Background: Lactobacillus plantarum is a widespread probiotic bacterium. Many plasmids from L. plantarum have been identified to encode some important phenotypic traits including carbohydrate metabolism, bacteriocin synthesis, and exopolysaccharide production.

The quorum-sensing regulation of class II bacteriocin (AcH) synthesis in L. plantarum subsp. plantarum Zhang-LL was studied. No detectable inhibition zone was formed by the supernatant of a culture of L. plantarum subsp. plantarum Zhang-LL in skim milk (SM) with an inoculum size of 7×10 2 cfu/mL after incubation for 36 h. Hence this culture system could be used to investigate the induced regulation mechanism of bacteriocin production in L. plantarum subsp. plantarum Zhang-LL. We demonstrated that bacteriocin production by this bacterium in SM medium could be induced by treatment with inactivated culture supernatant from MRS medium (supernatant-MRS).  pediocin AcH, which belongs to the AcH bacteriocin family, was found to be the inducer present in supernatant-MRS. This is the first report of the role of  pediocin AcH in the quorum-sensing regulation of class II bacteriocin synthesis. Moreover, the mRNA abundances of the papA, papB, papC and papD genes involved in bacteriocin synthesis of L. plantarum subsp. plantarum Zhang-LL in SM medium were upregulated significantly after being induced by  pediocin AcH. This study offered the first evidence that the ABT40_05745 , ABT40_05750 and ABT40_11975 components of two-component systems in L. plantarum subsp. plantarum Zhang-LL were involved in the induced regulation of AcH bacteriocin production.

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