Fermented foods like yogurt, soy sauce, and kimchi rely on the actions of microbes for their unique properties and flavor profiles. One way these microbes may interact to influence fermentation is by exchanging genes in a process known as horizontal gene transfer, which involves small DNA sequences called mobile genetic elements (MGEs) that can move from one place to another. To learn more about how MGEs impact fermentation-associated microbes, scientists profiled the genetic material of the bacterial communities in over 500 samples representing 25 fermented food types, finding MGEs were widely distributed among them. These MGEs were often located near functional genes, particularly biosynthetic gene clusters, whose products are not directly involved in microbial growth but play crucial roles in communication and competition between species. These clusters were more active when a greater number of MGEs were found nearby, enhancing the competitive ability of certain strains of a bacterial species over other strains. These findings reveal the previously unrecognized importance of MGEs in the bacterial communities responsible for food fermentation and lend crucial new insight into how MGEs could drive microbial interactions in other types of ecosystems.