In a new study published in Current Biology, researchers in Georgia Tech’s School of Biological Sciences have engineered one of the world’s first strains of yeast that may be happier with the lights on.
“We were frankly shocked by how simple it was to turn the yeast into phototrophs (organisms that can harness and use energy from light),” says Anthony Burnetti, a research scientist working in Associate Professor William Ratcliff’s laboratory and corresponding author of the study. “All we needed to do was move a single gene, and they grew 2% faster in the light than in the dark. Without any fine-tuning or careful coaxing, it just worked.”
Easily equipping the yeast with such an evolutionarily important trait could mean big things for our understanding of how this trait originated — and how it can be used to study things like biofuel production, evolution, and cellular aging.
The research was inspired by the group’s past work investigating the evolution of multicellular life. The group published their first report on their Multicellularity Long-Term Evolution Experiment (MuLTEE) in Nature last year, uncovering how their single-celled model organism, “snowflake yeast,” was able to evolve multicellularity over 3,000 generations.
Throughout these evolution experiments, one major limitation for multicellular evolution appeared: energy.
“Oxygen has a hard time diffusing deep into tissues, and you get tissues without the ability to get energy as a result,” says Burnetti. “I was looking for ways to get around this oxygen-based energy limitation.”
One way to give organisms an energy boost without using oxygen is through light. But the ability to turn light into usable energy can be complicated from an evolutionary standpoint. For example, the molecular machinery that allows plants to use light for energy involves a host of genes and proteins that are hard to synthesize and transfer to other organisms — both in the lab and naturally through evolution.
Luckily, plants are not the only organisms that can convert light to energy.
A simpler way for organisms to use light is with rhodopsins: proteins that can convert light into energy without additional cellular machinery.
“Rhodopsins are found all over the tree of life and apparently are acquired by organisms obtaining genes from each other over evolutionary time,” says Autumn Peterson, a biology Ph.D. student working with Ratcliff and lead author of the study.
This type of genetic exchange is called horizontal gene transfer and involves sharing genetic information between organisms that aren’t closely related. Horizontal gene transfer can cause seemingly big evolutionary jumps in a short time, like how bacteria are quickly able to develop resistance to certain antibiotics. This can happen with all kinds of genetic information and is particularly common with rhodopsin proteins.
“In the process of figuring out a way to get rhodopsins into multi-celled yeast,” explains Burnetti, “we found we could learn about horizontal transfer of rhodopsins that has occurred across evolution in the past by transferring it into regular, single-celled yeast where it has never been before.”
To see if they could outfit a single-celled organism with solar-powered rhodopsin, researchers added a rhodopsin gene synthesized from a parasitic fungus to common baker’s yeast. This specific gene is coded for a form of rhodopsin that would be inserted into the cell’s vacuole, a part of the cell that, like mitochondria, can turn chemical gradients made by proteins like rhodopsin into energy.
Equipped with vacuolar rhodopsin, the yeast grew roughly 2% faster when lit — a huge benefit in terms of evolution.
“Here we have a single gene, and we're just yanking it across contexts into a lineage that's never been a phototroph before, and it just works,” says Burnetti. “This says that it really is that easy for this kind of a system, at least sometimes, to do its job in a new organism.”
This simplicity provides key evolutionary insights and says a lot about “the ease with which rhodopsins have been able to spread across so many lineages and why that may be so,” explains Peterson, who Peterson recently received a Howard Hughes Medical Institute (HHMI) Gilliam Fellowship for her work. Carina Baskett, grant writer for Georgia Tech’s Center for Microbial Dynamics and Infection, also worked on the study.
Because vacuolar function may contribute to cellular aging, the group has also initiated collaborations to study how rhodopsins may be able to reduce aging effects in the yeast. Other researchers are already starting to use similar new, solar-powered yeast to study advancing bioproduction, which could mark big improvements for things like synthesizing biofuels.
Ratcliff and his group, however, are mostly keen to explore how this added benefit could impact the single-celled yeast’s journey to a multicellular organism.
“We have this beautiful model system of simple multicellularity,” says Burnetti, referring to the long-running Multicellularity Long-Term Evolution Experiment (MuLTEE). “We want to give it phototrophy and see how it changes its evolution.”
Citation: Peterson et al., 2024, Current Biology 34, 1–7.
DOI: https://doi.org/10.1016/j.cub.2023.12.044
Dunlap was hired earlier this year as the Urban Honey Bee Project's (UHBP) first-ever beekeeper in residence. Throughout her residency, she'll conduct research into the pollinator's place in our ecosystem and how beekeeping may offer relief to veterans dealing with post-traumatic stress disorder (PTSD), while connecting with the bees through art.
Dunlap had been gardening for over a decade, but in 2016, when she got the urge to find new ways to engage with nature, she recalled a powerful piece of imagery that shaped her childhood — Wu-Tang Clan's music video for “Triumph” and its depiction of the group's members as a powerful swarm of Africanized killer bees.
"The political messaging and tying Africanized killer bees in with the stereotypes and the tropes of African Americans in the media, and the way that that was so poetically tied in, visually stuck with me,” she said. “It was the first time I recognized a political message being articulated through art. For that reason, it stuck with me that bees were a form of strong symbolism tied to resilience."
Living in Charlotte, North Carolina, Dunlap became a certified beekeeper under the Mecklenburg County Beekeepers Association in 2017. She continued practicing as she moved around the country, with stops in Chicago and Denver, eventually landing in Atlanta in 2021. Looking for a way to connect to the local beekeeping community, she attended an April presentation by UHBP Director Jennifer Leavey, who offered Dunlap a chance to get involved at Georgia Tech.
She now handles the inspection of the hives on The Kendeda Building roof, where she monitors for pests and ensures the bees have proper nutrition to sustain their population through the seasons. The UHBP began in 2012 with the goal of educating the Tech community on the importance of these pollinators within the Atlanta ecosystem and beyond — a charge that Dunlap carries on.
Over the next year, she will continue working on her sound art project that examines the frequency at which bees “buzz” and how it, along with the responsibilities of beekeeping, is being used by VA hospitals and programs to ease the effects of PTSD. While the science behind the connection is still being explored, beekeeping was recommended more than a century ago — to soldiers returning home from World War I — according to a CNBC profile of Bees4Vets, a nonprofit based in Nevada.
Whether it was baking sourdough bread or learning a new language, many people, including Dunlap, took the early days of the Covid-19 pandemic to pick up a new hobby. She began a master's program at the School of the Art Institute of Chicago with the goal of using beeswax in encaustic painting, which uses hot wax mixed with pigments. The use of natural materials collected through her beekeeping practice connects Dunlap to her work.
“It's a way of tapping into another level of consciousness. It's a way of articulating the noncommunicable relationship between me and the bees. When there's a language gap between people, we try to fill it in with translation, but without a direct way to translate the language or the sensation that I feel from the bees, this allows me to document my practice in an abstract form,” she said.
By layering the wax and applying heat throughout the process, Dunlap watches the pieces take shape, often with the unpredictability of an active hive, as she says the art “can create itself.” She collects the wax in small amounts, knowing that she can only produce her art if the bees are healthy.
"It's an eco-conscious practice, making sure I don't use more than I need," she explained. “I love the landscape it creates, and it's all about me creating a direct relationship with my medium and knowing that I earned it by developing a relationship with the bees."
As Dunlap continues her year-long residency with the UHBP, she intends to help educate the community, both on campus and around the Atlanta area, in the hopes that more prospective beekeepers will explore their curiosity to unlock the full potential of the practice.
"It's been a practice that keeps unveiling itself to me," she said. "As you get more engaged, you learn there is so much more to it than just the day-to-day hive inspections. There is a lot of beauty to it as well."
Students at Tech have several ways to get involved with research and beekeeping, including the Living Building Science VIP team, the Beekeeping Club, and various classes and workshops hosted by the UHBP.
]]>That’s how Rachel Moore describes the view from the top of the Greenland Ice Sheet. “It's a really challenging environment, but it was really, really interesting to be there. I was there for nearly 50 days.”
Moore is an expert at collecting data in difficult research environments, traveling to some of the most extreme places on Earth in order to research microbes, and what hints they might give regarding astrobiology.
“It all started in grad school, when I joined a microbial ecology lab,” Moore recalls. “I pretty quickly learned that I love to do really difficult, challenging projects. I got interested in working around fire, biomass burning and forests, and I started collecting bacteria from the air. That was a challenge in and of itself, just trying to collect these really tiny things while standing in the smoke from the forest fires. But from that I learned that I loved to go out into the environment and collect things and try to understand everything around me.”
“I have a lot of different projects, but they all connect through astrobiology,” Moore says. “I’m interested in anything that hasn't been answered yet.” Moore is also leading a project called EXO Methane, which is investigating if different Archaea could survive in Martian and Enceladus-like environments. She’s also collaborating on a project that will send a probe to Venus next year.
Moore started her postdoctoral research at Georgia Tech, and is now continuing her work as a Research Scientist in the same laboratory. “The first project I started in this lab focused around how microbes can survive a really, really dry environment,” she adds. To study this, Moore traveled to the Atacama desert in Chile — the driest place on Earth, and also one of the best analogs to the surface of Mars. “What we were interested in there is how organisms survive intense radiation and intense desiccation. And how does that change as you look at different sites in the Atacama?”
Then, this past summer, Moore traveled to another extreme environment — Greenland. “Instead of being hot and dry, Greenland is extremely cold and dry,” Moore explains. “So it was similar in some aspects, but completely different in terms of logistics and sampling methods. Because we were there in the summer, the sun never set. We were also at high elevation — 10,530 feet above sea level.”
The project was started by Nathan Chellman and Joe McConnell from the Desert Research Institute (DRI), and Moore’s role this year was to investigate the microbiology component of the research. “They had been seeing some anomalies in methane and carbon monoxide in ice samples,” Moore says. “We were curious if microbes might be producing some of this, either in the ice core after it’s been sampled, or while it’s still in the glacier.”
“The microbes would not be swimming around or anything” in the ice cores, Moore explains, “but it’s possible that their metabolism is still active, and they’re potentially able to make some of the gases, like methane, in this frozen environment. Our goal was to measure these things in the environment.”
Gathering samples wasn’t easy. “We set up a lab on the glacier, and we set it up in a trench to try to keep any of the ice cores that we pulled out roughly at the same temperature as the glacier itself,” Moore says. Because of that, “weather was a huge, huge thing. Anytime it would get stormy, the wind would blow all of the snow around, and it would fill the entrance to our trench. We had to dig ourselves out several times. People would put out flags so that you could see your way back to the main house or back to your dorms.”
The team hopes that this research will give a more defined record of the past from the Greenland Ice Sheet, improving climate change predictions. Moore also notes applications in astrobiology, adding that “there are a lot of icy worlds like Mars, Enceladus, and Europa, with either an icy crust over the ocean or glaciers on the northern and southern poles.”
Moore was also able to test new technology in the field, using a tool built by Georgia Tech undergraduates alongside her advisor Christopher Carr, assistant professor in the School of Earth and Atmospheric Sciences. An ice melter that can be used to take and clean ice samples, the tool is a miniaturized prototype that may be able to help take measurements on Mars, or in similar remote environments in the future.
“Being able to take a tool that Georgia Tech undergraduates made to Greenland and test it on 600-year-old ice in the field was a really cool experience,” Moore adds. “We brought Starlink with us, and so I was able to video call the undergraduate team while I was testing their tool, which was really special.”
The team is now lab-analyzing ice cores that they brought back from Greenland, unraveling which microbes might be present and potentially active. “It's really interesting to see: Is this all chemistry? Is it biology based? Or is there some intersection of the two?” Moore says. “Maybe there's some chemistry or photochemistry happening, plus some biology happening. Whatever it is, we'll have to wait and see.”
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