdown products, which can be used by many bacterial species and support Lactobacillus growth.
• Private resources, such as sialic acid derived from vaginal mucus, which can be exploited only by certain BV-associated bacteria, including Gardnerella vaginalis.
Using a mechanistic mathematical model, the team demonstrated that when private resources become abundant, BV-associated bacteria gain a competitive advantage, allowing them to dominate and stabilize dysbiotic communities. In contrast, environments rich in shared resources favor Lactobacillus-dominated, optimalmicrobiota
Why dysbiosis is hard to undo
One of the most striking insights from the model is the prediction of bistability (a system with two alternative stable states). Once the microbiome shifts toward a BV-associated state, simply removing symptoms or reducing bacterial load may not be enough to restore a healthy community. Instead, reversing dysbiosis may require a substantial change in the underlying nutrient landscape.
These predictions were supported by longitudinal clinical and metabolomic data from a North American cohort. The researchers found that transitions between healthy and dysbiotic microbiota closely tracked changes in the balance of shared versus private nutrients over time, confirming the model’s core predictions
New directions for prevention and treatment
In an accompanying PLOS Biology Primer, ecologist François Massol highlights how this resource-based framework opens new avenues for intervention. Rather than focusing solely on killing bacteria, future strategies could aim to reshape the vaginal nutrient environment, for example, by increasing glycogen availability to support Lactobacillus growth or limiting access to private resources that fuel BV-associated bacteria
This perspective aligns with emerging interest in synbiotics, vaginal live biotherapeutics, and non-antibiotic approaches to microbiome modulation. Importantly, the work also helps explain why many existing treatments are only temporarily effective: they fail to address the ecological conditions that stabilize dysbiosis.
International attention and broader impact
The study has already attracted international attention. In a feature article published in Le Monde, science journalist Pascale Santi described the work as a major step toward understanding the “fragile equilibrium” of the vaginal microbiome and the reasons recurrent BV remains so difficult to treat. The article emphasizes how nutrient competition, not just microbial composition, may be the key driver of vaginal health and disease
CAMRI’s role
Dr. Jacques Ravel, CAMRI Director, and Dr. Michael France, Research Associate at CAMRI, contributed clinical microbiome expertise and longitudinal data critical for testing and validating the model’s predictions. The study exemplifies CAMRI’s mission to integrate theory, data, and translational insight to advance microbiome-based solutions for human health.
By moving beyond descriptive microbiome profiling and toward mechanistic, predictive frameworks, this work sets the stage for next-generation interventions that are more durable, personalized, and biologically informed.