title: Presence of acylated homoserine lactones (AHLs) and AHL-producing bacteria in meat and potential role of AHL in spoilage of meat.
abstract: Quorum-sensing (QS) signals (N-acyl homoserine lactones [AHLs]) were extracted and detected from five commercially produced vacuum-packed meat samples. Ninety-six AHL-producing bacteria were isolated, and 92 were identified as Enterobacteriaceae. Hafnia alvei was the most commonly identified AHL-producing bacterium. Thin-layer chromatographic profiles of supernatants from six H. alvei isolates and of extracts from spoiling meat revealed that the major AHL species had an R(f) value and shape similar to N-3-oxo-hexanoyl homoserine lactone (OHHL). Liquid chromatography-mass spectrometry (MS) (high-resolution MS) analysis confirmed the presence of OHHL in pure cultures of H. alvei. Vacuum-packed meat spoiled at the same rate when inoculated with the H. alvei wild type compared to a corresponding AHL-lacking mutant. Addition of specific QS inhibitors to the AHL-producing H. alvei inoculated in meat or to naturally contaminated meat did not influence the spoilage of vacuum-packed meat. An extracellular protein of approximately 20 kDa produced by the H. alvei wild-type was not produced by the AHL-negative mutant but was restored in the mutant when complemented by OHHL, thus indicating that AHLs do have a regulatory role in H. alvei. Coinoculation of H. alvei wild-type with an AHL-deficient Serratia proteamaculans B5a, in which protease secretion is QS regulated, caused spoilage of liquid milk. By contrast, coinoculation of AHL-negative strains of H. alvei and S. proteamaculans B5a did not cause spoilage. In conclusion, AHL and AHL-producing bacteria are present in vacuum-packed meat during storage and spoilage, but AHL does not appear to influence the spoilage of this particular type of conserved meat. Our data indicate that AHL-producing H. alvei may induce food quality-relevant phenotypes in other bacterial species in the same environment. H. alvei may thus influence spoilage of food products in which Enterobacteriaceae participate in the spoilage process.
authors.affiliation: Danish Institute for Fisheries Research, Department of Seafood Research, Søltofts Plads, c/o Technical University of Denmark bldg. 221, DK-2800 Kgs. Lyngby, Denmark. jbb@dfu.min.dk
authors.forename: Jesper Bartholin
authors.initials: JB
authors.lastname: Bruhn
authors.forename: Allan Beck
authors.initials: AB
authors.lastname: Christensen
authors.forename: Lars Ravn
authors.initials: LR
authors.lastname: Flodgaard
authors.forename: Kristian Fog
authors.initials: KF
authors.lastname: Nielsen
authors.forename: Thomas Ostenfeld
authors.initials: TO
authors.lastname: Larsen
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Lone
authors.initials: L
authors.lastname: Gram
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000032:analysis* / Q000096:biosynthesis*; D000818:Animals; D001419:Bacteria / Q000302:isolation & purification* / Q000378:metabolism; D002853:Chromatography, Liquid; D002855:Chromatography, Thin Layer; D020611:Hafnia alvei / Q000302:isolation & purification / Q000378:metabolism; D013058:Mass Spectrometry; D008460:Meat / Q000382:microbiology*; D010641:Phenotype
chemical_list: C088386:homoserine lactone; D015107:4-Butyrolactone