How genes influence the microbes in our mouths

Illustration Credit: Agnieszka Grosso

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Scientists identified 11 specific regions of the human genome that significantly influence the composition and abundance of oral microbial communities, confirming that host genetics play a critical role in determining the mouth's bacterial environment.
• Methodology: Researchers analyzed whole-genome sequences derived from saliva samples of over 12,500 individuals, repurposing the data to simultaneously measure human genetic markers and the abundance of 439 common microbial species.
• Key Data: The study found that the FUT2 gene variant affected the levels of 58 oral bacterial species, while variations in the AMY1 gene influenced the abundance of more than 40 species.
• Significance: This research establishes a direct biological link between human genetics and oral health, suggesting that genetic factors can predispose individuals to cavities and tooth loss by altering the oral microbiome, independent of dental hygiene habits.
• Future Application: The statistical methods and findings developed in this study lay the groundwork for personalized dental care strategies and further large-scale investigations into how human genetics shape microbiomes throughout the body.
• Branch of Science: Genomics, Microbiology, and Oral Biology
• Additional Detail: Individuals with higher copy numbers of the AMY1 gene, which encodes a starch-digesting enzyme, showed increased populations of sugar-feeding bacteria and a statistically significant correlation with higher rates of denture use.

More Than Just Gut Cohabitants: How Gut Bacteria Control Immune Responses

The gut-brain axis is a bidirectional communication network linking the central nervous system with the enteric nervous system (the "second brain" in the gut) via neural, hormonal, and immune pathways.
Image Credit: Scientific Frontline / stock image

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Commensal gut bacteria utilize type III secretion systems, previously thought exclusive to pathogens, to inject effector proteins directly into human cells and actively manipulate host immune responses.
• Methodology: The research consortium constructed a large-scale interactome map identifying over 1,000 protein-protein interactions between bacterial effectors and human host proteins, validated by functional assays of immune signaling pathways.
• Key Data: Analysis revealed that genes encoding these secretion systems are significantly enriched in the microbiomes of patients with Crohn’s disease, with specific proteins targeting the NF-κB signaling pathway and cytokine responses.
• Significance: These findings fundamentally shift the understanding of the microbiome from correlation to causation, demonstrating that non-pathogenic bacteria are active agents capable of directly modulating human physiology and inflammation.
• Future Application: This mechanistic insight facilitates the development of targeted therapeutic strategies that modulate specific bacterial-host interactions to treat inflammatory bowel diseases and potentially other autoimmune disorders.
• Branch of Science: Microbiology, Immunology, and Network Biology
• Additional Detail: The study specifically highlights the modulation of Tumor Necrosis Factor (TNF) activity, a key cytokine in inflammation, providing a molecular basis for the efficacy of anti-TNF therapies in Crohn's disease.

Positive Interactions Dominate Among Marine Microbes, Six-Year Study Reveals

Lead study author Ewa Merz conducting maintenance on a pump below the Scripps Pier, which brings seawater to the surface for sampling.
Photo Credit: Riley Hale

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Marine microbial communities are driven primarily by positive, mutually beneficial interactions rather than competition, a trend that intensifies during periods of elevated ocean temperature.
• Methodology: Scientists utilized a six-year time series of high-frequency seawater sampling from Scripps Pier combined with DNA sequencing and computational analysis to map interactions among 162 abundant microbial taxa.
• Key Data: Analysis revealed that 78% of microbial associations were positive; specifically, warmer waters caused a 33% drop in total interactions but drove an 11% shift toward facilitation among the remaining connections.
• Significance: These findings challenge the traditional ecological emphasis on competition and predation, suggesting that cooperative networks are critical for microbiome stability and ecosystem function.
• Future Application: Integrating these positive interaction dynamics into climate models will enhance the accuracy of predictions regarding carbon cycling and food web stability in warming oceans.
• Branch of Science: Marine Microbial Ecology
• Additional Detail: The study identified specific "keystone" microbes that disproportionately influence community structure, noting that the identity of these critical species shifts in response to temperature changes.

Seawater microbes offer new, non-invasive way to detect coral disease

This brain coral shows the effects of stony coral tissue loss disease. The brown areas are healthy, the white areas are newly dead from the disease, and the light yellow areas are dead and colonized by endolithic algae.
Photo Credit: Amy Apprill ©WHOI

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Microorganisms in seawater immediately surrounding corals act as superior, non-invasive biomarkers for detecting diseases like Stony Coral Tissue Loss Disease (SCTLD) compared to microbes within the coral tissue.
• Methodology: Researchers performed a four-year longitudinal analysis (2020–2024) of brain coral (Colpophyllia natans) in the U.S. Virgin Islands, using genetic sequencing to compare microbial shifts in coral tissue versus adjacent seawater throughout a disease outbreak.
• Key Data: Microbial communities in seawater remained stable near healthy corals but shifted dramatically during disease infection, whereas internal coral tissue microbiomes varied inconsistently regardless of health status.
• Significance: This approach overcomes the limitations of traditional visual assessments by enabling non-destructive, presymptomatic detection of reef health declines, allowing for timely intervention.
• Future Application: Development of automated, rapid genetic monitoring systems to provide early warning signals for reef managers to mitigate disease spread.
• Branch of Science: Marine Microbiology and Coral Ecology.
• Additional Detail: The study, published in Cell Reports Sustainability, suggests seawater microbes respond to specific materials released by diseased corals, offering a clear signal even before visual lesions appear.

Hot spring bathing doesn't just keep snow monkeys warm

Video Credit: Abdullah Langgeng

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Hot spring bathing behaviors in Japanese macaques actively reshape the host "holobiont," specifically modifying lice distribution and gut microbiota composition beyond simple thermoregulation or stress relief.
• Methodology: Researchers conducted a comparative study over two winters at Jigokudani Snow Monkey Park, utilizing behavioral observations, ectoparasite monitoring, and gut microbiome sequencing to analyze differences between female macaques that bathed regularly and those that did not.
• Key Data: Bathers exhibited distinct lice distribution patterns (suggesting disruption of activity or egg placement) and a lower abundance of specific bacterial genera, yet showed no increase in intestinal parasite infection rates or intensity despite sharing communal water sources.
• Significance: The study provides empirical evidence that voluntary animal behaviors act as direct drivers of host-parasite and host-microbe interactions, challenging the assumption that shared water sources in the wild necessarily amplify disease transmission risks.
• Future Application: Insights from this research will aid in modeling the co-evolution of behavior and health in social animals and offer comparative frameworks for understanding how cultural practices, such as communal bathing, influence microbial exposure in primates.
• Branch of Science: Primatology, Ethology, and Microbial Ecology
• Additional Detail: The findings underscore the concept of the holobiont—an integrated system of the host and its symbiotic organisms—as a dynamic entity modulated by behavioral choices rather than solely by environmental constraints.

Honey Bees (Apis mellifera): The Metazoa Explorer

Photo Credit: Sarah Damen

Taxonomic Definition

Apis mellifera, commonly referred to as the Western honey bee, is a eusocial insect belonging to the family Apidae and the order Hymenoptera. Originally native to Europe, Africa, and Western Asia, the species has achieved a near-global distribution due to anthropogenic domestication for pollination services and honey production. It is the type species of the genus Apis and is distinguished by strict caste differentiation and perennial colony structures.

Koala (Phascolarctos cinereus): The Metazoa Explorer

Photo Credit: David Clode

Taxonomic Definition

The Koala (Phascolarctos cinereus) is an arboreal herbivorous marsupial native to Australia and the sole extant representative of the family Phascolarctidae. Taxonomically situated within the order Diprotodontia, it is most closely related to the Vombatidae (wombats). Its range extends along the eastern and southern distincts of Australia, spanning Queensland, New South Wales, Victoria, and South Australia, characterized by a dependence on sclerophyll forests dominated by the genus Eucalyptus.

Scientists develop molecules that may treat Crohn’s disease

Broad scientists designed molecules (pictured in teal) that can bind CARD9 (white with red and blue), a protein linked to inflammatory bowel disease.
Image Credit: Rush et al. Cell. DOI: 10.1016/j.cell.2025.12.013

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Researchers developed small-molecule drug candidates that mimic a rare, protective variant of the CARD9 gene to treat Crohn's disease and other inflammatory bowel diseases.
• Methodology: The team utilized a "binder-first" strategy, screening 20 billion molecules to identify binders to the CARD9 coiled-coil domain, followed by X-ray crystallography and competitive binding assays to isolate compounds that block inflammatory signaling.
• Key Data: The initial library screen evaluated over 20 billion compounds, ultimately yielding molecules that significantly reduced inflammation in both human immune cells and a mouse model expressing the human CARD9 gene.
• Significance: This work validates a complete "genetics-to-therapeutics" pipeline, proving that scaffolding proteins previously considered "undruggable" can be effectively targeted by mimicking naturally occurring protective variants.
• Future Application: Immediate efforts focus on optimizing these compounds for human clinical trials, while the broader methodology provides a blueprint for developing drugs against other difficult genetic targets.
• Branch of Science: Chemical Biology, Immunology, Genetics, and Molecular Biology.
• Additional Detail: The development strategy parallels the success of PCSK9 inhibitors for cholesterol, leveraging the safety profile of a natural genetic variant to guide drug design.

Oral bacteria play a role in chronic liver disease

The findings of the team led by Prof. Melanie Schirmer provide starting points for new therapies for advanced chronic liver disease.
Photo Credit: Astrid Eckert / TUM 

Scientific Frontline: "At a Glance" Summary

• Main Discovery: Specific oral bacteria were found to translocate to and colonize the gut in patients with chronic liver disease, where they actively contribute to disease progression rather than acting as passive bystanders.
• Mechanism of Action: These translocated bacteria express genes encoding collagen-degradation enzymes (collagenases) that damage the intestinal barrier, allowing bacterial pathogens to leak into the liver and exacerbate fibrosis.
• Methodology: The study combined comparative microbiome sequencing of patient samples with in vivo mouse experiments, demonstrating that introducing these specific oral strains into mice directly worsened gut barrier damage and liver condition.
• Key Observation: While healthy individuals maintain distinct oral and gut microbiomes, patients with advanced liver disease exhibited nearly identical bacterial strains in both sites, indicating significant bacterial migration.
• Diagnostic Application: The presence and abundance of the specific gene responsible for collagen degradation in stool samples were identified as a reliable biomarker for distinguishing patients with liver disease from healthy individuals.
• Therapeutic Potential: These findings suggest that therapies targeting the oral microbiome or inhibiting microbial collagenase activity could restore gut barrier integrity and slow the progression of chronic liver disease.

Plastic particles increase inflammation and cross barriers

Lukas Kenner, visiting professor, Department of Molecular Biology.
Photo Credit: Medizinische Universität Wien

Scientific Frontline: "At a Glance" Summary

• Core Discovery: Micro- and nanoplastics (MNPs) exacerbate chronic inflammatory bowel diseases (IBD) and penetrate biological barriers to accumulate in vital organs beyond the gastrointestinal tract.
• Methodology: Researchers utilized a mouse model of ulcerative colitis, orally administering polystyrene particles—a common plastic found in food packaging—to analyze molecular and histological interactions with the intestinal mucosa and immune system.
• Mechanism of Action: MNP exposure triggers pro-inflammatory activation of macrophages and induces gut dysbiosis, characterized by a decrease in beneficial bacterial species and an increase in potentially harmful, pro-inflammatory microbes.
• Data Point: Nanoplastic particles smaller than 0.0003 millimeters (0.3 micrometers) demonstrated the highest mobility, successfully traversing the intestinal barrier to deposit in the liver, kidneys, and bloodstream.
• Contextual Findings: The uptake of MNPs into the intestinal mucosa is significantly intensified during active inflammatory states, suggesting a feedback loop where existing inflammation facilitates further plastic accumulation.
• Primary Implication: MNPs are an underestimated environmental factor in the pathogenesis of chronic inflammatory diseases, highlighting an urgent need to evaluate the systemic health risks posed by the migration of the smallest particles into major organ systems.

What Causes Some People’s Gut Microbes to Produce High Alcohol Levels?

First author Cynthia Hsu examines a stool culture from a patient on an agar plate.
Photo Credit: UC San Diego Health Sciences

A study of people with a rare condition known as auto-brewery syndrome has found a link between gut microbes and symptoms of intoxication, pointing to new treatment strategies.

Researchers at University of California San Diego, Mass General Brigham, and their colleagues have identified specific gut bacteria and metabolic pathways that drive alcohol production in patients with auto-brewery syndrome (ABS). The rare and often misunderstood condition causes people to experience intoxication without drinking alcohol. The study was published in Nature Microbiology on January 8, 2026.

ABS occurs when gut microbes break down carbohydrates and convert them to ethanol (the alcohol found in intoxicating beverages), which then enters the bloodstream. While the metabolism of carbohydrates can produce small amounts of alcohol in everyone, levels can be high enough to cause intoxication in people with ABS. The condition is extremely rare but likely underdiagnosed due to a lack of awareness, diagnostic challenges, and stigma.

Researchers uncover molecular roots of fibrosis or tissue scarring in inflammatory bowel disease

Spatial mapping of intestinal tissue from patients with Crohn's disease or ulcerative colitis (shown here) allowed the researchers to characterize the cell types (shown as different colored dots) involved in fibrosis. In this image, inflammation-associated fibroblasts that deposit scar tissue roughly align with the cellular niche displayed in royal blue.
Image Credit: Courtesy of the Xavier lab

When inflammation in the body goes unchecked, it can cause fibrosis, or tissue scarring that may lead to organ dysfunction or even failure. This can happen in conditions such as inflammatory bowel diseases (ulcerative colitis and Crohn’s disease), chronic viral infections, interstitial lung fibrosis, chronic autoimmune skin diseases such as scleroderma, and scars associated with heart disease. Patients have few options for treating fibrosis, but new research points to a molecular pathway that could open the door to future treatment possibilities.

In earlier work, a team led by researchers at the Broad Institute and Mass General Brigham discovered a key cell type underlying fibrosis in inflammatory bowel disease (IBD). Now, in a new study in Nature, the team has characterized the crosstalk between this and other types of cells that leads to fibrosis. Their work also points to a molecule, GLIS3, that regulates this cell-to-cell communication and hadn’t been linked to IBD before. The findings suggest that interrupting this cellular pathway could one day help prevent or reduce fibrosis in patients with IBD or other diseases marked by chronic inflammation such as lung disease. 

Nutritional Science: In-Depth Description

Image Credit: Scientific Frontline / stock image

Nutritional Science is the multidisciplinary study of food and nutrients, investigating how the body ingests, digests, absorbs, transports, utilizes, and excretes these substances, and how they impact overall health, growth, and disease prevention.

Its primary goals are to define the physiological requirements for nutrients across the lifespan, understand the metabolic pathways involved in nutrient utilization, and determine the optimal dietary patterns to reduce the risk of chronic diseases and promote well-being.

Immune system keeps mucosal fungi in check

The yeast fungus Candida albicans (blue) breaks out of human immune cells (red) by forming long thread-like cells called hyphae. The part of the hypha that has already left the immune cells is colored yellow.
Image Credit: Erik Böhm, Leibniz-HKI

The yeast Candida albicans colonizes mucosal surfaces and is usually harmless. However, under certain conditions it can cause dangerous infections. A research team at the University of Zurich has now discovered how the immune system prevents the transformation from a harmless colonizer to a pathogenic mode. This happens, among other things, by sequestering zinc. 

The microbiome not only consists of bacteria, but also of fungi. Most of them support human and animal health. However, some fungi also have pathogenic potential. For instance, the yeast Candida albicans can grow in an uncontrolled manner on the oral mucosa, causing oral thrush. 

In severe cases by growing in a filamentous form, it can enter the bloodstream and cause systemic infections, which account for over one million deaths per year. This happens primarily in people with a weakened immune system on intensive care units, for instance individuals who are immunosuppressed because of a transplantation or cancer. 

New study reviews research linking probiotic and prebiotic supplements and skin health

Photo Credit: Christin Hume

Researchers from King’s College London and Yakult Science for Health have conducted a comprehensive review of existing research exploring how probiotic, prebiotic, and synbiotic supplements may influence skin health and disease.

The review mapped 516 studies from around the world examining the relationship between these supplements and various aspects of skin health, from general skin condition to the management of diseases such as atopic dermatitis, psoriasis, and acne. 

Our diet can influence skin health through its impact on the gut microbiome — the community of microorganisms living in our digestive tract. The concept of a gut–skin axis was first proposed nearly a century ago but has gained renewed attention in recent years, as growing evidence suggests that changes in gut microbes can affect skin condition and ageing. Probiotics, prebiotics, and synbiotics are thought to promote skin health by modifying the gut microbiome, which may in turn improve skin function and resilience. 

Why the "gut brain" plays a central role for allergies

This tissue section, taken from the intestine of a mouse unable to produce the neuropeptide VIP, clearly shows the striking frequency with which certain cell types occur on the intestine's surface. These include villous cells (red), mucus-producing goblet cells (yellow), Paneth cells (pink) and stem cells (green).
Image Credit: © Charité | Luisa Barleben

The intestinal nervous system, often referred to as the "gut brain", is essential in controlling digestion and maintaining the intestinal barrier. This protective layer, made up of the intestinal mucosa, immune cells and the microbiome, shields the body from the contents of the gut. Its effectiveness depends on the delicate balance among these components. If this balance is disrupted, inflammation, allergies, or chronic intestinal diseases can arise. The intestinal mucosa serves as the body’s primary defense against pathogens. While previous studies have shown that the intestinal nervous system is involved in immune responses in addition to digestion, its role in the development of intestinal epithelial cells has remained largely unclear until now. 

Stroke scientists gather more evidence for presence of ‘gut-brain axis’

Image Credit: Scientific Frontline / stock image

Research on mice by scientists at The University of Manchester has shed new light on why the guts’ immune system changes after a stroke and how it might contribute to gastro-intestinal problems. 

Published in Brain, Behavior and Immunity, the study adds to the emerging idea of the “gut-brain axis” – in which scientists suggest allows communication between the two organs in both health and disease. 

The study casts more light on the biology of stroke, a life-threatening medical emergency that disrupts blood flow to parts of the brain often causing long-term effects to mobility and cognition. 

Stroke patients are also at risk of secondary bacterial infections and often exhibit gastrointestinal symptoms including difficulty swallowing and constipation. 

Disrupting bacterial "chatter" to improve human health

Computer-rendered split image of bacteria on a tooth surface. When microbial communication is “on”, disease-associated species grow (left). Disrupting this communication (right) promotes health-associated bacteria.
Image Credit: University of Minnesota

Like all living things, bacteria adapt to survive. Over time, bacteria have been developing resistance to common antibiotics and disinfectants, which poses a growing problem for healthcare and sanitation. However, many species of bacteria are beneficial and even essential for human health. What if there was a way to change the behavior of bacteria in the body to prevent illness and poor health outcomes? 

Bacteria are very “talkative.” Constant streams of communication, known as quorum sensing, occur between and among the 700 species of bacteria that live in a human mouth. A number of them communicate via special molecules called N-acyl homoserine lactones (AHLs). 

A Microbial Blueprint for Climate-Smart Cows

Matthias Hess, with the UC Davis Department of Animal Science, and researchers at UC Berkeley, have identified which microbes in a cow's gut could help reduce methane. It brings them a step closer to engineering gut microbes to create more climate-friendly cows.
Photo Credit: Gregory Urquiaga / UC Davis

Each year, a single cow can belch about 200 pounds of methane. The powerful greenhouse gas is 27 times more potent at trapping heat in the atmosphere than carbon dioxide. For decades, scientists and farmers have tried to find ways to reduce methane without stunting the animal’s growth or productivity. 

Recent research at University of California, Davis, has shown that feeding cows red seaweed can dramatically cut the amount of methane that is produced and released into the environment. Until now, however, scientists did not fully understand how red seaweed changes the interactions among the thousands of microbes in the cow’s gut, or rumen. 

What Is: Hormones

The "Chemical Messenger"
The Endocrine System and Chemical Communication
Image Credit: Scientific Frontline

The Silent Orchestrators

Hormones are the silent orchestrators of the human body. They are the unseen chemical messengers that, in infinitesimally small quantities, conduct the complex symphony of life. These powerful molecules control and regulate nearly every critical function, from our mood, sleep, and metabolism to our growth, energy levels, and reproductive functions.

At its most fundamental level, a hormone is a chemical substance produced by a gland, organ, or specialized tissue in one part of the body. It is then released—typically into the bloodstream—to travel to other parts of the body, where it acts on specific "target cells" to coordinate function.

The power of this system, which has identified over 50 distinct hormones in humans, lies in its exquisite specificity. Although hormones circulate throughout the entire body, reaching every cell, they only affect the cells that are equipped to listen. This is governed by the "lock and key" principle: target cells possess specific "receptors," either on their surface or inside the cell, that are shaped to bind only to a compatible hormone. This report will delve into the world of these powerful molecules, exploring the intricate system that creates them, the chemical language they speak, and the profound, lifelong impact they have on our daily health and well-being.