Quorum sensing molecules (QSMs) regulate, through a chemical communication process, multiple complex systems in bacterial and some fungal populations on the basis of cell density. The bacterial QSMs involved in inter-kingdom cross-talk may exhibit antagonistic activity against fungi. This provides an important opportunity for biocontrol of fungal invasion in plants. It has been shown that cultures of Bacillus spp. inhibit fungal growth. Here, we explore the inhibitory potential of the industrial workhorse Bacillus licheniformis NCIMB-8874 and its QSM (ComX pheromone) on the growth of Aspergillus flavus, a cereal, legume, and nut crop pathogen. Our studies show that ComX filtered extracts from cultures of B. licheniformis can cause a significant reduction in the growth of A. flavus NRRL 3357 and ESP 15 at a concentration as low as 13 mu g ml(-1). This work evidences, for the first time, the inter-kingdom utility of the bacterial quorum sensing ComX pheromone indicating potential antifungal food security against A. flavus.