In cows and other ruminants, microbes in a specialized organ called the rumen metabolize ingested food into usable energy. During this process, the rumen microbes form a glue-like layer called a biofilm on the ingested plant material. This biofilm formation requires quorum sensing (QS), a type of intercellular communication by which the microbes synchronize their gene expression and behaviors. However, QS in complex real-world communities like the rumen remains poorly understood. To learn more, researchers recently analyzed nearly 1000 genomes of rumen microbes. They found 8 types of genes encoding known QS signaling molecules and about three-fourths of the genomes contained QS-related genes. In particular, 680 bacterial genomes contained genes for proteins that synthesize or respond to the QS signaling molecule AI-2. Further analyses suggested that AI-2 receptors containing a region called the dCache_1 domain might be essential for rumen microbes’ coordinated behaviors. In particular, AI-2 might act as a universal regulator by binding to the dCache_1 domain to activate various QS signaling pathways. Notably, experimental studies are needed to supplement these sequence-based findings. Nevertheless, this study provides insights into how microbes use QS to coordinate their plant-digesting activities in the rumen.