Control of Listeria monocytogenes biofilm by paenibacterin, a natural antimicrobial lipopeptide

- Small concentrations (<10 μg/mL) of paenibacterin suppressed biofilm formation by Listeria monocytogenes at 35 °C and 37 °C.
- Paenibacterin treatment (6.8 μg/mL), for up to 6 h, disrupted biofilms preformed at 35 °C, but not those preformed at 37 °C.
- Supporting evidence came from UV microscope images of treated biofilm, motility inhibition, and gene downregulation data.

Paenibacterin is a novel antimicrobial lipopeptide produced by Paenibacillus thiaminolyticus. The present study assesses the efficacy of paenibacterin in inhibiting Listeria monocytogenes biofilm formation and removing established biofilm. Paenibacterin at 1.7 μg/mL (less than compound's minimum inhibitory concentration, MIC) and higher concentrations (3.4 μg/mL, 6.8 μg/mL) were tested. Concentrations greater than the lipopeptide's MIC significantly inhibited the formation of L. monocytogenes biofilm on polystyrene microtiter plates at 30 °C and 37 °C. Paenibacterin also was added to established biofilm and its structure or removal was monitored by fluorescence microscopes after appropriate staining. Results show that paenibacterin could eliminate established biofilms formed at 30 °C for 72 h, whereas it could not disrupt stronger biofilms formed at 37 °C for 72 h. Motility of L. monocytogenes is important for its ability to form biofilm. Swimming assay confirmed that paenibacterin suppressed L. monocytogenes motility. Real time quantitative PCR data revealed that paenibacterin down-regulated L. monocytogenes critical biofilm-associated genes, prfA, agrA, flaA, fliG and flgE. These results suggested the feasibility of using paenibacterin in food processing environments to control L. monocytogenes growth and biofilm formation, or even for removal of some established biofilms.