Detailed ‘movies’ that show how electrical charge flows through a layered material known as a 2D perovskite provide insights into how the perovskite could be fine-tuned to develop electronic devices that operate faster, last longer, and perform more efficiently[1].
“Researchers can use these results to carefully select the right number of layers and tailor surface chemistry to design improved 2D perovskite materials for applications such as solar cells and photodetectors,” says Lijie Wang from KAUST, part of the team behind the work.
Perovskites can form thin crystalline films that convert light into electricity or vice versa. They are being commercialized in next-generation solar panels and show promise in applications such as light-emitting diodes (LEDs). Researchers make perovskites by combining inorganic materials like lead iodide with carbon-based organic molecules. However, exposure to heat, moisture, or intense light can degrade perovskites and their performance.
Researchers hope to solve these problems using closely related materials called 2D perovskites, in which the organic and inorganic components are arranged in alternating flat sheets, rather like a sandwich. The organic molecules serve as a barrier, preventing moisture and oxygen from reaching the inorganic slabs between them. “This structure significantly slows down the degradation processes and improves thermal stability,” says KAUST’s Omar Mohammed, who led the team.
In devices such as solar cells and LEDs, electrical charge is carried by negative electrons and the positive ‘holes’ they leave behind. The insulating organic components in 2D perovskites confine these charges to the inorganic slabs. While this can improve the efficiency of LEDs, it hinders the movement of charge in solar cells and photodetectors.
The KAUST team has now studied how the structure of 2D perovskites affects the behavior of electrons and holes using four-dimensional scanning ultrafast electron microscopy (4D-SUEM).
First, a laser pulse excites the perovskite, generating mobile electrons and holes that quickly spread out. An instant later, the microscope fires a pulse of electrons that bounce off the material and into a detector. Crucially, these pulse electrons are more readily reflected by parts of the sample with higher electron and hole densities.
By taking repeated snapshots of the perovskite in this way, the system creates a movie showing how the distribution of electrons and holes on the surface changes over mere quadrillionths of a second.
The team used this approach to study 2D perovskites with inorganic slabs, either one, two, or three layers thick. In samples with two or three layers, electrons and holes separated more easily, and the charges were more likely to move rapidly across the surface rather than through the bulk of the material. “Faster surface diffusion allows for more efficient charge collection in devices such as solar cells and photodetectors, leading to improved device performance,” explains Wang.
“The next stage of our research is to investigate how charge carriers behave under real-world conditions, such as high temperatures, intense illumination, or radiation — all conditions that devices might encounter in harsh environments,” adds Mohammed.
Gall crabs are tiny and yet these crustaceans have evolved fluorescence to help them be concealed within hideouts they have created in the coral itself[1].
“These crabs are everywhere,” says Susanne Bähr, who led the study. “People ask how they can see them, and I say, ‘Take a mask and a snorkel and go anywhere you find coral, and you’ll see them.’”
Gall crabs don’t just live among the corals; they have a strong symbiotic relationship with them. Some invertebrates hide within the branches and crannies of corals, but for gall crabs, the connection goes much deeper.
“They settle on a coral as larvae, and then, somehow, they make the coral grow around them in very specific shapes. We don’t know how they do that,” says Bähr. Female crabs then stay in this den for the rest of their life, feeding on nutritious mucus and producing larvae, while the males rove about looking for females to mate with.
Bähr noticed that gall crabs fluoresce when on a night dive. “I had been working with these crabs for some time, so this observation was particularly intriguing, and I started reading about fluorescence. It’s been well studied in reef fish, where it has a broad array of functions. However, less is known about fluorescence in crustaceans, and yet crabs and shrimps are enormously diverse. So I wondered if we could find similar patterns in crustaceans as we’ve observed in fish.”
Bähr and colleagues collected 286 gall crabs from 14 different genera, sampling from all the known host coral genera in the Red Sea and Indian Ocean. They developed an imaging technique to identify exactly which parts of the different crabs fluoresced, as well as how much of each body part was fluorescent. Using this, they carried out a morphological analysis of the different species. They also built an evolutionary tree based on the crabs’ genomic sequencing data.
The morphological analysis showed that the fluorescence patterns on the crabs grouped into four clusters. One cluster included non-fluorescent crabs, and another included crabs with diverse fluorescent patterns; the final two had strong fluorescence on specific body parts. The evolutionary tree identified the genus in which fluorescence first appeared – probably covering most of the body – and showed that for some specific lineages, fluorescence has been lost or reduced.
The researchers suggest that fluorescence evolved in different types of gall crabs to help camouflage them in their coral dens. Different gall crab species live in dwellings of different shapes on the coral — for example, open tunnels or enclosed galls — and the fluorescence patterns affect their visibility in their dens.
Bähr offers the examples of a species that lives in cylindrical pits in the coral. “Basically, the back of the crab is sticking out a little bit. It has this really striking fluorescence pattern that disrupts how the crab looks. It disguises the outline of the crab, so you really can’t see a crab shape.”
Francesca Benzoni, Bähr’s supervisor at KAUST, highlights the importance of better understanding coral reef ecosystems. “Gall crabs are one of the many types of invertebrates living in association with corals on tropical reefs,” she says. “Much remains to be discovered on cryptic and poorly studied reef invertebrates and their fundamental biology, ecological role, and the role they play in the resilience of coral reef ecosystems in the Red Sea and worldwide.”
Understanding these broader systems is also important to Bähr. “I want to use my research to highlight the importance of these coral-associated invertebrates and their significance for coral reef ecosystems,” she says. “They’re generally overlooked, and it’s very important for us to understand how many there are, why they’re there, and what they do for reef persistence and resilience.”
To tackle the growing ecological threat of microplastics, magnetic nanoparticles have been created that can remove plastic fragments from water. Researchers used machine learning to identify the ideal removal conditions for particular microplastics, a strategy that may help to optimize other clean-up methods[1].
Microplastics are scraps of waste plastic, typically 1 micrometer to 1 millimeter in size, which are now ubiquitous in the environment. The particles adsorb toxic metals and organic pollutants. They are easily ingested by aquatic life, and once microplastics and their toxic payloads are in the food chain, they can accumulate in other species, including humans.
Methods to remove microplastics from wastewater face various drawbacks. Using light to destroy microplastics is effective but expensive and energy-intensive. Certain microbes can break down microplastics, but this generates other molecules that may themselves be toxic.
Magnetic nanoparticles offer a simple, low-cost and environmentally friendly solution. But these nanoparticles are prone to oxidation and may clump together in water, reducing their effectiveness, explains Rifan Hardian of KAUST’s Physical Science and Engineering Division.
A collaboration between KAUST and University Malaysia Terengganu has now developed magnetic nanoparticles that overcome these problems and remove not only microplastics but also the organic pollutants they carry.
First, the researchers prepared iron oxide nanoparticles with a protective porous silica coating. Then, they added linker molecules to the silica, which allowed them to decorate the particles with more molecules called imines. This covered the nanoparticle with molecular strands that capture microplastics, while chemical groups in the imines bind organic pollutants.
The researchers tested these nanoparticles on different sizes of polystyrene microplastics carrying common pollutants. They used a magnet to pull the nanoparticles from the water, along with their microplastic cargo and then washed off the fragments so the nanoparticles could be reused.
But with so many different variables to consider — from the number and size of microplastics in the water, to the concentration of imines on the magnetic nanoparticles — the researchers needed an efficient way to identify which factors offered the best clean-up solution.
So they used a method called ‘design of experiments’ to determine which combinations of variables would produce the most useful data and then fed those data into a machine-learning system that quickly identified any trends. This highlighted ways to maximize microplastic removal while minimizing the amount of imine required.
For example, a relatively low concentration of imines could remove 90 percent of a sample of microplastics roughly 300 micrometers in size. With fewer, smaller microplastics, an extremely low concentration of imines could still achieve about 80 percent removal efficiency.
“With our machine-learning model, we can predict the efficiency of the microplastic removal at various numbers and sizes,” says Hardian. “This prediction can then be used to determine the required adsorbent concentration.”
“The next milestone will be applying our methodology in other microplastic removal technologies so we can compare the efficiency of available technologies,” says Gyorgy Szekely, who led the KAUST researchers. They also hope to develop an autonomous laboratory system that could continuously optimize the experimental conditions.
In August 2023, an intense marine heatwave along the Saudi Arabian coast of the central Red Sea coincided with the mass beaching of dead fish, prompting a team of KAUST researchers to investigate[1].
Temperatures in oceans and seas around the globe are rising due to anthropogenic climate change, increasing stress on marine ecosystems and wildlife. Marine heatwaves occur when localized water temperatures exceed historical average sea temperatures; extreme events occur when temperatures reach 2ºC or more above average for a prolonged period. This can have multifaceted and catastrophic effects on marine life.
“Coastguard officials began reporting high numbers of dead fish and invertebrates, such as cuttlefish, washing ashore,” says Matthew Tietbohl, postdoctoral fellow, who led the project under the supervision of KAUST’s Maggie Johnson. “By the time we got to the beaches, about a week later, the fishes had degraded enough that we couldn’t collect useful samples to determine the cause of death, such as possible bacterial infection.”
The team found almost 1,000 fish washed ashore along a 60-kilometer stretch of coastline north of Thuwal. The mortality event included at least 54 species of fish, highlighting a broad impact across the reef community. This is a highly conservative estimate, notes Tietbohl: It was impossible to survey the entire 60+ kilometers of impacted coastline, and only a quarter of dead fish typically wash ashore.
In collaboration with Ibrahim Hoteit’s team, the marine scientists turned to satellite data analyses to understand the environmental conditions in the weeks prior to the mass beaching.
Satellite data of sea surface temperatures confirmed that an intense marine heatwave was spread across the whole region. However, the area just north of where the fish were found had the highest water temperatures and the strongest daily temperature changes, which the researchers believe had placed physiological stress on the fish. The weakened and dying fish were likely pushed southwards by prevailing winds and currents.
“Just like humans, all creatures struggle when they get too hot: Once a certain thermal threshold is reached, it becomes very difficult for their bodies to function correctly,” explains Tietbohl. “Bodies also burn more energy when stressed and require more oxygen, but higher temperatures reduce the amount of oxygen that water can hold.”
Extreme heat can also lead to stratification, where water settles into layers with limited mixing. This reduces oxygen exchange and stops the water from cooling down. Suffocating algal blooms are common in this scenario, although the researchers did not find evidence of this phenomenon during the 2023 heatwave. Extensive coral bleaching also occurred in the region that summer, which is also an indication that temperatures were high.
“Satellite instruments tend to underestimate water temperatures in the Red Sea, so it is likely the region experienced temperatures well above 2ºC of warming,” adds Tietbohl.
“These results, together with data from similar fish kills in summer 2024, suggest that the Red Sea maximum temperatures may be getting too hot for coral reefs and many marine creatures,” says Johnson. “Their chances of recovery would be improved by implementing fishery regulations that limit fishing during this stressful time.”
“We’ve presented our findings to the Saudi National Center for Wildlife and are in discussions to incorporate mass fish mortality monitoring into their wider marine animal stranding network,” says Tietbohl. “Improved monitoring would feed back into temperature models to help predict marine heatwaves, thus boosting preparation windows and supporting possible mitigation strategies or damage control.”
The holy month of Ramadan is a sacred time when millions of Muslims around the world embark on a profound spiritual journey of fasting, prayer, and reflection. But it is also a time when many face serious health risks, as going without food or water from sunrise to sunset — often in scorching heat — can lead to dangerous levels of dehydration.
Now, scientists at KAUST have found a surprisingly simple way to track the body’s water levels during fasting: by measuring how skin interacts with a touchscreen[1].
It is not only useful when fasting. The research team, led by electrical engineer Tareq Al-Naffouri and colleagues at KAUST, showed that the same method applies to athletes, who often experience dehydration due to intense exertion and fluid loss through sweat.
“It is also reasonable to expect that the approach could one day benefit other vulnerable groups, including the very old, the very young, and those with kidney disease,” says Al-Naffouri.
To demonstrate the concept, Al-Naffouri’s team used a basic capacitive sensor — the same type found in smartphone screens — capable of detecting subtle shifts in skin moisture. When a fingertip touches the sensor, it registers changes in skin capacitance, a measure of how well the skin stores electric charge, which varies with hydration levels.
The researchers suggest that this data could eventually allow people to monitor their hydration in real time — no needles, wearables, or lab work required. A quick touch could alert someone to drink water or replenish fluids before symptoms like dizziness or fatigue begin to set in.
“We envision real-time, everyday, user-friendly hydration monitoring, where users simply place their finger on their smartphone screen to assess their hydration status,” says study author Soumia Siyoucef, a former visiting student in Al-Naffouri’s research group.
To validate their technology, the KAUST team collected more than 4,000 fingertip readings from people either observing Ramadan and fasting much of the day or athletes engaged in a game of ultimate Frisbee or working out at the gym. They trained machine-learning models to convert small changes in skin conductance into a measure of the body’s water content.
When put to the test, the system delivered impressive results — accurately distinguishing between hydrated and dehydrated states up to 92 percent of the time among athletes and 87 percent among fasting individuals.
Coral reefs form a vital part of the marine ecosystem, playing host to diverse species and supporting multiple industries, including fisheries, tourism, and recreation. However, these fragile ecosystems are under increasing threat from climate change, with warming oceans increasing stress on the coral animals and their symbiotic algal partners.
A new remote sensing tool developed by KAUST researchers has created an effective and efficient method of monitoring and predicting both the scope and severity of coral bleaching in the Red Sea[1]. The tool – developed by KAUST in partnership with SHAMS, General Organization for the Conservation of Coral Reefs and Turtles in the Red Sea – could aid conservation management and policymaking by enabling targeted, integrated management strategies to prioritize specific areas for intervention. It is applicable in the Red Sea as well as across the world.
The algae living within corals share nutrients and resources, giving corals their distinctive color. When corals are under stress and competing for limited resources, they ‘kick out’ their algal partners that help with nutrition. This results in bleaching, where corals lose their pigmentation and gradually turn white. This process weakens the coral animal and leaves it more vulnerable: prolonged bleaching events can kill corals and decimate reefs.
“Monitoring the health of coral reefs amid climate change is crucial, and satellite remote sensing provides a cost-effective strategy that is more efficient than traditional field sampling, which can be time-consuming and resource-intensive,” says Elamurugu Rajadurai Pandian at KAUST, who worked on the project during his Ph.D., under the supervision of KAUST’s, Ibrahim Hoteit.
The new tool utilizes the extensive datasets collected by satellite imaging every five days. While previous studies have used satellite imaging to monitor coral bleaching events, the team took this technique a step further by including an analysis of the severity of bleaching. This means that areas can be rapidly graded according to how intense the bleaching is likely to become.
“Healthy and bleached corals reflect light differently, and satellites can detect these variations,” says Rajadurai Pandian. The researchers took advantage of these differences in color and brightness in thousands of satellite images to accurately identify bleached corals.
Firstly, they analyzed how much light was reflected from the ocean floor by both healthy and bleached corals. Then, they used a mathematical technique called the least-squares approach. This helped identify patterns in the data and accurately segregated bleached corals from healthy ones, making the overall detection rate more precise and reliable.
“The detection accuracy depends on the atmospheric correction of satellite imagery, which is complicated by the Red Sea’s proximity to deserts and frequent dust storms,” says Rajadurai Pandian. “We used an advanced algorithm that removed erroneous reflectance values caused by aerosols and particulates. This significantly improved the accuracy of satellite ocean color data retrievals in our model, particularly over the complex, reef-filled shallow waters of the Red Sea.”
Their model also has improved spatial resolution compared to previous models, providing detailed analyses of coral health every ten meters. By monitoring bleaching severity, ranging from low to high, scientists can gain deeper insights into coral resilience and recovery potential.
“By serving as an early warning system for coral bleaching, our method will enable faster responses and better conservation strategies,” concludes Hoteit. “Such high-resolution monitoring will support sustainable fisheries and tourism management while also contributing to climate change research by tracking environmental changes in marine ecosystems.”
Combining data across mismatched maps is a key challenge in global health and environmental research. A powerful modeling approach has been developed to enable faster and more accurate integration of spatially misaligned datasets, including air pollution prediction and disease mapping[1].
Datasets describing important socio-environmental factors, such as disease prevalence and pollution, are collected on a variety of spatial scales. These range from point data values for specific locations up to areal or lattice data, where values are aggregated over regions as large as countries.
Merging these geographically inconsistent datasets is a surprisingly difficult technical challenge, embraced by biostatistician Paula Moraga and her Ph.D. student Hanan Alahmadi at KAUST.
“Our group develops innovative methods for analyzing the geographical and temporal patterns of diseases, quantifying risk factors, and enabling the early detection of disease outbreaks,” says Moraga. “We need to combine spatial data that are available at different resolutions, such as pollutant concentrations measured at monitoring stations and by satellites, and health data reported at different administrative boundary levels.”
Alahmadi and Moraga developed their new model through a Bayesian approach, which is often used to integrate large spatial datasets. Bayesian inference is usually performed using Markov chain Monte Carlo (MCMC) algorithms, which explore datasets through a ‘random walk’. The algorithms decide on each next step based on the previous one until they get as close as possible to a target (or ‘posterior’) distribution. However, MCMC can take up a lot of computational time, so the researchers used a different framework called the Integrated Nested Laplace Approximation (INLA).
“Unlike MCMC, which relies on sampling, INLA uses deterministic approximations to estimate posterior distributions efficiently,” explains Alahmadi. “This makes INLA significantly faster while still providing accurate results.”
The researchers demonstrated the power of their model by integrating point and areal data in three case studies: the prevalence of malaria in Madagascar, air pollution in the United Kingdom, and lung cancer risk in Alabama, USA. In all three, the model improved the speed and accuracy of predictions while providing insight into the importance of different spatial scales.
“In general, our model gives more weight to point data because they offer higher spatial precision and are often more reliable for detailed predictions,” says Alahmadi. “In all studies, point data played a dominant role. However, the influence of areal data was greater in the air pollution study. This is primarily because the air pollution areal data had a finer resolution, which made them more informative and complementary to the point data.”
Overall, the project addresses the increasing need for data analysis tools that support evidence-based decisions in health and environmental policy. For example, if public health officials can quickly assess disease prevalence, then they can work more effectively to allocate resources and intervene in high-risk areas.
The new model could be adapted to capture dynamic changes over space and time and to address biases that may arise due to preferential sampling in certain areas. The researchers plan several other applications of their model, such as using satellite pollution data to estimate disease risks.
“We hope to combine satellite and ground-based temperature data to detect thermal extremes in Mecca, particularly during the Hajj season, where heat stress is a serious public health concern,” says Moraga. “We also intend to monitor air pollutants and track emissions, supporting Saudi Arabia’s journey toward its net-zero goals.”
An electrochemical sensor designed to address a global health issue that particularly impacts people in the Middle East and North Africa (MENA) has been created by a multidisciplinary team at KAUST. The sensor detects low vitamin D levels in blood samples, providing early warning of an essential vitamin deficiency that can have severe health consequences if left untreated[1].
“Vitamin D deficiency can result in broad health complications including cardiovascular disease, autoimmune disorders, neurodegenerative diseases and skeletal deformities,” says Sharat Chandra Barman, a postdoc in the labs of Husam Alshareef and Dana Alsulaiman, the project’s co-leaders. “Early diagnosis of vitamin D deficiency is crucial.”
The body makes vitamin D in the skin when exposed to sunlight, but in hot regions of the world people often minimize their sun exposure.
“Despite ample sunshine in Saudi Arabia and the MENA region, the prevalence of vitamin D deficiency is alarmingly high, making it a critical and often overlooked public health challenge,” Alsulaiman says. Around 80 percent of the region’s population is deficient in vitamin D, and 16 percent of people in Saudi Arabia are severely deficient.
It is difficult to measure the essential vitamin at clinically relevant concentrations in a blood sample.
“The molecule’s small size, low circulating concentrations in the blood, and its structural similarity to other biomolecules all present challenges,” Alsulaiman says. As a result, vitamin D testing is typically carried out on specialized equipment only available in large urban centers.
To create a simple yet accurate vitamin D testing device for use even in remote healthcare centers, the team created a novel electrochemical sensor that combined MXene 2D nanomaterials and vitamin D selective antibodies.
“MXenes have several features that suit biosensor applications,” Barman explains. “They are biocompatible, possess excellent electrical conductivity, and their surface is covered with tunable chemical groups that can enable further device functionality to be incorporated.”
The team used these chemical groups to attach vitamin D-binding antibodies to the MXene surface.
“Combining MXenes with antibodies resulted in a very sensitive and highly selective material for point-of-care vitamin D detection,” Barman says. The team was able to show that when the antibodies on the device bound to vitamin D, the current flow through the biosensor fell measurably, with the size of the electrical response proportional to the concentration of vitamin D in the sample.
The sensor had a vitamin D detection limit of just 1 picogram per milliliter of sample, with a dynamic range of 0.1–500 nanograms per milliliter. “This range effectively covers clinically relevant vitamin D levels, from deficiency to insufficiency, sufficiency, and toxicity ranges,” Barman says.
“The sensor also demonstrated high selectivity, showing minimal interference from non-target biomolecules like glucose, vitamin C, and vitamin B12,” he adds.
“Our synergistic combination of MXenes and antibodies enabled us to develop a biosensing platform for vitamin D deficiency that is low-cost, rapid, and decentralized – this advances accessible healthcare solutions in line with the goals of Saudi’s visionary Health Sector Transformation Program,” Alsulaiman says.
Hydrogen is a clean-burning fuel that could help to replace fossil fuels in transportation, the chemicals industry, and many other sectors. However, hydrogen is also an explosive gas, so it is essential to have safety systems that can reliably detect leaks in a variety of circumstances.
KAUST researchers have invented a robust, highly sensitive, low-cost hydrogen sensor that outperforms commercial detectors, offering a vital safeguard for the burgeoning hydrogen economy[1].
“Conventional hydrogen sensors face several limitations,” explains Suman Mandal of the Physical Science and Engineering Division at KAUST, a member of the team behind the work. “These sensors often respond slowly to hydrogen leaks, cannot detect trace levels of hydrogen, and must be heated during operation, for example.”
The researchers have overcome these problems using a semiconducting polymer called DPP-DTT, which they coated onto a pair of platinum electrodes. Exposure to hydrogen reduced the current flowing through the device by up to 10,000 times, offering a powerful detection signal, with the drop in current corresponding to the concentration of hydrogen.
“This high responsivity ensures rapid and precise detection of gas leaks, which is essential for safety in industrial and transportation sectors,” says Mandal
The device operates at room temperature and can detect traces of hydrogen at just 192 parts per billion. It responds within one second of exposure and consumes barely two microwatts of power. Laboratory tests showed the device could operate over a wide temperature and humidity range and remained functional for two years.
The researchers tested the device in various real-world scenarios, which included hydrogen leaking from a pipe and bursting hydrogen-filled balloons in a room. They even mounted the device on a drone and flew it through an area where a hydrogen leak had occurred. In all scenarios, the device performed better than commercial sensors.
The sensor could also detect hydrogen in mixtures of volatile molecules such as ethanol and acetone, and in complex gas mixtures. The sensor only failed when the atmosphere lacked any oxygen, which provided an important clue about how it works.
Oxygen from the air enters the polymer and draws electrons from the material. This increases the current flowing through the device and leaves oxygen within the polymer and on the electrodes. If there is any hydrogen in the surrounding air, it also passes through the polymer and reaches the electrodes, where it splits into hydrogen atoms that stick to the platinum’s surface. Hydrogen and oxygen atoms then combine to form water, which escapes the device. Removing this oxygen reduces the current flowing through the device, which signals the presence of hydrogen.
“This is an entirely new hydrogen sensing mechanism,” Mandal says.
Using an inexpensive screen-printing method, the sensor could be manufactured at a low cost, making it an affordable and practical way to rapidly identify hydrogen leaks.
The team has filed a patent on the work, and plans to collaborate with a company to further develop the technology. “I believe these efforts will help address hydrogen safety issues in a cost-effective and environmentally friendly manner,” says Mandal.
The need to tackle antibiotic resistance is becoming more urgent, posing threats to the health of all species, as antibiotic resistance genes (ARGs) proliferate in the wider environment. Wastewater treatment plants are a key hotspot for the spread of antimicrobial resistance, because ARGs present in waste from humans can pass through the treatment process intact and disseminate into the environment.
“Solid waste, or sludge, is a byproduct of wastewater management that is regularly discharged into the environment after wastewater is treated,” says Julie Sanchez Medina, Ph.D. student at KAUST, who is supervised by faculty member Pei-Ying Hong. “However, sludge now contains considerable numbers of ARGs, and they are free to potentially move between species in the sludge, spreading antimicrobial resistance still further.”
Now, a metagenomics study by Sanchez Medina and co-workers has demonstrated that one type of bioreactor used in some wastewater plants – anaerobic membrane bioreactors – may be better at reducing the amount of ARGs released into the environment[1].
Membrane bioreactors use a bacterial digestion process to break down organic pollutants in wastewater. This digestion process either uses aerobic bacteria (those that thrive with oxygen) or anaerobic bacteria (without oxygen). The wastewater is then filtered through a membrane to separate out the contaminants, resulting in clean fluid effluent and leaving behind the solid sludge.
“We wanted to examine whether there are differences in the amount of ARGs and antibiotic-resistant bacterial strains in the sludge produced by aerobic or anaerobic membrane bioreactors,” says Sanchez Medina.
The team compared two systems that were treating the same stream of wastewater, and collected sludge from each of them in two independent runs during a five-month period. They extracted DNA from the sludge, then sequenced and analyzed it with bioinformatic tools. The resulting datasets enabled the researchers to estimate the abundance of ARGs according to the sludge volume that was released by each bioreactor.
“We found that sludge from the anaerobic system had a lower abundance of ARGs. Crucially, there was also a lower potential for the horizontal transfer of genes to opportunistic pathogens in the anaerobic system compared to the aerobic one,” says Sanchez Medina.
The team also examined the diversity in the types of antibiotic resistance for each system. Aerobic sludge had a higher diversity of potentially harmful ARGs, including those that confer resistance to broad-spectrum antibiotics like quinolones and tetracycline. Anaerobic sludge had fewer mobile genetic elements and the conditions within the system were less conducive to gene transfer.
“Coupled with the other advantages of anaerobic membrane bioreactors – lower overall sludge waste and lower energy requirements – this technology may be especially useful in the fight against antimicrobial resistance,” notes Hong.
“We plan to conduct a further, long-term study of anaerobic versus aerobic systems to gain more insights into the risk of antibiotic resistance dissemination and the downstream impacts in terms of reusing treated wastewater, which is a vital consideration for an arid country such as Saudi Arabia,” concludes Sanchez Medina.
