Detoxifying methylmercury using a gut microbe

An engineered human gut microbe can detoxify methylmercury consumed by pregnant mice and reduce its harmful neurological effects in their fetuses and offspring, according to researchers supported in part by NIEHS.

The neurotoxic form of mercury is methylmercury, which can accumulate to high levels in seafood and pose significant health risks for pregnant women. Currently available treatments are not highly effective, especially if not given right after exposure, and they can have adverse effects.

The researchers examined whether an engineered gut microbe could detoxify methylmercury consumed by mice. They obtained gene sequences from a mercury-resistant bacterial strain isolated from polluted mines and integrated the sequences into the genome of the human gut bacterium Bacteroides thetaiotaomicron. The engineered gut microbe demethylated methylmercury in cells and in the intestines of mice that consumed the toxic metal.

In addition, the microbe reduced methylmercury accumulation in the liver, brain, and placenta of pregnant mice, and in the fetal brain, where cellular stress genes became less active, resulting in a reduction of adverse neurological reactions in developing offspring. According to the authors, the engineered gut microbe could curtail the accumulation and harmful effects associated with methylmercury exposure. (JW)

Citation: Yu KB, Chandra F, Coley-O'Rourke EJ, Paulson ET, Novoselov A, Zhang D, Finnigan D, Paramo J, Lopez-Romero A, Dong TS, Schartup AT, Hsiao EY. 2025. An engineered gut bacterium protects against dietary methylmercury exposure in pregnant mice. Cell Host Microbe 33(5):621-31.e7.

Harnessing microbes for remediation

A robust gel matrix that encapsulates bacterial biofilms could prolong the ability of the microbes to withstand environmental changes and effectively remediate soils contaminated with polychlorinated biphenyls (PCBs), according to NIEHS-funded researchers.

Exposure to PCBs from sediments can be harmful to human health. PCBs can be degraded by biofilms of the bacterium Paraburkholderia xenovorans LB400, but the biofilms themselves can degrade over time due to harsh environmental conditions. To potentially solve this problem, the researchers explored the effects of encapsulating biofilms with Sol-Gel, which is a strong, stable, and highly porous matrix that provides a framework to protect biofilms from environmental damage.

By tuning their previous chemical recipe, the researchers developed a new Sol-Gel product to enhance the longevity of biofilms formed on corn kernel biochar surfaces. This novel encapsulation approach protected biofilms against adverse environmental changes, such as high salinity and continuous shear force. It also extended cell viability for more than three months without additional carbon sources. According to the authors, the method could protect biofilms used for the remediation of contaminated sediments, offering benefits to ecosystems and public health. (JW)

Citation: Dong Q, Mattes TE, LeFevre GH. 2025. Development of a novel PCB-degrading biofilm enriched biochar encapsulated with Sol-Gel: a protective layer to sustain biodegradation activity. ACS ES T Eng 5(4):883-98.

Understanding the longer term effects of ozone exposure

Early-life ozone exposure is linked to worse respiratory health in childhood, according to new research funded in part by NIEHS.

Short-term ozone exposure has been associated with adverse respiratory health outcomes such as asthma, which affects the airways in the lungs, causing breathing difficulties. But research linking postnatal ozone exposure to childhood asthma and wheeze — a high-pitched whistling sound that occurs during breathing — has yielded differing results and has neglected evaluations of mixtures of air pollutants.

In the new study, the researchers analyzed data from 1,188 participants in six U.S. cities with relatively low ozone concentrations. The results showed that exposure to higher levels of ozone in the first two years of life was linked to a higher risk of asthma and wheeze at age 4 to 6 years but not at age 8 to 9 years. In addition, higher exposure to ozone in mixtures with fine particulate matter and nitrogen dioxide was associated with asthma and wheeze in early childhood.

According to the authors, it is important to study the effects of postnatal ozone on the development of respiratory conditions because it represents the most commonly exceeded air pollutant standard among children in the U.S. (JW)

Citation: Dearborn LC, Hazlehurst MF, Sherris AR, Szpiro AA, Day DB, Loftus CT, Blanco MN, Adgent MA, Andrade-Torres AR, Ni Y, Crocker ME, Bi J, Kaufman JD, Nguyen RHN, LeWinn KZ, Moore PE, Carroll KN, Karr CJ. 2025. Early-life ozone exposure and asthma and wheeze in children. JAMA Netw Open 8(4):e254121.

Peptides from ocean microbes can predict harmful algal blooms

Recent research funded in part by NIEHS shows that changes in the levels of peptides from bacteria in the ocean can predict a harmful algal bloom (HAB). The rise in peptide levels occurs at least 24 hours before an HAB.

Blooms can be hazardous to human and aquatic life because the algae produce substances that are toxic to nervous systems. Current monitoring techniques, such as satellite imaging, rely on the blooms to reach a certain mass for detection, but at that point the toxins may already have contaminated drinking water and seafood.

The researchers sought to determine whether proteins produced by bacteria in response to the changing conditions in the ecosystem before an HAB may serve as an early warning sign, or biomarker. They took ocean water samples every four hours for 22 days, capturing one full HAB cycle and an additional pre-bloom phase of a second HAB. After quantifying thousands of peptides produced by the ocean microbiome, they found that the significant changes in the abundance of 12 peptides were detectable, reliable, and rapid indicators that preceded an HAB at least 24 hours in advance.

According to the authors, the peptide biomarkers they identified underwent a detectable and significant shift before bloom development that may provide a window of opportunity to alert reporting agencies of bloom development before public exposure and safety issues. The next phase of the project involves looking at the dissolved metabolites, or small molecules, in the water at the critical time frames identified. This will allow researchers to determine if there are unique chemical signals that could inform us as to why HABs start. The work was led by Miranda Mudge, Ph.D., who was funded through the NIH F31 fellowship training program. (DK)

Citation: Mudge MC, Riffle M, Chebli G, Plubell DL, Rynearson TA, Noble WS, Timmins-Schiffman E, Kubanek J, Nunn BL. 2025. Harmful algal blooms are preceded by a predictable and quantifiable shift in the oceanic microbiome. Nat Commun 16(1):3986.