Deep beneath the icy waters of the Antarctic Peninsula, a tiny marine creature called an ascidian—a sea squirt no bigger than a marble—may hold the key to a new melanoma treatment. In 2026, researchers from the University of South Florida, including diving safety officer Ben Meister and postdoctoral researcher Sam Afoullouss, returned from a grueling six-week expedition in one of Earth's most remote and treacherous environments to study this organism and the bacterium living inside it, a bacterium capable of killing melanoma cancer cells without harming healthy human tissue.
The story of this discovery spans two decades. USF chemistry professor Bill Baker first identified the organism's cancer-fighting potential 20 years ago and has been piecing together its secrets ever since. What makes this organism extraordinary is the selectivity of its weapon: the bacterium produces a compound that hunts down melanoma while leaving normal cells untouched—a precision that most cancer drugs struggle to achieve. "More than half of FDA-approved drugs originate from natural sources," Baker explained. "We first discovered this ascidian produces a bacterium that contains a toxic compound that kills melanoma cancer cells while not harming normal human cells. That selectivity is critical in drug development because you want to treat the disease without harming the patient."
Antarctica itself was the driving force behind this expedition. The continent has been geographically and environmentally isolated for millions of years, allowing species there to evolve independently and develop highly specialized adaptations. The ascidians studied by the Baker Lab exist nowhere else on Earth. "The continent is unique because it has been geographically and environmentally isolated for millions of years," Baker said. "As a result, species in Antarctica have had time to evolve independently, leading to highly specialized organisms."
The expedition's focus was specific and urgent: determining where exactly the melanoma-killing bacterium occurs within the ascidian, how widespread it is, and how it functions inside its host organism. These ascidians typically inhabit depths between 18 and 24 meters—roughly 60 to 80 feet—clinging to sloped or vertical seafloor surfaces where strong currents deliver the nutrients they need to survive. Collecting samples required meticulous planning. Divers made multiple dives averaging 8 to 11 minutes each, descending to maximum depths of about 40 meters. The Antarctic environment demands unforgiving attention to detail: leopard seals patrol nearby, ice breaks unpredictably, visibility shifts without warning, and the sea never forgives carelessness. The team also deployed two remotely operated vehicles to explore deeper waters and map the ascidians' distribution across different depths and locations.
The work didn't end when the expedition team climbed back onto solid ground. The specimens collected now move through months or even years of rigorous analysis—DNA sequencing, chemical assessment, and biological testing—divided among multiple expert teams. This painstaking process is essential for understanding how the compound actually works and whether it can eventually be developed into a viable drug. Baker's laboratory track record suggests promise: his previous marine discoveries have already led to patented compounds with potential applications against drug-resistant malaria, various cancers, and antibiotic-resistant infections. The ascidian samples from Antarctica may prove to be the next chapter in that story, potentially offering hope to the hundreds of thousands of people diagnosed with melanoma each year.