Presence of acylated homoserine lactones (AHLs) and AHL-producing bacteria in meat and potential role of AHL in spoilage of meat.
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.
Bruhn
Jesper Bartholin
JB
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
Christensen
Allan Beck
AB
Flodgaard
Lars Ravn
LR
Nielsen
Kristian Fog
KF
Larsen
Thomas Ostenfeld
TO
Givskov
Michael
M
Gram
Lone
L
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
C088386:homoserine lactone; D015107:4-Butyrolactone