University of Houston Associate Professor Melissa Zastrow has received a $2.19 million National Institutes of Health grant to investigate how dietary metals such as zinc and iron alter the human gut microbiome and potentially trigger gastrointestinal disease.
The five-year funding from the National Institute of General Medical Sciences, awarded under grant number R35GM161898, backs ongoing efforts at the UH College of Natural Sciences and Mathematics to track trace minerals inside the human digestive tract. Traditional optical tools, such as green fluorescent proteins derived from jellyfish, require oxygen to function. Because the healthy human gastrointestinal tract is an anaerobic, low-oxygen environment, conventional sensors fail to operate effectively.
To bypass this limitation, Zastrow and her research team are engineering novel oxygen-independent biosensors. By introducing custom DNA into bacteria such as Lactobacillus—a genus of beneficial microbes commonly found in yogurt and probiotic supplements—the laboratory turns the microbes into living factories that produce fluorescent proteins. These proteins light up under a microscope when binding to specific trace metals, allowing real-time biochemical tracking.
“Metals impact the gut microbiota and correlate with various pathologies, but impacts are hard to predict and control because we do not understand all of their roles or how they are regulated between species and the host in the gut microbiota,” Zastrow stated.
Dietary metals are vital for human survival, but gut microbes also require them to function. When metal levels shift due to daily multivitamin use or nutritional deficiencies, the balance between beneficial bacteria and illness-causing pathogens can be disrupted. Despite this established connection, scientists have struggled to predict how dietary shifts alter microbial chemistry in the gut.
This fresh financial support enables the creation of a full sensor panel, expanding upon an initial 2020 NIH award that successfully demonstrated the capacity of these biosensors to detect copper and zinc. The laboratory is engineering sensors that emit across multiple wavelengths, ranging from green to near-infrared, while expanding detection to include manganese and iron with varying binding affinities.
Collaborating with partners at the Texas Medical Center, the UH team is investigating these dynamics within a realistic framework that avoids animal testing by employing 3D-printed flow-cell cartridges to circulate nutrients and mimic bacterial competition in the human small intestine, which is the primary site of dietary metal absorption.
“Right now, a lot of the evidence connecting metal changes to gut disease is just correlation, not necessarily causation,” Zastrow said. “Understanding how these bacterial communities handle changes in trace nutrients will eventually get us to the point of asking: Can somebody use this knowledge as a therapeutic approach to mitigate infection or chronic gut diseases?”
In Plain English: The Clinical Takeaway
- Tracking Minerals Without Oxygen: Researchers engineered glowing bacterial biosensors that work inside the oxygen-depleted human gut to monitor trace metals like iron and zinc in real time.
- Moving Past Correlation: By studying probiotic bacteria in 3D-printed small intestine models, scientists aim to prove whether metal fluctuations directly cause gastrointestinal diseases rather than merely coinciding with them.
- Targeted Therapies: The five-year NIH-funded project lays the groundwork for developing new treatments and refining how current dietary supplements and therapeutics are utilized to protect gut health.
Tracking Trace Metals Inside the Human Small Intestine
The human gastrointestinal tract presents significant obstacles for real-time molecular observation. The small intestine, where the body absorbs the vast majority of dietary metals, operates under strict anaerobic conditions. Standard optical monitoring techniques are rendered ineffective by the lack of oxygen.
By reprogramming natural light-sensing proteins, the Zastrow laboratory avoids the need for physical tabletop monitoring devices. The genetically modified bacteria assemble their own biosensors internally. When these proteins bind to target metals, their fluorescence intensity shifts, making it possible to measure biochemical concentrations directly under a fluorescent microscope.
The research focuses heavily on Lactobacillus species. Although these probiotic bacteria are known to be sensitive to metal fluctuations, their internal regulatory pathways remain largely unmapped. Observing how these populations compete for trace nutrients against other microbes provides foundational data on how dietary adjustments influence gut stability.
| Research Parameter | Methodology | Clinical Objective |
|---|---|---|
| Funding Source | NIH Award R35GM161898 ($2.19 Million) | Support a five-year investigation into gut microbiome metal regulation. |
| Biosensor Design | Oxygen-independent fluorescent bacterial proteins | Track real-time fluctuations of zinc, iron, copper, and manganese. |
| In Vitro Models | 3D-printed flow-cell cartridges (Texas Medical Center) | Simulate small intestine nutrient competition without animal testing. |
| Target Organisms | Lactobacillus and competitive gut microbiota | Differentiate correlation from causation in chronic inflammatory bowel conditions. |
Contraindications & When to Consult a Doctor
While the University of Houston study investigates how essential trace metals alter the human gut microbiome and trigger gastrointestinal disease, patients should not alter their intake of dietary supplements or probiotics based on preliminary research.
The grant work continues through the UH College of Natural Sciences and Mathematics, with future findings expected to guide the development of targeted microbial therapeutics.
References
- University of Houston. “UH Chemist Awarded $2.19M NIH Grant to Study How Gut Microbiomes Respond to Dietary Metals.” Press Release.
- National Institute of General Medical Sciences. NIH Award Number R35GM161898.
