Limited information is available regarding the secretion of signaling molecules by Bacillus subtilis under non-contact coculture conditions to induce bacteriocin Paracin 1.7 production by Lacticaseibacillus paracasei HD1.7 through intercellular communication. We here cocultured L. paracasei HD1.7 with a B. subtilis cell-free supernatant. Paracin 1.7 production was increased by 87.14%, and prcK and prcR expression was increased by 1.75 and 1.39 times, respectively. The metabolic pathways of L. paracasei HD1.7 (histidine metabolism; pyrimidine metabolism; alanine, aspartate, and glutamate metabolism; and amino acid biosynthesis) were affected, which accelerated the production of some nucleotides and their derivatives. Therefore, the fermentation fluid environment of L. paracasei HD1.7 changed because of the addition of signaling molecules secreted by B. subtilis. The metabolism of amino acids, purine, and pyrimidine was altered, thereby indirectly affecting bacteriocin production. The aforementioned results indicate that a heterozygous quorum sensing system is involved in Paracin 1.7 production by L. paracasei HD1.7. This study offers theoretical support for the future industrial development of the novel natural bacteriocin by lactic acid bacteria by optimizing the coculture technology.