Growth-Dependent Paenibacillin Biosynthesis and Its Association with an Agr-like Quorum Sensing System in...

Antimicrobial resistance in foodborne pathogens and demand for clean-label foods highlight the need for natural antimicrobial preservatives. Paenibacillin, an antimicrobial peptide produced by Paenibacillus polymyxa OSY-DF, has potential as a natural preservative, but low productivity limits its application. Paenibacillin is encoded by an 11-gene biosynthetic gene cluster (BGC) containing seven biosynthetic genes and a putative accessory gene regulator (Agr)-like quorum sensing (QS) locus (agrABCD). Understanding the association between QS systems and paenibacillin biosynthesis may provide insights into factors influencing its production.

The Agr-like QS system was assessed through a time-course transcriptional analysis of the paenibacillin BGC and antimicrobial bioassays. AI-2 activity was detected using Vibrio harveyi, and its potential regulatory role was assessed by inhibiting AI-2 signaling with D-ribose.

Transcription of agrABCD increased after 4 h, reaching 18.59- to 202.61-fold upregulation at 24 h relative to 0 h. In contrast, limited transcription of the seven biosynthetic genes was detected during the initial 8 h, followed by 19.64- to 136.12-fold upregulation at 24 h. Anti-Listeria activity was first detected at 12 h and increased through 24 h. These transcriptional and phenotypic patterns suggest a potential association between the Agr-like QS system and paenibacillin BGC expression. AI-2 was detected in OSY-DF culture supernatants; however, reducing AI-2 signals did not reduce paenibacillin activity.

Paenibacillin production is growth phase-dependent and temporally associated with Agr-like gene transcription, whereas AI-2 does not appear to regulate its biosynthesis. Functional validation through targeted agr disruption is required to define the direct regulatory role of the Agr-like QS system.