Mention “peat moss,” and many people will conjure up the curly brown plant material that gardeners use. “Oh, the thing you get at Home Depot” – is a common reaction Joel Kostka receives when he mentions that he studies peat moss. His response: “Peat moss is a really cool plant that’s important to the global carbon cycle.”

Joel Kostka is a professor in the School of Biological Sciences and the School of Earth and Atmospheric Sciences at Georgia Tech. The National Science Foundation has just awarded him and three co-principal investigators a $1.15 million, three-year grant to study the microbes in peat moss. The goal is to understand the microbiome’s role in nutrient uptake and the methane dynamics of wetlands and the impact of climate change on these activities.

Kostka’s collaborators are Jennifer Glass, an assistant professor in the Georgia Tech School of Earth and Atmospheric Sciences; Xavier Mayali, a research scientist at Lawrence Livermore National Laboratory; and David Weston, a staff scientist at Oak Ridge National Laboratory.

“It has been shown that microbes that live with peat moss help them to grow better by aiding their uptake of carbon and major nutrients such as nitrogen,” Kostka says. “This project will explore which microbes help to keep peat moss plants healthy, how plants and microbes interact, and how these relationships will be affected by climate change?”

Peat moss, also called Sphagnum, carpets the surface of peatlands. This type of wetland locks up huge amounts of carbon in the form of thick, peat soil deposits. When peat is broken down by microbes, greenhouse gases – methane and carbon dioxide – are produced. Methane is of particular interest, because when released to the atmosphere, it has a warming potential that is 21 times that of carbon dioxide.

Scientists hypothesize that environmental warming could cause peatlands to release a lot more methane, which in turn would accelerate climate change.    

“Our project is fundamental science. We’re trying to figure out how the microbes help the plants grow better.”

Lots of evidence suggest that peatlands will produce more methane as the environment warms up. “Methanogens [methane-producing bacteria] don’t like the cold,” Kostka says. “The warmer it gets, the better they are in producing methane.”

Methane in peatlands bubbles up to the peat moss layer. Methane-consuming microbes in peat moss eat some of the gas released. In effect, microbes in peat moss comprise a biofilter that reduces the amount of methane reaching the atmosphere.

However, “we hypothesize that the methane-eating microbes in peat moss may crash as the climate gets warmer,” Kostka says.  That sets up a double-whammy scenario: As the climate gets warmer, microbes in peatlands produce more methane, while other microbes in peat moss become less able to consume the greenhouse gas. “We could get an explosion of methane much more than we can predict,” Kostka says.   

Information about plant microbiomes is scant. Most plants whose microbiomes are being studied are crops, like corn and soybeans. “Few studies are available on plants that are environmentally important but not so economically important,” Kostka says. “A lot of our work is to build better models for how these wetlands respond to climate change.”

“Few studies are available on plants that are environmentally important but not so economically important. A lot of our work is to build better models for how these wetlands respond to climate change.”

Georgia Tech’s Glass will study the geochemical aspects of the peat moss microbiome. She will measure how fast peat moss microbes fix nitrogen and consume methane. She will also identify the trace nutrients available to peat moss in the wetland.

“Because these peatlands receive most of their nutrient input from precipitation, they contain extremely low concentrations of some bioessential trace metals,” Glass says. “We're interested in testing how trace nutrient availability impacts the growth of methane-cycling microbes exposed to warming temperatures.”

At Lawrence Livermore National Laboratory, Mayali will use NanoSims, an imaging mass spectrometer, to identify what microbes are eating the methane or fixing nitrogen. He will incubate microbe samples with substrates – methane, carbon dioxide, and nitrogen – enriched in rare isotopes such as carbon-13 instead of the normally abundant carbon-12. Analysis by NanoSims creates isotope maps that enables detailed tracing of who did what.

“Our instrument is able to not only track who is eating the methane or fixing nitrogen from the air, but more importantly, how much and where it ultimately ends up, for example into the Sphagnum plant versus being kept by the microbes,” Mayali says.

Meanwhile, at Oak Ridge National Laboratory, Weston will use genetically characterized peat moss and microbial members to construct synthetic communities to test how host moss genes influence microbiome assembly and functioning. “Peat moss microbiomes are extremely complex with thousands of members with diverse metabolic capabilities,” Weston says.

“To help determine the role of specific community member interactions,” Weston adds, “we will decompose the field system into simplified synthetic communities where community changes and nutrients can be accurately measured and subjected to precise environmental manipulations.”

“We can engineer wetlands to encourage the growth of peat moss, but that’s not our goal,” Kostka says. “Our project is fundamental science. We’re trying to figure out how the microbes help the plants grow better.”

Data, data, and more data.

The rapid growth of data seems wild and limitless. But various Transdisciplinary Research in Principles of Data Science (TRIPODS) institutes have been making theoretical sense of it.

TRIPODS institutes receive funding from the National Science Foundation (NSF). Among them is Georgia Tech’s TRIAD – the Transdisciplinary Research Institute for Advancing Data Science. TRIAD researchers are poised to share data science insights with the Atlanta higher education community.

Meanwhile, NSF aims to expand the scope of TRIPODS institutes. Today the agency awarded 19 collaborative projects at 23 universities. The awards are called TRIPODS+X grants. X is the scope-expanding activity; it could be research, visioning, or education.

Among the award recipients is Georgia Tech’s project: TRIPODS+X:EDU Collaborative Education: Data-driven Discovery and Alliance, led by Prasad Tetali, a professor of mathematics and computer science at Georgia Tech.

The award to Georgia Tech and its alliance partners – Agnes Scott, Morehouse, and Spelman Colleges – aims to train a diverse workforce for the inevitable data-driven future. The project will also engage faculty at the minority-serving institutions to help them teach data science and develop related curricula.

"TRIPODS+X is exciting not only for its near-term impact addressing some of society's most important scientific challenges, but [also] because of its potential for developing tools for future applications," says Anne Kinney, NSF assistant director Mathematical and Physical Sciences. 

With the $200,000 TRIPODS+X:EDU grant, the alliance partners will develop undergraduate data-science-focused courses. Through boot camps, workshops, and other joint activities, they will prepare data science modules to integrate into science curricula at the partner institutions. The goal is to prepare students who can address the emerging challenges in data science.

“The NSF-supported educational alliance is exciting in many ways,” says Prasad Tetali.

“It gives an opportunity to infuse the foundational data science curriculum with real-world applications from the physical and life sciences,” Tetali says. “It will also likely catalyze collaborative research in data science and related fields between Georgia Tech and Atlanta area colleges.”  

Following are the individuals involved in the TRIPODS+X: EDU project:

Principal Investigators

• Chris DePree, Agnes Scott College
• Alan Koch, Agnes Scott College
• Wenjing Liao, Georgia Tech School of Mathematics
• Brandeis Marshall, Spelman College       
• Chuang Peng, Morehouse College
• David Sherrill, Georgia Tech School of Chemistry and Biochemistry
• Prasad Tetali, Georgia Tech School of Mathematics and School of Computer Science
• Joshua Weitz, Georgia Tech School of Biological Sciences

Senior Personnel

• Thinh Doan, Georgia Tech School of Electrical and Computer Engineering
• Flavio Fenton, Georgia Tech School of Physics
• Xiaoming Huo, Georgia Tech School of Industrial and Systems Engineering
• Renata Rawlings-Goss, Georgia Tech Institute for Data Engineering and Science
• Justin Romberg, Georgia Tech School of Electrical and Computer Engineering

Photo Caption

From left to right, top row: Joshua Weitz, Justin Romberg, and David Sherrill; middle row: Alan Koch, Brandeis Marshall, Chris DePree, and Wenjing Liao; bottom row: Thinh Doan, Prasad Tetali, and Chuang Peng

They may look a little like space capsules, but nuclear magnetic resonance spectrometers stay planted on the floor and use potent magnetism to explore opaque constellations of molecules.

Three Atlanta area universities jointly launched a nuclear magnetic resonance collaboration called the Atlanta NMR Consortium to optimize the use of this technology that provides insights into relevant chemical samples containing so many compounds that they can otherwise easily elude adequate characterization. The consortium has been operating since July 2018.

Crab pee

Take, for example, crab urine. It’s packed with hundreds to thousands of varying metabolites, and researchers at the Georgia Institute of Technology wanted to nail down one or two of them that triggered a widespread crab behavior. Without access to NMR they may not have found them at all even after an extensive search.

The spectrometer pulled the right two needles out of the haystack, so the researchers could test them on the crabs and confirm that they were initiating the behavior.

Emory University, Georgia State University and Georgia Tech already have NMR technology, but the Atlanta NMR Consortium will enable them to fully exploit it while cost-effectively staying on top of upgrades.

“NMR continues to grow and develop because of technological advances,” said David Lynn, a chemistry professor at Emory University.

That means buying new machines every so often, and one new NMR spectrometer can run into the millions; annual maintenance for one machine can cost tens of thousands of dollars. Thus, reducing costs and maximizing usage makes good sense.

Medicine, geochemistry

The human body, sea-side estuaries, and rock strata present huge collections of compounds. NMR takes inventory of complex samples from such sources via the nuclei of atoms in the molecules.

A nucleus has a spin, which makes it magnetic, and NMR spectrometry’s own powerful magnetism detects spins and pinpoints nuclei to feel out whole molecules. These can be large or small, from mineral compounds with three or four component atoms to protein polymers with tens of thousands of parts.

Researchers in medicine, biochemistry, ecology, geology, food science – the possible list is exhaustive -- turn to NMR to untangle their particular molecular jungles. The consortium wants to leverage that diversity.

“As we go in different directions, we will benefit from a cohesive community of people who know how to use NMR for a wide range of problems,” said Anant Paravastu, an associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering.

“The most important goal for us is the sharing of our expertise,” said Markus Germann, a professor of chemistry at Georgia State.

Consortium members will benefit the most from the pooled NMR resources, but non-partners can also book access. Read more about the Atlanta NMR Consortium here on Georgia Tech’s College of Sciences website

Episode 4 of ScienceMatters' Season 1 stars Nastassia Patin. Listen to the podcase here and read the transcript here!

Massive whale sharks headline the Ocean Voyager exhibit at Georgia Aquarium.  Its tiniest residents are the ones that concern Nastassia Patin. Patin is a postdoctoral researcher working in the lab of Frank Stewart. Stewart is an associate professor in the School of Biological Sciences and a member of Georgia Tech's Parker H. Petit Institute for Bioengineering and Bioscience.

Patin's research interests are microbial ecology, environmental microbiology, chemical ecology, metagenomics. Episode 4 describes her findings after studying the microbiome of the Ocean Voyage exhibit at Georgia Aquarium.  What she’s learning may help keep all aquariums clear and healthy.

Take a listen at sciencematters.gatech.edu.

Enter to win a prize by answering the question for Episode 4:

What is the name of the Georgia Aquarium sea turtle mentioned in Episode 4?

Submit your entry by 11 AM on Monday, Sept. 17, at sciencematters.gatech.edu. Answer and winner will be announced shortly after the quiz closes.

On Sept. 13, starting at 11 A.M., mathematicians, musicians, and dancers will breathe life into the classic problem known as the Seven Bridges of Königsberg (7BK). The interactive exposition and performance celebrates this problem’s journey from 18th-century Prussia, in the small town of Königsberg, to 21st-century Atlanta.

On the Georgia Tech campus is a representation of Königsberg and the seven bridges that connect its four land masses, which are divided by a river. The rendition – along the Atlantic Drive Promenade, on a site called the Seven Bridges Plaza – affirms that art, science, and mathematics are but different ways to grasp the world.

The Sept. 13 music and dance performance – The Seven Bridges of Königsberg – especially hopes to demystify and humanize mathematics, says Evans Harrell, an emeritus professor in the School of Mathematics.

The event begins with an interactive exposition by members of the Georgia Tech student organization Club Math. On each of the four land masses representing Königsberg, Club Math members will be at stations to discuss the 7BK problem; the life and times of Leonhard Euler, whose solution to the 7BK problem gave birth to graph theory; the role of graph theory in the modern world, and a special aspect of graph theory called the four-color theorem.

“Our project is also an experiment about how scientific stories can be told and about how the sciences can inspire original art.”

Euler, the Seven Bridges, and Graph Theory

The 7BK problem asks: Can one walk around Königsberg, crossing each of the seven bridges exactly once?

The Swiss mathematician Leonhard Euler proved that it is impossible to cross each of the seven bridges of Königsberg only once. The proof considered not only the case of Königsberg, but all possible ways a city could be connected by bridges and when it is possible to cross each bridge only once. In developing the proof, Euler invented a new field of mathematics, now called graph theory.

Euler’s insight was to simplify the problem, says Georgia Tech mathematics professor Dan Margalit. Graph theory reduces the problem to one about points – called vertices – and the lines – called edges – connecting them. The vertices correspond to the land masses and the edges are the bridges. The 7BK problem thus rendered, it is not hard to see  the answer.

Margalit explains: Any attempted solution has two variations. In the first case, the journey starts and ends at the same land mass. Here, the number of bridges – or edges – associated with each land mass – or vertex – is even. Because every arrival at a land mass comes with a departure, every vertex has an even number of edges. Therefore any continuous path uses an even number of edges at each vertex. This is impossible in Königsberg because each land mass has an odd number of bridges.

In the second case, the journey ends in another place from where it started. Again the number of edges at each vertex must be even except at the start and end. Because to leave the start requires only one bridge, as does arriving at the end. Therefore, at the start and end vertices, the total number of edges will be an odd number. But at all other vertices, the number of edges would be even, as before. 

Again this is impossible in Königsberg, because all the land masses have an odd number of bridges.

Graph theory permeates the modern world. “Facebook is a graph: vertices are people and edges are friendships," Margalit says. "Graph theory has many other applications all over science and mathematics."

“Facebook is a graph: vertices are people and edges are friendships.”

Math in Motion

For the Sept. 13 performance, Harrell partnered with the Georgia Tech School of Music’s Chaowen Ting. She will conduct the Georgia Tech Symphony Orchestra in performing original music by composer Marshall Coats. The music will accompany dances choreographed by artistic director Kristel Tedesco.

In a behind-the-scenes video, Tedesco says she recognized the similar struggles of mathematicians and artists working in imaginary worlds “and trying to find truth within them.” The resulting performance, she adds, aims to spark and stimulate the public’s curiosity about mathematics.

“We wish to engage the public in the wonder of mathematics and science, of music and dance, and the surprising ways that they can work together,” Harrell says. “Our project is also an experiment about how scientific stories can be told and about how the sciences can inspire original art.”

Support for the event came from Science in Vivo and Georgia Tech's College of Design, College of Sciences, and Office of the Arts.

Editor’s Note: This story was written by Emily Woodward, public relations coordinator for Marine Extension and Georgia Sea Grant. It was originally published in the UGA Marine Extension and Georgia Sea Grant Newsletter Volume 4, issue 5.

Four coolers, two shovels, countless sampling vials and five people pile into a vehicle headed to a secluded salt marsh on Sapelo Island, Georgia. It’s a surprising amount of equipment needed to study the microscopic community of organisms responsible for the health of Georgia’s most abundant coastal habitat, the salt marsh.   

“Plant microbiome research, I always say, is about 10 years behind human microbiome research,” says Joel Kostka, jointly appointed professor of biology and earth and atmospheric sciences at Georgia Institute of Technology.

Roughly half of the cells in the human body are microbial. These microbes, mostly bacteria, all have different functions; some make us ill, but most keep us healthy by helping with digestion or preventing infection. Together, these microorganisms make up the human microbiome.

The same is true in the plant world, though little is known about plant microbiomes, particularly those associated with salt-tolerant coastal plants like Spartina alterniflora, which dominate Georgia’s salt marshes.  

With funding from Georgia Sea Grant, Kostka is studying the microbes intimately associated with Spartina to better understand how the plant microbiome supports the health of Georgia’s salt marshes.

“In a way, this is discovery-based science because no one has studied the microbes that are intimately associated with these plants,” says Kostka. “When you look at the marsh from a large scale it really looks constant and consistent, but when you get down at the micro level you see all kinds of differences. There's a lot of complexity there.”

The research team wants to know how the microbial community changes as you move from the interior of the marsh, where the growth of Spartina is stunted and the plants are short, to the taller, lush marsh growing near the tidal creeks.

At the site, they measure salinity, oxygen, and pH as well as the height and density of Spartina at different spots along a transect. A hole punch is used to collect samples of Spartina blades, which will be measured for nutrients, like phosphorous and nitrogen. Soil samples and root material are taken back to the lab where the latest gene sequencing and metagenomics methods will be used to identify individual microbes and understand the microbial processes that improve the health of the plant. 

“We have a number of parameters that we can measure to determine whether the plants are healthy, and then we go in and look at the microbes in more healthy plants versus less healthy plants, and see how those microbes are changing,” says Kostka.

It’s a lot of data to collect and the work isn’t easy, especially when trudging through knee-high marsh mud in 90-degree temperatures.

Luckily, Kostka has an extra set of hands to help with the sampling.

Elisabeth Pinion, an AP environmental science teacher from Cumming, Georgia, is working alongside Kostka and his team. Pinion is one of 16 educators participating in Schoolyard Program of the NSF-supported Georgia Coastal Ecosystems (GCE) Long Term Ecological Research (LTER) Project, which is hosted every summer at the University of Georgia Marine Institute on Sapelo Island. As part of the program, teachers spend a week on the coast, shadowing different researchers in the field and learning about sampling methods and processes that can be taken back to the classroom.

Pinion recognized similarities between the topics she covers in class and the research methods used for this project.

“Studying parameters that determine the productivity of different ecosystems is something that we generally spend a lot of time on,” says Pinion. “What they are looking at is very applicable to the classroom.”

Throughout the week, Kostka will have the opportunity to engage multiple educators in the field, showing him or her how they collect samples for microbiology and discussing the important ecosystem services that salt marshes provide.

"The Schoolyard Program is a great way to give the teachers a behind-the-scenes look at how science is conducted, including sometimes having to rethink your strategy once you get out in the field," said Merryl Alber, professor of marine sciences at UGA and lead PI of the GCE LTER project. "It’s also beneficial for researchers, who have a chance to interact with the teachers and think creatively about how to bring the science back into the classroom.”

Kostka recognizes the importance of making his research accessible to educators and students, which is why he used a portion of his Georgia Sea Grant funding to support three of the educators participating in the Schoolyard Program.

The trip to Sapelo is the first of many trips the research team will make to the coast. They plan to sample sites at two other barrier islands; Tybee Island and St. Simons Island, in the coming months.

Kostka hopes results from the project can be used to develop innovative methods for improving salt marsh restoration practices in Georgia. One example would be to create plant probiotics that could be applied to Spartina seedlings when planting new marshes.

“We could grow beneficial microbes in the lab and add them to the naked roots during planting, which would help the plant to take hold in the intertidal zone,” says Kostka.

“With sea level rise and increased coastal development, restoration activities will be more important to maintaining the productivity of Georgia’s marshes,” says Mark Risse, director of Marine Extension and Georgia Sea Grant.  

“Funding research like this, that helps us improve attempts to establish native vegetation, will inform future restoration projects and hopefully make them more economically and environmentally efficient.”

Episode 3 of ScienceMatters' Season 1 stars M.G. Finn. Listen to the podcast and read the transcript here!

Leishmaniasis is a scary parasitic disease; it can rot flesh. Formerly contained in countries near the equator, it has arrived in North America. School of Chemistry and Biochemistry Professor and Chair M.G. Finn explains why it’s so tough to fight this disease. His collaboration with Brazilian researcher Alexandre Marques has raised hopes for a possible vaccine.

Follow the the researchers' journey at sciencematters.gatech.edu.

Enter to win a prize by answering the episode's question:

What sugar molecule mentioned in Episode 3 is the main reason surgeons can’t transplant organs from animals into humans?

Submit your entry by noon on Friday, Sept. 7, at sciencematters.gatech.edu. Answer and winner will be announced on Monday, Sept. 10.

Results of Episode 2 Quiz

Q: What small four-legged animals mentioned in Episode 2 help Jenny McGuire collect bones from Natural Trap Cave?

A: Wood rats, pack rats, or rats

The winner is Pedro Marquez Zacarias. He was listening to ScienceMatters while doing routine data analysis for his research.

A third-year Ph.D. student in the Georgia Tech Quantitative Biosciences Graduate Program, Marquez Zacarias aims to add to the understanding of how biological complexity evolved, particularly multicellularity.

Marquez Zacarias comes from a small town in rural México, an indigenous community called Urapicho, in the state of Michoacán.

Editor's Note: This story by Victor Rogers was originally published on the Georgia Tech News Center on Aug. 8, 2018.

When Will Ratcliff and Peter Yunker first met for coffee they had no idea they would eventually collaborate on research that would be published in Nature Communications and Nature Physics.

Ratcliff, an assistant professor in the School of Biological Sciences, arrived at Tech in January 2014. Yunker, an assistant professor in the School of Physics, arrived in January of the following year.

“I met with [Physics Professor] Dan Goldman and told him about my interests in biophysics,” said Yunker. “He told me there’s another young guy who just arrived. You should contact him.”  

Yunker reached out to Ratcliff, and the two began meeting weekly for coffee in the basement of the College of Computing.

“I think our conversations for a solid six months were just about friend stuff,” Ratcliff said. “We talked about science, but we weren’t actively pursuing projects. We were just hanging out and getting to know each other.”

Yunker said they discussed ideas about the evolution of multicellularity.

“Will would talk a little about the biology of the evolution of multicellularity. And then we would pivot, and I would talk about the physics of multicellularity,” Yunker said. 

Though coming from different disciplines — biology and physics — Ratcliff and Yunker quickly recognized some common ground.  

“I would say, ‘There’s this thing in biology where this needs to happen,’ and he would say ‘there’s this thing in physics where this needs to happen,’” Ratcliff said. “It would blow my mind because it was a totally different way of thinking about the things that I was already thinking about. It was incredibly exciting because there were these parallels coming from such different places, and they were describing the same overlapping material. I think we both could tell there was a lot of cool stuff to be done.”

The harder part was figuring out where the overlap was concrete so they could actually conduct experiments or write models.

“A lot of our conversations are brainstorming style,” Yunker said. “They’re less about knocking down ideas and more about: ‘Let’s get a lot of information out there so we can find where that concrete idea emerges.’”  

The collaboration also eased the pressure of being a new faculty member.

“It’s nice to work with other people who are at a similar level, to bounce ideas off each other, talk about critical review, and vent about frustrations,” Yunker said. “The whole time I’ve been here I have always heard Georgia Tech is very supportive of collaboration. I’ve heard of other places where that support isn’t there when you’re still at the assistant professor level. I haven’t worried at all about if there will be trouble down the line if we collaborate. Instead, I see it as we’re doing the best science, and that’s what Georgia Tech wants.”

Ratcliff said, “That’s one of Georgia Tech’s real strengths. People really appreciate our collaboration. I hear from people in both communities — biology and physics. They appreciate not just the research, but also the strengthening of the bridge between the departments and the sense of community it builds.”

In addition to their research collaborations, Ratcliff and Yunker co-advise a Ph.D. student and a postdoc.

Collaboration Advice to New Faculty

Yunker and Ratcliff make collaboration look deceptively easy.

“Collaboration takes effort. It takes sustained interaction,” Ratcliff said. “There’s got to be a reason to do that because as new professors we’re super busy trying to get everything off the ground: get your lab running, get grants, write papers, design classes, do service work. We’re spread really thin. So, to have sustained interactions that are needed for a good collaboration, you have to prioritize it and want to do it.”

Yunker added, “One of the best approaches when starting a new collaboration is to either let it grow or die on its own. If the idea isn’t there or if you just don’t mesh, then forcing it is going to be difficult for everyone.”

Ratcliff has advice for new faculty who are interested in collaborating.

“It’s really exciting and valuable to have a close collaborator from a different discipline or with a  different skillset,” he said. “To get that, I suggest forming collaborations with other professors who are about your age. Key reasons are you’re both at the same stage in your careers. You’re equals. Also, a new professor is likely to have time to form new collaborations. Lastly, new professors have startup funds and a large degree of flexibility. This is great for trying things that are risky.”

He also suggests attending receptions for new faculty.

“Talk to people outside of your discipline. Don’t spend all of your time at the mixer talking to your departmental colleagues,” Ratcliff said.

Developing a good collaboration can be transformational.

“Our collaboration has fundamentally reshaped the way I think about key problems in my field,” Ratcliff said. “I know how to think about the things I was trained to think about, but I had no idea how to think about things I wasn’t trained to think about.”

Yunker said, “Together we’re able to ask and answer more interesting questions. I was not versed at all on questions about evolutionary transitions and individuality. I wasn’t aware of all the open questions and problems there, and they’re fascinating. By coming together, we end up asking even more interesting questions and, hopefully, coming up with new approaches.”

Ratcliff said what made the collaboration work is that he and Yunker became friends.

“We enjoy hanging out. I look forward to having coffee,” Ratcliff said. “We have these exciting scientific discussions where it was obvious that there’s something there, but we had to make the ideas touch down to reality.”

Episode 2 of ScienceMatters' Season 1 stars Jenny McGuire. The assistant professor in the School of Earth and Atmospheric Sciences and the School of Biological Sciences has a tough commute to her summer research site: An 80-foot drop into Wyoming’s deep, dark Natural Trap Cave. There she collects fossils that she hopes will yield clues about the impact of climate change on animal and human populations.

Follow her journey at sciencematters.gatech.edu.

Enter to win a prize by answering the episode's question:

What small four-legged animals mentioned in Episode 2 help Jenny McGuire collect bones from Natural Trap Cave?

Submit your entry by noon on Friday, Aug. 31, at sciencematters.gatech.edu. Answer and winner will be announced on Monday, Sept. 3.

Congratulations to Vineeth Aljapur, winner of Episode 1 quiz. Aljapur is a first-year student in the Georgia Tech Bioinformatics Graduate Program.  

As microorganisms evolve to resist antibiotics, the world risks running out of drugs to treat bacterial infections. One way to slow this trend is to find new modes of using existing drugs, even those now ineffective because of microbial resistance.

One strategy is based on the phenomenon of collateral sensitivity: When some microbes develop resistance to one antibiotic, they become hypersensitive to another. For example, when an Escherichia coli strain became indifferent to chloramphenicol, it also became highly vulnerable to polymyxin B. For this strain, chloramphenicol and polymyxin B form a collaterally sensitive pair.

Sometimes the drug pair exhibits mutual collateral sensitivity (MCS) for a pathogen: The pathogen’s evolution of resistance to drug A increases its sensitivity to drug B and vice versa.

Researchers have identified several MCS pairs for pathogens like E. coli and Pseudomonas aeruginosa. Some have proposed exploiting the phenomenon to treat infections by cycling through the drugs, A-B-A-B.

“This sounds very clever,” says Georgia Tech biomathematician Howard “Howie” Weiss. “Bbut what could prevent this scheme from working is the rapid emergence and ascent of a population of cells that are resistant to both antibiotics.”

The prospect is exciting, but no experiments have yet been performed to test efficacy.

 “This was a real team effort between a microbiologist and a biomathematician.”

With Stockholm University microbiologist Klas Udekwu, Weiss has tested the plausibility of such schemes, using a mathematical model that considers factors affecting efficacy. Applying treatment protocols consisting of pairs MCS antibiotics, they examined how fast multiply-resistant mutants would emerge. They reported results in Drug Design, Development and Therapy.

They found some treatments that did not produce multiply-resistant mutants for several weeks, for several months, and even indefinitely. That means some combinations of an MCS pair prevented further development of the bacteria’s resistance to either drug.

 “This was a real team effort between a microbiologist and a biomathematician,” Weiss says. “My job was to construct the model using a system of differential equations and very carefully simulate their solution using a computer.” 

The first experiment used low to moderate concentrations of antibiotics and daily cycling: drug A on day 1, drug B on day 2, drug A on day 3. At these drug levels, treatment failed. Resistant mutants rapidly developed and dominated.

Simulation results improved with higher drug concentrations. “We found that one-day cycling of certain antibiotics kept the double-resistant mutants in check for over two weeks, which would be sufficient to cure many infections,” Weiss says.

The simulations also showed that three-day cycling of antibiotics that only inhibit bacterial growth – not kill – would never result in double-resistant mutants. “This was striking,” Udekwu says, “but in line with ecological theory.”

Udekwu is now conducting in-vitro cycling experiments. The next step would likely be experiments in mice. “It is far too early for clinicians to think about this strategy,” he says, “other than to keep an ear out for it, perhaps in a Cochrane report someday.