Chatterboxes: Researchers develop new model that shows how bacteria communicate

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Credit: Pixabay/CC0 Public Domain

When bacteria interact, they give off cellular signals that can trigger a response in their neighbors, causing them to behave in different ways or produce different substances. For example, they can communicate to coordinate movement away from danger or to emit light to ward off predators.

In new research published by Biophysical Reports, researchers from Florida State University and Cleveland State University lay out a mathematical model that explains how bacteria communicate within a larger ecosystem. By understanding how this process works, researchers can predict what actions might elicit certain environmental responses from a .

“Typically, models of bacteria in synthetic environments have involved many, many equations describing many, many things, but they weren’t really flexible for different applications,” said co-author Bhargav Karamched, an assistant professor in FSU’s Department of Mathematics and the Institute of Molecular Biophysics. “What my collaborators and I have done is to create a flexible that can be applied to a variety of experimental settings.”

Models like the one developed by Karamched’s team help to predict how those bacterial communities coordinate activity, allowing designers to adjust the parameters of a community, such as the population sizes of different types of bacteria or , and tailor them for different purposes. For example, in a population of two kinds of bacteria, having more of one kind of bacteria can be dangerous for a while having more of the other can be beneficial. Getting the right mix is crucial, and models help researchers design and analyze the they create.

“What’s lacking in right now are these general, flexible models that are ready off-the-shelf,” Karamched said. “This may not capture all the details in a bacteria community, but it still captures the general framework of what’s going on. Scientists and engineers can use that to compare against their and move forward.”

The researchers also tested their model against previously published research that examined how bacteria communicate across large spatial gaps. The previous research found that the only needed a positive feedback loop in order to signal to each other. But Karamched and his collaborators’ model predicts that the rate of production of signaling molecules must also be within a specific range for coordination to occur.

“This model lays the groundwork for a wide range of future experiments testing different strain interactions and geometries,” said co-author Shawn Ryan, an associate professor in the Department of Mathematics and Statistics and the co-director of the Center for Applied Data Analysis and Modeling at Cleveland State University.

Ryan Godin, a former Cleveland State University student and current Iowa State University doctoral student in chemical engineering, was the lead author on this paper.

More information:
Ryan Godin et al, The space between us: Modeling spatial heterogeneity in synthetic microbial consortia dynamics, Biophysical Reports (2022). DOI: 10.1016/j.bpr.2022.100085

Chatterboxes: Researchers develop new model that shows how bacteria communicate (2023, January 26)
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Kill dates for re-exposed black mosses

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Cape Rasmussen, one of the study sites mentioned in the paper. Credit: Derek J. Ford.

In their new paper for the Geological Society of America journal Geology, Dulcinea Groff and colleagues used radiocarbon ages (kill dates) of previously ice-entombed dead black mosses to reveal that glaciers advanced during three distinct phases in the northern Antarctic Peninsula over the past 1,500 years.

The terrestrial cryosphere and biosphere of the Antarctic Peninsula are changing rapidly as “first responders” to polar warming. We know from other studies that large of the Antarctic Peninsula are responding quickly to warmer summer air temperatures, and scientists have modeled that the glaciers expanded in the past because of , and not increased precipitation. However, we know much less about how this plays out at sea level where ice, ocean, and sensitive coastal life interact. Knowing when glaciers advanced and retreated in the past would improve our understanding of biodiverse coastal ecosystems—thriving with seals, penguins, and plants—and their sensitivity in the Antarctic Peninsula. One of the limitations of reconstructing glacier history is that there are not that many types of terrestrial archives we can use to constrain past glacier behavior. Re-exposed dead plants, abandoned penguin colonies, and rocks can be dated to better know the timing of permanent snow or glacier advance in the past.

Mosses are one of the few types of plants living in Antarctica and can get overridden and killed by advancing glaciers. The timing of when the glacier killed the moss provides an archive of glacier history. For example, when glaciers expand or advance, they can entomb or cover the plant—starving it of light and warmth. The date the plant died is the same time the glacier advanced over that location. As glaciers recede, these previously entombed mosses are exposed and are dead and black. “What’s so valuable about these kill dates compared to other records (like the ages of glacial erratics or penguin remains) is their accuracy,” says Groff. They provide a clearer picture of the climate history owing to their direct carbon exchange with the atmosphere and decreased error around the age estimate.

Drone video of Cape Rasmussen, northern Antarctic Peninsula, by Derek J. Ford. Credit: Derek J. Ford

Groff and colleagues collected black mosses around the northern Antarctic Peninsula by exploring the edges of glaciers and nunataks at several locations. By radiocarbon dating the mosses, they found that glaciers advanced three times in the past 1,500 years. This is evidence for phases of cooler and potentially wetter conditions than today. On Anvers Island, they learned that the last time the glacier was at its 2019 position was around 850 years ago as it expanded over the course of several centuries. Their estimates of glacier advance are much slower than recent retreat. “Interestingly, we found that the glacier front with the fastest advance also had the fastest retreat, suggesting that hotspots of rapid coastal glacier dynamics occur in the Antarctic Peninsula, says Groff.

Cape Rasmussen, one of the study sites mentioned in the paper. Credit: Derek J. Ford.

This is a unique dataset because it’s rare to have past net advance rates in the literature because glacial records tend to be destroyed when the glacier advances. These black mosses can reliably be used to estimate glacier advances in the past. “There are other lines of evidence that support our moss kill dates for past cooler conditions, such as peat records indicating lower biological productivity, as well as evidence for sea-level change from raised beaches as a result of changing ice mass. It’s also possible that the that led to glacier advances involved and would have had a negative impact on penguins, as we know they do today. Many of the recent abandoned penguin colonies are the same age as our youngest black moss,” says Groff.

More information:
Dulcinea V. Groff et al, Kill dates from re-exposed black mosses constrain past glacier advances in the northern Antarctic Peninsula, Geology (2023). DOI: 10.1130/G50314.1

Kill dates for re-exposed black mosses (2023, January 26)
retrieved 26 January 2023

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part may be reproduced without the written permission. The content is provided for information purposes only.

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Researchers report on metal alloys that could support nuclear fusion energy

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Extraordinarily tough and strong materials are required to withstand high heat and radiation inside nuclear fusion reactors, such as the one seen here. Credit: Korea Institute of Fusion Energy

At the end of 2022, researchers at Lawrence Livermore National Laboratory announced they had observed a net energy gain through nuclear fusion for the very first time. This monumental milestone toward fusion energy represents a huge leap forward in powering our homes and businesses with the carbon-neutral energy source. But converting this scientific achievement into a practical power source also requires new technologies to make a fusion-powered society a reality.

Scientists at Pacific Northwest National Laboratory (PNNL) and Virginia Polytechnic Institute and State University (Virginia Tech) are helping bring this goal to fruition through their materials research efforts. Their recent work, published in Scientific Reports, makes the case for tungsten heavy alloys and shows how they can be improved for use in advanced reactors by mimicking the structure of seashells.

“This is the first study to observe these material interfaces at such small length scales,” said Jacob Haag, first author of the research paper. “In doing so we revealed some of the fundamental mechanisms which govern material toughness and durability.”

Hexbyte Glen Cove Withstanding the heat

The sun—with a core temperature of around 27 million degrees Fahrenheit—is powered by nuclear fusion. Thus, it should come as no surprise that fusion reactions produce a lot of heat. Before scientists can harness fusion energy as a power source, they need to create advanced nuclear fusion reactors that can withstand high temperatures and irradiation conditions that come with fusion reactions.

Of all the elements on Earth, tungsten has one of the highest melting points. This makes it a particularly attractive material for use in fusion reactors. However, it can also be very brittle. Mixing tungsten with small amounts of other metals, such as nickel and iron, creates an alloy that is tougher than tungsten alone while retaining its high melting temperature.

It isn’t just their composition that gives these tungsten heavy alloys their properties—thermomechanical treatment of the material can alter properties like and fracture toughness. A particular hot-rolling technique produces microstructures in tungsten heavy alloys that mimic the structure of nacre, also known as mother-of-pearl, in seashells. Nacre is known to exhibit extraordinary strength, in addition to its beautiful iridescent colors. The PNNL and Virginia Tech research teams investigated these nacre-mimicking tungsten heavy alloys for potential nuclear fusion applications.

“We wanted to understand why these materials exhibit nearly unprecedented mechanical properties in the field of metals and alloys,” said Haag.

Hexbyte Glen Cove Examining microstructures for major toughness

To get a closer look at the microstructure of the alloys, Haag and his team used advanced materials characterization techniques, such as scanning transmission electron microscopy to observe atomic structure. They also mapped the nanoscale composition of the material interface using a combination of energy dispersive X-ray spectroscopy and atom probe tomography.

Within the nacre-like structure, the tungsten heavy alloy consists of two distinct phases: a “hard” phase of almost pure tungsten, and a “ductile” phase containing a mixture of nickel, iron, and tungsten. The research findings suggest that the high strength of tungsten heavy alloys comes from an excellent bond between the dissimilar phases, including intimately bonded “hard” and “ductile” phases.

“While the two distinct phases create a tough composite, they pose significant challenges in preparing high-quality specimens for characterization,” said Wahyu Setyawan, PNNL computational scientist and co-author of the paper. “Our team members did an excellent job in doing so, which enable us to reveal the detail structure of interphase boundaries as well as the chemistry gradation across these boundaries.”

The study demonstrates how crystal structure, geometry, and chemistry contribute to strong material interfaces in heavy alloys. It also reveals mechanisms to improve material design and properties for fusion applications.

“If these bi-phase alloys are to be used in the interior of a nuclear reactor, it is necessary to optimize them for safety and longevity,” said Haag.

Hexbyte Glen Cove Building the next generation of fusion materials

The findings presented in this study are already being further expanded upon in many dimensions within PNNL and in the scientific research community. Multiscale material modeling research is underway at PNNL to optimize structure, chemistry, and test the strength of dissimilar material interfaces, as well as experimental investigations to observe how these materials behave under the extreme temperatures and irradiation conditions of a fusion reactor.

“It is an exciting time for fusion energy with renewed interests from the White House and the private sectors. The research that we do in finding material solutions for prolonged operations is critically needed to accelerate the realization of reactors.” said Setyawan.

Additional PNNL authors are Jing Wang (formerly of PNNL), Karen Kruska, Matthew Olszta, Charles Henager, Danny Edwards, and Mitsu Murayama, who also holds a joint appointment with Virginia Tech.

More information:
J. V. Haag et al, Investigation of interfacial strength in nacre-mimicking tungsten heavy alloys for nuclear fusion applications, Scientific Reports (2023). DOI: 10.1038/s41598-022-26574-4

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