Lucinid clams, inconspicuous inhabitants of the seafloor and one of the most diverse group of animals in the ocean, rely on symbiotic bacteria for their survival. Researchers now reveal the evolutionary journey of these tiny tenants. Faced with a drastically changing environment following the closure of the Isthmus of Panama, they acquired new metabolic skills to enable their own survival. Understanding the adaptive strategies of bacteria provides insight into their potential responses to challenging environmental changes, such as those caused by human activities.