title: Autoinducer-2 properties of kimchi are associated with lactic acid bacteria involved in its fermentation.
abstract: Bacteria use the cell density-dependent quorum signalling system to regulate particular gene expressions. In food microbiology, signalling is well known for its relation to (foodborne) pathogenicity, food spoilage, and biofilm formation. Quorum quenching and inhibition are thus being considered as a feasible approach in food preservation and safety. In the case of the luxS-mediated universal quorum sensing using autoinducer-2 (AI-2), however, it could be a different issue. Several studies have reported a luxS AI-2 synthase homologue in numerous bacteria, comprising both pathogens and beneficial strains. A recent study has shown the AI-2 signal to restore the balance of the major phyla of the gut microbiota in antibiotic-induced dysbiosis. We measured the AI-2 activity of the lactic fermented food, kimchi, and found different AI-2 signalling intensities. In order to trace the origin of the signal production, we obtained 229 lactic acid bacterial isolates from the kimchi samples, and detected the AI-2 properties of each isolate using a modified AI-2 bioluminescence assay. Our results showed isolates of dominant species of the genera Lactobacillus, Weissella and Leuconostoc which either produced or inhibited the AI-2 signal. No isolate of the dominant species Lactobacillus sakei (75 isolates) and Lactobacillus curvatus (28 isolates) showed AI-2 producing activity, while AI-2 inhibition could not be detected for any of the 31 Lactobacillus plantarum isolates. These results suggest the AI-2 activity of kimchi to result from the interaction of the associated microbial food cultures (MFCs) during fermentation. Thus far, only sparse information is available on AI-2 signalling interaction in fermented food, however, we suggest that fermented food may be a supplier of AI-2 signalling molecules via typical MFCs.
authors.affiliation: School of Life Sciences, Handong Global University, Pohang, Gyeongbuk 791-708, South Korea; Graduate School of Advanced Green Energy and Environment (AGEE), Handong Global University, Pohang, Gyeongbuk 791-708, South Korea.
authors.forename: Hyunjoon
authors.initials: H
authors.lastname: Park
authors.affiliation: School of Life Sciences, Handong Global University, Pohang, Gyeongbuk 791-708, South Korea.
authors.forename: Heuynkil
authors.initials: H
authors.lastname: Shin
authors.affiliation: School of Life Sciences, Handong Global University, Pohang, Gyeongbuk 791-708, South Korea; Graduate School of Advanced Green Energy and Environment (AGEE), Handong Global University, Pohang, Gyeongbuk 791-708, South Korea.
authors.forename: Kyuyeon
authors.initials: K
authors.lastname: Lee
authors.affiliation: Graduate School of Advanced Green Energy and Environment (AGEE), Handong Global University, Pohang, Gyeongbuk 791-708, South Korea. Electronic address: wilhelm@woodapple.net.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Holzapfel
mesh_terms: D005285:Fermentation; D005516:Food Microbiology; D006714:Homoserine / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D056546:Lactobacillales / Q000235:genetics / Q000378:metabolism*; D007783:Lactones / Q000378:metabolism*; D056265:Microbial Interactions / Q000502:physiology
chemical_list: D007783:Lactones; C091088:N-octanoylhomoserine lactone; D006714:Homoserine
keywords: Autoinducer-2; Fermented food; Kimchi; Lactic acid bacteria (LAB); Quorum sensing