There is much interest in the role of microbial community composition in determining ecosystem processes but the role of interactions within these communities has often been underrepresented. One interaction within microbial communities is quorum-sensing, a type of density-dependent cell-to-cell communication. Here we examine the potential of quorum-sensing effects on litter decomposition in two communities (Forest and Meadow) by adding an enzyme that reduces quorum-sensing. The source of the community and quorum-sensing interacted to determine cumulative litter decomposition. Within the meadow community, enzyme additions caused no effect on decomposition, but in the forest community, inhibition of quorum-sensing resulted in a 14–17% decrease in decomposition. We suggest that quorum-sensing, a community interaction, may be an important determinant of litter decomposition in forested systems.