Saturday, August 1, 2020

Metal-Breathing Bacteria Could Transform Electronics, Biosensors, and More

When the Shewanella oneidensis bacterium “breathes” in certain metal and sulfur compounds anaerobically, the way an aerobic organism would process oxygen, it produces materials that could be used to enhance electronics, electrochemical energy storage, and drug-delivery devices.

The ability of this bacterium to produce molybdenum disulfide — a material that is able to transfer electrons easily, like graphene — is the focus of research published in Biointerphases by a team of engineers from Rensselaer Polytechnic Institute.

Credit; Rensselaer Polytechnic Institute.

“This has some serious potential if we can understand this process and control aspects of how the bacteria are making these and other materials,” said Shayla Sawyer, an associate professor of electrical, computer, and systems engineering at Rensselaer.

The research was led by James Rees, who is currently a postdoctoral research associate under the Sawyer group in close partnership and with the support of the Jefferson Project at Lake George — a collaboration between Rensselaer, IBM Research, and The FUND for Lake George that is pioneering a new model for environmental monitoring and prediction. This research is an important step toward developing a new generation of nutrient sensors that can be deployed on lakes and other water bodies.

“We find bacteria that are adapted to specific geochemical or biochemical environments can create, in some cases, very interesting and novel materials,” Rees said. “We are trying to bring that into the electrical engineering world.”

Rees conducted this pioneering work as a graduate student, co-advised by Sawyer and Yuri Gorby, the third author on this paper. Compared with other anaerobic bacteria, one thing that makes Shewanella oneidensis particularly unusual and interesting is that it produces nanowires capable of transferring electrons.

“That lends itself to connecting to electronic devices that have already been made,” Sawyer said. “So, it’s the interface between the living world and the manmade world that is fascinating.”

Sawyer and Rees also found that, because their electronic signatures can be mapped and monitored, bacterial biofilms could also act as an effective nutrient sensor that could provide Jefferson Project researchers with key information about the health of an aquatic ecosystem like Lake George.

“This groundbreaking work using bacterial biofilms represents the potential for an exciting new generation of ‘living sensors,’ which would completely transform our ability to detect excess nutrients in water bodies in real-time. This is critical to understanding and mitigating harmful algal blooms and other important water quality issues around the world,” said Rick Relyea, director of the Jefferson Project.

Sawyer and Rees plan to continue exploring how to optimally develop this bacterium to harness its wide-ranging potential applications.

“We sometimes get the question with the research: Why bacteria? Or, why bring microbiology into materials science?” Rees said. “Biology has had such a long run of inventing materials through trial and error. The composites and novel structures invented by human scientists are almost a drop in the bucket compared to what biology has been able to do.”

Contacts and sources:
Torie Wells
Rensselaer Polytechnic Institute

NASA Sun Data Helps New Model Predict Disruptive X-Class Solar Flares

Using data from NASA’s Solar Dynamics Observatory, or SDO, scientists have developed a new model that successfully predicted seven of the Sun’s biggest flares from the last solar cycle, out of a set of nine. With more development, the model could be used to one day inform forecasts of these intense bursts of solar radiation.

As it progresses through its natural 11-year cycle, the Sun transitions from periods of high to low activity, and back to high again. The scientists focused on X-class flares, the most powerful kind of these solar fireworks. Compared to smaller flares, big flares like these are relatively infrequent; in the last solar cycle, there were around 50. But they can have big impacts, from disrupting radio communications and power grid operations, to – at their most severe – endangering astronauts in the path of harsh solar radiation. Scientists who work on modeling flares hope that one day their efforts can help mitigate these effects.

Led by Kanya Kusano, the director of the Institute for Space-Earth Environmental Research at Japan’s Nagoya University, a team of scientists built their model on a kind of magnetic map: SDO’s observations of magnetic fields on the Sun’s surface. Their results were published in Science on July 30, 2020.

An X-class solar flare flashes on the edge of the Sun on March 7, 2012. This image was captured by NASA's Solar Dynamics Observatory and shows a type of light that is invisible to human eyes, called extreme ultraviolet light.

Credits: NASA's Goddard Space Flight Center/SDO

It’s well-understood that flares erupt from hot spots of magnetic activity on the solar surface, called active regions. (In visible light, they appear as sunspots, dark blotches that freckle the Sun.) The new model works by identifying key characteristics in an active region, characteristics the scientists theorized are necessary to setting off a massive flare.

The first is the initial trigger. Solar flares, especially X-class ones, unleash huge amounts of energy. Before an eruption, that energy is contained in twisting magnetic field lines that form unstable arches over the active region. According to the scientists, highly twisted rope-like lines are a precursor for the Sun’s biggest flares. With enough twisting, two neighboring arches can combine into one big, double-humped arch. This is an example of what’s known as magnetic reconnection, and the result is an unstable magnetic structure – a bit like a rounded “M” – that can trigger the release of a flood of energy, in the form of a flare.

Where the magnetic reconnection happens is important too, and one of the details the scientists built their model to calculate. Within an active region, there are boundaries where the magnetic field is positive on one side and negative on the other, just like a regular refrigerator magnet.

“It’s similar to an avalanche,” Kusano said. “Avalanches start with a small crack. If the crack is up high on a steep slope, a bigger crash is possible.” In this case, the crack that starts the cascade is magnetic reconnection. When reconnection happens near the boundary, there’s potential for a big flare. Far from the boundary, there’s less available energy, and a budding flare can fizzle out – although, Kusano pointed out, the Sun could still unleash a swift cloud of solar material, called a coronal mass ejection.

Kusano and his team looked at the seven active regions from the last solar cycle that produced the strongest flares on the Earth-facing side of the Sun (they also focused on flares from part of the Sun that is closest to Earth, where magnetic field observations are best). SDO’s observations of the active regions helped them locate the right magnetic boundaries, and calculate instabilities in the hot spots. In the end, their model predicted seven out of nine total flares, with three false positives. The two that the model didn’t account for, Kusano explained, were exceptions to the rest: Unlike the others, the active region they exploded from were much larger, and didn’t produce a coronal mass ejection along with the flare.

“Predictions are a main goal of NASA’s Living with a Star program and missions,” said Dean Pesnell, the SDO principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who did not participate in the study. SDO was the first Living with a Star program mission. “Accurate precursors such as this that can anticipate significant solar flares show the progress we have made towards predicting these solar storms that can affect everyone.”

While it takes a lot more work and validation to get models to the point where they can make forecasts that spacecraft or power grid operators can act upon, the scientists have identified conditions they think are necessary for a major flare. Kusano said he is excited to have a promising first result.

“I am glad our new model can contribute to the effort,” he said.

Contacts and sources:
By Lina Tran
NASA’s Goddard Space Flight Center,