The Probiotic Designed To Work When Your Gut Is Under Attack
Conventional probiotics often fail during stress or flare-ups – just when support is most needed.
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The gut microbiome plays a pivotal role in maintaining human health, influencing everything from digestion to immune function. However, conventional probiotics frequently fail to deliver results when the gut is under stress or inflamed – precisely when effective support is most critical.
Specializing in next-generation probiotics, Ferryx, a spin-out company from the University of Bristol, is pioneering a novel approach to gut health. Ferryx has developed a probiotic designed to function in hostile gut environments, like those seen in irritable bowel syndrome (IBS) flare-ups and inflammatory bowel conditions.
Following the BioTrinity 2025 conference, Technology Networks spoke with Dr. Jenny Bailey Cooper, co-founder and CEO of Ferryx, to learn the science behind its lead product, Ferrocalm™, the iron-responsive strain FX856 and how its innovative strategy could reshape the future of gut health treatment.
How stress impacts gut health
To understand why traditional probiotics do not work in flare ups or conditions of stress, it is important to understand the physiology behind how stress impacts gut health.
The gut—brain axis describes the direct, two-way communication pathway between the gut and the brain. Feeling butterflies in your stomach before an important event or when you are nervous is a clear example of this connection. Bailey Cooper explains in situations of stress, hormones (e.g., cortisol) and neurotransmitters can disrupt this gut—brain communication: “These disruptions can affect gut motility – how quickly food moves through the digestive tract – leading to symptoms like bloating, abdominal pain, diarrhea and constipation, all common in conditions like IBS.”
“The nerves in the gut can also become hypersensitive under stress, firing unnecessarily and triggering painful spasms. Stress may also alter gut secretions, which can further contribute to symptoms like diarrhea. Another key issue is increased gut permeability – commonly referred to as ‘leaky gut’ – which can promote low-grade inflammation,” she continued.
The effects of stress also go beyond the gut itself.
“The gut microbiome – the vast community of bacteria living in the digestive system – is also highly sensitive to stress. Chronic stress can elevate cortisol levels, which in turn alters the composition and function of the microbiome,” said Bailey Cooper. “While stress can impact anyone’s digestive health, its effects are often more pronounced in people with IBS or inflammatory bowel disease. In these cases, the impact of stress on the gut can be especially significant.”
Traditional probiotics often fail during flare-ups or stressful environments
A stressed or inflamed gut creates a hostile environment for most conventional probiotics, which points to excessive iron levels in the gut. “This can happen for a few reasons,” explained Bailey Cooper. “Inflammation might cause bleeding into the gut, and stress hormones can both release iron from storage and block its absorption into the body. As a result, you get a buildup of iron in the gut lumen.”
While most of the gut microbiome can use iron as a growth factor, thriving under high-iron conditions, many species used in conventional probiotics, like Lactobacilli and Bifidobacteria, are quite unusual – they can’t use iron to grow. “They struggle to compete for nutrients and are easily outcompeted in inflamed or iron-rich environments. They can’t survive, so they can’t deliver any beneficial effect.”
Although presenting initially as a challenge, Bailey Cooper and the team took this as an opportunity to address unmet research needs.
“First, we identified candidate probiotic strains that increase their growth rate in response to iron – so they’re suited to the exact environment where they're needed most. From there, we applied a rational screening process to find strains with additional beneficial properties, including anti-inflammatory effects, strong safety profiles and ease of manufacture. After all, there’s no point in finding a miracle microbe if it’s impossible to produce at scale,” said Bailey Cooper.
Through rigorous testing, the team at Ferryx uncovered a strain of Streptococcus thermophilus called FX856 that answered their research questions. “It survives – and even thrives – in an inflamed gut, shows anti-inflammatory activity, is safe and is straightforward to manufacture. It’s everything you’d want in a next-generation probiotic designed specifically for stressed or inflamed gut environments.”
What makes FX856 effective in reducing gastrointestinal inflammation?
Once the team identified strains that could survive and grow in response to iron, they started testing the strains’ effects on gut cells in vitro.
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“We focused on both gut epithelial cells and gut-associated leukocytes to understand how these bacteria interact with the gut environment. With FX856, we saw clear anti-inflammatory effects – specifically, reductions in key pro-inflammatory signals like NF-κB and IL-8,” said Bailey Cooper.
“We also assessed cell death and found that FX856 reduced epithelial cell death and helped reinforce the tight junctions between gut cells. Since stress can cause a ‘leaky gut’ by weakening these junctions, this ability to maintain barrier integrity is especially valuable,” she added.
Using a dextran sodium sulfate mouse model of colitis – a widely used, but extremely harsh model that chemically strips the gut lining – the team saw impressive results. “Mice treated with FX856 showed clinical improvements, including reduced weight loss and less gastrointestinal bleeding, which are two critical issues in human inflammatory bowel disease.”
In a human supplement trial using Ferrocalm, 78% of participants reported improvements in IBS symptoms. The team saw “improvements as early as two weeks in key IBS-related symptoms such as abdominal pain, cramping, bloating, loose stools, constipation and flatulence.”
“To see a probiotic show efficacy in a harsh preclinical model and then translate to meaningful symptom improvement in people was incredibly exciting.”
Future innovation is still needed to develop the field
Although gut microbiome research has boomed within recent years, it is still largely unchartered territory.
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“I often compare it [the gut microbiome] to outer space – we know there’s a lot out there, but we don’t fully understand how it all fits together, what each component does, or how it contributes to overall health. It’s complex, dynamic and still full of unknowns,” said Bailey Cooper.
“For instance, we know that dysbiosis and reduced microbial diversity are associated with poor gut health. But despite that, we still don’t have a reliable way to modify the microbiome with confidence that the intervention will work consistently across individuals.”
Importantly, Bailey Cooper and team are not attempting to “fix” the microbiome: “Instead, we’re introducing a new strain – FX856 – that has well-defined anti-inflammatory properties. But it’s not a colonizer. It’s a transient strain, meaning it passes through the gut, exerts its beneficial effects and is typically gone within a week after you stop taking it.”
The gut microbiome is incredibly individualized and there is still much to learn before attempting to reshape the microbiome.
“For now, our focus is on delivering targeted, reliable benefits in a way that works with that complexity, not against it.”
Despite seemingly being a way off fully understanding the gut microbiome, Bailey Cooper is hopeful for the future development of personalized probiotics.
“Imagine a future where someone with IBS could have their microbiome sequenced – we’d be able to identify key differences or imbalances. Then, based on that data, we could tailor an intervention – that kind of precision could lead to much better outcomes.”
“I think a truly personalized approach is where we’re headed – but we need a deeper understanding of how the microbiome works and how it's influenced by factors like stress, before we can get there,” she concluded.
